keep it simple science
TM
Baulkham Hills High School SL#802445
HSC Biology Topic 1
MAINTAINING A BALANCE
What is this topic about? To keep it as simple as possible, (K.I.S.S.) this topic involves the study of: 1. THE FUNCTION OF ENZYMES & HOMEOSTASIS 2. TEMPERATURE REGULATION IN ORGANISMS 3. INTERNAL TRANSPORT SYSTEMS IN ORGANISMS 4. EXCRETION & WATER BALANCE
but first, an introduction... Living Things are Made of Cells
Homeostasis
All living things are composed of microscopic units called cells. You learned in a previous topic about the structure of a cell and the functions of the organelles.
The enzymes that control all the chemical reactions in every living cell are very sensitive to the temperature and the pH (acidity) of the surroundings. It is vital that the “internal environment” of any organism is kept as constant as possible so that the enzymes and the chemistry of each cell keep operating normally.
GENERALIZED DIAGRAM OF A LIVING CELL Organelles
The process of “keeping everything the same” is called homeostasis, and is one of the most important and vital processes in every organism. In this topic you will study some of the basic mechanisms of homeostasis, and how certain body systems are involved by absorbing, transporting, regulating and excreting the vital chemicals of life. “Membrane” on the outside contains the cell , and controls what goes in or out
Nervous System Regulates body temperature
Cytoplasm
jelly-like liquid fills the cell Circulatory System transports gases, nutrients & wastes
Each cell is “alive” in its own right, and capable of all the life functions:• growth • reproduction • movement • assimilation • response to changes in its environment
Respiratory System Gas exchange
Excretory System Regulates water balance and excretes metabolic wastes
Metabolism is Chemistry Controlled by Enzymes What goes on inside a living cell is mainly a matter of chemical reactions... new molecules are built, others are torn apart. Special reactions release the energy needed to make all this chemistry happen. In this topic you will learn about the importance of Enzymes... the special molecules that control the chemistry of each cell. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
As well as the homeostatic processes in mammals and some other animals, you will study some regulatory processes in plants. 1
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
CONCEPT DIAGRAM (“Mind Map”) OF TOPIC Some students find that memorizing the OUTLINE of a topic helps them learn and remember the concepts and important facts. As you proceed through the topic, come back to this page regularly to see how each bit fits the whole. At the end of the notes you will find a blank version of this “Mind Map” to practise on. Effects of Temp, pH & substrate conc. on enzyme activity Concept of Negative Feedback
Endotherms Ectotherms
Receptor, Control Centre Effectors
Shape & specificity of Enzymes
Temperature range of life
Processesses of heating & cooling
Plants
Temperature regulation in...
Hypothalamus & Effector Organs
Enzymes & Homeostasis
Temperature Regulation in Organisms
Functions & characteristics of Enzymes
MAINTAINING A BALANCE
Coping with salt
Blood & Blood Vessels
Water conservation in Aust. Plants
Excretion & Water Balance Water Balance in Aust. insects & mammals
Transport in Plants
HSC Biology Topic 1 copyright © 2005-2007
How the gases are carried
Kidney & Nephron Structure & Function
Oxygen saturation
Translocation in Phloem
Enantiostasis
Homeostasis ADH & Aldosterone
Internal Transport Systems
Importance of water & Water Balance
Dialysis & HRT
Transpiration in Xylem
Excretion Filtration & Reabsorption
keep it simple science
2
Substances carried in blood. Where from, where to?
Artificial blood?
Importance of Haemoglobin
Blood products
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
1. THE FUNCTION OF ENZYMES & HOMEOSTASIS The Importance of Shape Many of the properties of enzymes are related to their precise 3-dimensional shape.
Metabolism is Chemistry Everything that happens inside a living thing is really a matter of cell chemistry... “metabolism”. For example...
The shape of the enzyme fits the “substrate” molecule(s) as closely as a key fits a lock.
• In order to move, protein fibres inside muscle cells must be made to slide past each other. This is achieved by chemical reactions occurring along the muscle fibres. • For your body to grow, cells must divide and add more membranes, cytoplasm and organelles to increase the cell size. This involves the chemical construction of new DNA molecules, new phospholipids for membranes and so on.
Various
Enzyme
Only this one fits
• All these chemical reactions require energy. Energy is delivered by the ATP molecule, itself the product of a series of chemical reactions in the mitochondria... cellular respiration.
This is why enzymes are “substrate-specific”... only one particular enzyme can fit each substrate molecule. Each chemical reaction requires a different enzyme.
Enzymes
Changes in temperature and pH (acidity) can cause the shape of the enzyme to change. If it changes its shape even slightly, it might not fit the substrate properly any more, so the reaction cannot run as quickly and efficiently. This is why enzymes are found to work best at particular “optimum” temperature and pH values.
Every one of these reactions requires a catalyst... a chemical which speeds the reaction up and makes it happen, without being changed in the process. In living cells there is a catalyst for every reaction type. Biological catalysts are called enzymes, and: • are protein molecules (made of folded chains of amino acids) • have a particular 3-dimensional shape, which fits the “substrate” molecule(s) of the reaction • are highly “substrate-specific”. This means that each enzyme will only catalyse one particular reaction, and no other. • will only work effectively in a relatively narrow range of temperature and pH (acidity).
Substrate...
Enzyme shape at optimum pH and temperature
Shape changes slightly at different pH or temp.
...ENZYME molecule
Twists & folds Polymerization
Enzyme’s “Active Site” has a shape to fit the substrate(s) exactly
ENZYME
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
...no longer fits enzyme
Protein, with precise 3-D D shape...
Polypeptide chain
Substrate molecules are chemically attracted to the enzyme’s active site
Substrate Molecules
All of these reactions, and more, add up to “metabolism”: the sum total of all the thousands of chemical reactions going on constantly in all the billions of cells in your body.
Amino acid molecules
Different
Substrate molecules brought together and react with each other
ENZYME
3
Product released from enzyme
ENZYME can react with more substrate
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
The pH Scale
Optimum Temperature Not all enzymes will “peak” at the same temperature, or have exactly the same shape graph. In mammals, most enzymes will peak at around the animal’s normal body temperature, and often work only within a narrow range of temperatures.
The acidity or alkalinity of any solution or environment is measured on a numerical scale known as “pH”. On the pH scale, anything which is neutral (neither acid nor alkaline) has a pH = 7. increasing acidity 3
4
increasing alkalinity
Neutral
5
6
7
8
9
10
An enzyme from a plant may show a much broader graph, indicating that it will work, at least partly, at a wider range of temperatures.
11
An enzyme from a thermophilic bacteria from a hot volcanic spring will show a totally different “peak” temperature, indicating that its metabolism will perform most efficiently at temperatures that would kill other organisms.
The inside environment of a cell, and most parts of an organism’s body, is always very close to pH 7... i.e. neutral. An exception is in the digestive system where conditions are usually quite strongly acidic in the stomach (approx. pH 2).
Enzyme Activity Graphs You will have carried out experimental work to measure the “activity” of an enzyme under different conditions of temperature, pH and the concentration of the substrate chemical.
Reaction Rate
Mammal Enzyme
You may have measured the rate of a chemical reaction being catalysed by an enzyme, such as: • the rate of milk clotting by rennin (junket tablets) • the rate of digestion of some starch by amylase • the rate of decomposition of hydrogen peroxide by “catalase” enzyme.
Plant Enzyme
0
A common way to measure the rate of a reaction is to measure the time taken for a reaction to reach completion... the shorter the time taken, the faster the reaction. This why the reciprocal of time taken (1/time) is used as the measure of rate of reaction.
20
40
60
Temperature
80
100
(oC)
The graph of reaction rate (or “enzyme activity”) against temperature is usually not symmetrical. It tends to rise gradually at temperatures below the optimum, but often falls more steeply at temperatures above optimum, because the denaturation of the enzyme can lead to a rapid decline in activity.
The Effect of Temperature When enzyme activity is measured over a range of temperatures, the results produce a graph as below.
1/time taken for reaction (rate)
Thermophilic bacteria enzyme
Explanation: As temperature rises the rate increases because the molecules move faster and are more likely to collide and react. All chemical reactions show this response.
Experimental Points
However, beyond a certain “peak” temperature, the enzyme’s intricate shape begins to be distorted. The substrate no longer fits the active site so well, and the reaction slows. If the temperature was lowered again, the enzyme shape, and reaction rate could be restored. If the temperature reaches an extreme level, the distortion of the enzyme’s shape may result in total shut-down of the reaction. The enzyme may be permanently distorted out of shape, and its activity cannot be restored. We say the enzyme has been “denatured”. Temperature
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
4
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
The Effect of Substrate Concentration
The Effect of pH When the temperature is kept constant and the enzyme tested at various pH levels, the results will produce a graph as shown. 1/time (rate) Enzyme Activity
Generally in any chemical reaction occurring in solution the rate of the reaction increases if the concentration of the reacting chemical(s) is increased. The explanation is simply that if the molecules are more concentrated, then it becomes more likely that they will collide and react with each other.
2
3
4
5
7
6
8
9
Reaction Rate
When an enzyme is involved, the situation is a little more complicated:
10 11 12
pH
Generally, all intra-cellular enzymes (i.e. those from within a cell) will show peak activity at a pH close to neutrality... their optimum pH is close to 7.
Substrate Concentration
The digestive enzyme “pepsin” from the stomach shows an optimum pH about 2 or 3, allowing it to work best in the acidic environment.
Initially the rate of the reaction increases as the substrate concentration goes up, just as it does with any reaction.
Intra-cellular enzyme
Soon though, the graph begins to flatten out and level off because the enzyme molecules are “saturated” with substrate and cannot work any faster.
Pepsin. (Stomach enzyme) Enzyme Activity
If, at this point, you were to add more enzyme then the reaction rate would once again go up. It would level off again as the enzyme molecules were once again swamped and saturated with the substrate.
1
2
3
4
5
6
7
8
9
10 11 12
Extra enzyme added
pH
Reaction Rate
The shape of the pH graph is usually symmetrical on either side of the “peak”... optimum pH. The explanation for the shape is as follows: • at the optimum pH the enzyme’s 3-D shape is ideal for attracting the substrate, so reaction rate is maximum • at any pH higher or lower than optimum, the enzyme’s shape begins to distort, and reaction rate declines as the substrate no longer fits so perfectly.
Substrate Concentration
• at extremes of pH, the enzyme can be irreversibly denatured and shows no activity at all. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
5
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Homeostasis
Homeostasis always involves “Negative Feedback”. This is when any change in a system causes a shift in the opposite direction.
Since... • an organism’s metabolism is largely a matter of chemical reactions, and • each reaction is catalysed by an enzyme, and • each enzyme is quite sensitive to temperature and pH
For example, a thermostat control of an oven:
Oven
If temperature is too high
In a “Positive Feedback” system any change re-reinforces itself by causing more change in the same direction.
If temperature is too low
The result is that the temperature of the oven remains fairly stable. It oscillates up and down a little, but always stays close to the temperature the oven was set at.
For example, a fire growing bigger...
produces heat
Temperature Sensor (detector)
NEGATIVE FEEDBACK ACTION
Feedback Mechanisms The mechanism of Homeostasis involves “feedback”... a situation where the result of some action feeds back into the system to cause the next change to the system.
s ol co
NEGATIVE FEEDBACK ACTION
n
As well as regulation of temperature and pH, homeostasis involves the regulation of many other factors such as: • water and salt balance in body fluids • blood sugar levels • oxygen and carbon dioxide levels.
small fire
heat
e Ov
... it follows that the interior environment of the organism’s body and cells must be maintained at stable levels of temperature and pH close to the optimum for the enzymes. The process of maintaining a stable, internal environment is called “Homeostasis”.
Turn heater ON s up
Turn heater OFF
Negative Feedback causes a system to maintain stability.
Heat ignites more fuel
The key parts of a feedback system are: • a receptor, to measure and monitor the conditions • a control centre, which “decides” how to respond, and • effectors, which carry out the commands of the control centre and make the necessary adjustments to the system.
Fire grows larger
Produces more heat
In animals, it is the Nervous System which is largely responsible for carrying out the receptor and control centre functions necessary for many aspects of homeostasis.
Heat ignites more fuel
In mammals, which maintain fairly constant body temperatures, it is the Hypothalamus at the base of the brain which monitors blood temperature and sends out command messages for negative feedback, rather like the oven thermostat system.
Fire grows larger
Positive Feedback always causes a system to grow out of control, or shrink away to nothing
Cerebrum Pituitary Gland
It never results in stability.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
Hypothalamus
Cerebellum Spinal chord
6
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Worksheet 1
3. Sketch a graph of Enzyme activity against pH.
Part A Fill in the blanks. Check your answers at the back. The sum total of all the chemical reactions in an organism’s body is called a)....................................................... Each reaction requires a catalyst, which is a chemical which b)............................................. the reaction, without being c)........................................... itself. Biological catalysts are called d)..................................... These have the following properties: • They are molecules of e)......................................, which are polymers of f)................... ................... • Each one has its own unique g)........................., which perfectly fits the molecule(s) of the reaction. These molecules are referred to as the h).................................. • Because each enzyme only fits its own particular h)............................., they are said to be h)................................ i)............................................... • Enzymes will only work effectively in a narrow range of j)............................................. and k)........................ This is because their l).................................. changes so that they no longer fit their substrate.
4. Explain why the graph shows a “peak” of optimum activity at a certain pH.
5. Why does activity decline at pH values higher or lower than the optimum?
6. Sketch a graph of enzyme activity against substrate concentration.
The pH scale is a numerical measurement of m)...................... and n)...................................... Things that are neutral have a pH= o)............. Acids have pH values p).................... 7, while alkalis (bases) have pH q).......................... The pH inside living cells, and in most parts of an organism’s body is about r)..........., but an exception is the s)............................... which is quite strongly t)..................................... Part B Enzyme Graphs 1. Sketch the shape of a graph of Enzyme Activity against Temperature.
7. Explain a) why the graph rises b) why the graph levels off Part C Fill in the blanks Homeostasis is the process of keeping an organism’s internal environment a)......................................... The factors that need to be maintained include b).................................. and c)................... as well as d)............................. and salt balance, e)...................... .............................. levels and oxygen and carbon dioxide levels.
2. Explain the shape of the graph; a) at temperatures below the “optimum”
Homeostasis involves f)..................................... feedback. The 3 parts of any feedback system are the g)........................................, which measures or monitors conditions, the h)........................................ which decides how to respond and issues commands, and the i)........................................... which carry out the commands. In animals generally it is the j).......................................... system which is largely responsible for monitoring and control. In mammals, homeostasis of body temperature is controlled by the k).............................................. at the base of the l).................................................
b) at temperatures above the optimum.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
7
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
2. TEMPERATURE REGULATION IN ORGANISMS Temperature Control in Mammals
Main Parts of the System Receptor and Control Centre is the Hypothalamus at the base of the brain. Special cells constantly monitor the temperature of blood flowing by. If blood temperature varies by even a fraction of a degree, nerve messages are sent to the effectors. The Effectors include blood vessels, sweat glands, endocrine (hormone) glands, muscles and body hairs.
In a healthy human the internal “core” temperature of the body is about 37oC and is maintained within about 0.5oC at all times. If the body temperature goes up, or down, by more than about 4oC, this is a life-threatening situation. Control of body temperature is achieved as shown in this schematic diagram:
BODY TEMPERATURE REDUCES BLOOD COOLS
to Effectors
Nerve Command
COOLING MECHANISMS Blood vessels dilate Sweat glands activated Hair lowered Metabolic rate reduced
BODY TEMPERATURE TOO HIGH
BODY TEMPERATURE TOO LOW Nerve Command
to Effectors
HYPOTHALAMUS monitors blood temperature
WARMING MECHANISMS Blood vessels constricted Muscles begin “shivering” Hairs erected (goose bumps) Metabolic rate increased
BODY TEMPERATURE INCREASES BLOOD WARMS
How the Effectors Make a Difference
Muscles Nerve signals can cause the skeletal muscles to begin “shivering”. This extra muscle activity generates more heat Blood Vessels Body Hairs to warm the body. Dilation (widening) of veins, Each hair on your body has a tiny muscle arteries and capillaries near the at its base which can cause the hair to Hormones skin allows more blood to flow stand up erect and give you “goose are chemicals which control out near the skin surface. bumps”. This traps a layer of still air various body functions, including This allows more body heat to against the skin and helps insulate and the rate of metabolism and heat escape from the skin, thus production. prevent heat loss. cooling the body. The hormone thyroxine (produced by the thyroid gland in If the hair follicle muscle is relaxed the Constriction (narrowing) of the neck) does exactly that and is hair lies flat and allows more heat loss. blood vessels causes less under the control of the blood to flow near skin. Sweat Glands hypothalamus, via another Less heat flows out to skin When activated, the sweat glands secrete perspiration. hormone from the pituitary to be lost. Body heat is The water evaporates from the skin, carrying away body gland. heat... this has a powerful cooling effect. retained more. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
8
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
The Temperature Range of Life
Temperature Control in Ectotherms
Homeostatic control of body temperature allows an organism to maintain its cells at a temperature close to the optimum for its enzymes. This allows metabolism to run efficiently, despite changes in the surrounding temperature of the environment.
Ectotherms are the “cold-blooded” animals, such as reptiles, amphibians, insects, fish and worms. “Coldblooded” is a misleading term and is best avoided, since these animals are NOT always cold, but rather they rely on the outside environment for their body heat... they do not generate heat internally like a mammal or bird.
However, homeostasis has its limits, and no organism can remain active and thriving under the full range of temperatures of the biosphere of the Earth. Different organisms have adapted to survive in extreme cold environments, or in extremely hot conditions, but never both extremes.
Ectotherms have a variety of adaptations, many of them behavioural, to regulate their body temperature and keep it within the range in which they can be active; generally between 10-30oC. Ectotherms seek, or avoid the heat of the Sun
Extreme Heat There are thermophilic bacteria (members of the Archaea) which live and thrive in volcanic hot springs at temperatures up to 120oC. In terrestrial environments such as hot deserts, the temperature can often reach 40oC and sometimes as high as 60oC. Many plants and animals are adapted to survive these extremes, but few remain active in this heat. Generally in deserts the animals seek shelter and become inactive, while plants shut down their metabolism and merely survive.
Reptiles sun-bake when too cool...
For example, the Blue-Tongue Lizard will lie in a sunny spot with its body flattened and turned side-on to the Sun on a cool morning. This way it absorbs heat more quickly to get its body temperature high enough to become active.
Extreme Cold Once again, there are many organisms which can survive extreme cold, but few that remain active. Certain types of algae and photosynthetic bacteria are found to live within the snow and ice near the poles and are still metabolically active at temperatures as low as -10oC. Below this, the cells become inactive, but survive and re-activate when it warms up again.
As the day becomes hotter, the lizard will turn facing the Sun to absorb less heat, and seek shade to avoid overheating. In prolonged periods of cold weather, such as winter in the Australian Alps, ectotherms cannot be active because the environment cannot supply them with the body heat they need. Animals such as the Copperhead Snake and the Corroboree Frog seek shelter underground and become dormant throughout the winter.
Generally however, plants and animals cannot tolerate their body temperature going below 0oC, since ice crystals forming in cell cytoplasm can destroy membranes and kill cells. Also, the chemical reactions of metabolism run so slowly at low temperature, that life functions are not possible. Of course, many animals do live and survive in the cold because they can produce their own body heat (mammals and birds) and are equipped with body insulation and homeostatic mechanisms to maintain their core temperature despite the cold environment. Perhaps the world champions in this regard are the Emperor Penguins which maintain core body temperatures around +33oC throughout the Antarctic winter in air temperatures as low as -50oC... an amazing difference of over 80oC!
In a process similar to the hibernation of bears, the animal’s heartbeat and breathing slow down, their metabolism almost stops and their body temperature chills to only just above freezing. As long as they are more than about 50 centimetres underground, the ground will not freeze even though buried in snow for several months. If they haven’t burrowed deeply enough they will freeze to death!
Cold Water Environments Even when ice forms on the surface, water environments rarely fall below +4oC, and are remarkably stable in temperature. Life-forms do not need to cope with change, although they may need serious insulation to stay warm. It is the terrestrial environment that is more of a challenge. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
... and seek shelter when too hot
9
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Temperature Control in Endotherms
Responses of Plants to Temperature Change
Endotherms are the animals which produce their own internal body heat and maintain a relatively constant body temperature... the birds and mammals.
Plants cannot respond to temperature change by moving away or hiding. To cope with temperature extremes they must have structural or physiological adaptations.
All endotherms rely heavily on having bodily insulation... fur, feathers or blubber (fat). Humans are endotherms too, but we rely mostly on our technology to provide heaters, air-con, jackets, wetsuits, gloves, etc, to protect our fragile bodies from extreme temperatures. What do other endothermic animals in the wild do?
To cope with seasonal cold weather, many plants (especially in the northern hemisphere) are deciduous... they shed their leaves and basically shut down their metabolism for the winter, rather like an animal hibernating. Their leaves cannot be protected from freezing, so the strategy is to lose the vulnerable parts, survive until next spring, and grow new leaves then.
Firstly, they have all the responses for homeostasis described earlier... dilation or constriction of blood vessels, shivering and sweating etc. As well as these, they may have extra adaptations to help regulate their temperature.
Coping with heat is another story. If there is plenty of water available, such as in a tropical jungle, then the plants cool themselves by allowing maximum evaporative cooling. The leaves open their stomates and allow transpiration to occur. The evaporation has a cooling effect, in the same way that sweating cools an animal.
In hot environments such as the Australian deserts, many mammals such as the Red Kangaroo or the Bilby, have many adaptations to help them cool their bodies:
When it is hot and DRY as well, they have a problem. Desert plants tend to have very small leaves and thick, “stocky” shaped stems. This reduces the surface area being hit by heat radiation from the Sun, and helps prevent overheating. The cacti plant group have taken the strategy to the limit... their leaves are spines, and stems are “fat” and rounded. They are also light coloured to reflect a lot of the radiant heat away.
In the desert, big ears are cool!
Spikes for leaves = lower surface area
Pale colour reflects radiation
• large ears, with good blood supply, increases the surface area for heat loss • like the reptiles, they seek shade in the heat of the day • panting evaporates water from the mouth and throat, and cools the oral membranes which have a rich blood supply. • they may lick their forearms. The evaporation of saliva cools their body in the same way as sweating. (Note: many desert animals lack sweat glands because they cannot afford the water loss of perspiration.)
Low surface area stem
The sclerophyll plants of Australia (gum trees for example) also have small narrow leaves to reduce heat absorption from the Sun. Their other “trick” is to allow the leaves to droop downward. This allows them to catch light for photosynthesis in the cooler mornings when the Sun is low, but avoid absorbing heat when the Sun is overhead in the heat of midday.
In the cold, endotherms go for thick fur coats (Wallaroo) or layers of fat (Australian Fur Seal) to limit the loss of body heat. Penguins, such as the Fairy Penguins along Australia’s southern coast, have a special “blood shunt” in their legs. In warm conditions the shunt is closed and blood flows normally to the feet. Since the feet are about the only part of their body not well insulated, in cold water they could lose a lot of body heat. So in cold water the flow of blood from body toward the feet is “shunted” via a special vein with a valve in it, back into the body. The feet receive virtually no blood, so conserving body heat. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
Narrow, drooping gum tree leaves 10
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Worksheet 2 Fill in the blanks Check your answers at the back.
Animals which can regulate their body temperature are called w)...................................... Examples are the x)................................ and y)........................................ They use all the homeostasis techniques above, and rely on body insulation with fur, z)........................... or aa)................................... as well.
Temperature regulation in mammals is controlled by the a)............................................. at the base of the brain. If body temperature is too high it sends commands to the b)................................ organs to cool the body. Cooling mechanisms include c)............................ of blood vessels to allow d)................... (more/less) blood to flow near skin. Also, the e)............................... glands may be activated, allowing f)............................... to flow. As it g).............................. from the skin, it carries heat away. Metabolic rate may be reduced, to reduce heat production. This is achieved by h)............................. which are control chemicals. An example is Thyroxine, produced by the i)................................... gland.
In extreme environments endotherms may have extra adaptations as well. In Australian deserts many animals have large ab).................... to radiate heat away. They don’t have sweat glands because they can’t afford to ac)............................................................................. but may lick their ad)............................... or pant to achieve some evaporative cooling. In cold environments, thick fur or blubber gives ae)......................................................to retain body heat. The penguins have a special adaptation in the blood vessels to their legs. In cold water, the blood flow to the feet is af)............................................................................. so that less heat is lost through the uninsulated feet.
If the body is too cool, then the hypothalamus commands various warming mechanisms. Blood vessels can be j)........................................... to reduce blood flow to k)............................ Body hairs are l).............................. to trap a layer of still air, which acts to m).............................. better. Nerve commands to muscles can cause them to n)........................................ which produces extra heat. The metabolic rate can be raised by hormones too.
Plants also have many adaptations to cope with temperature extremes. In cold climates many plants are ag)............................................. which means they ah).................................................... in winter. In hot climates with plenty of water, plants open their ai)..................................................... allowing evaporation to cool them. In dry climates, plants cannot afford the water loss, so they have other ways to stay cool without losing water. For example, cacti have aj).......................-shaped leaves to reduce the surface area absorbing heat from direct sunlight. They are often ak)...........................coloured to reflect heat radiation.
Animals which rely on the environment to supply their body heat are called o)........................................... Examples are p)........................................., amphibians, fish etc. In terrestrial environments they often seek or avoid the heat of the q)................ in order to regulate temperature. An Australian example is the r)...................................., which often s)................................ in the morning to warm up, and t)..................................................... when too hot. In cold winters, ectotherms cannot get any heat from the environment and many, such as the u).................................................... survive by v)............................................................ for the winter. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
The Australian al)........................................ plants mostly have am)..................................... (shape) leaves to reduce surface area, and often allow the leaves to an)................................................. (orientation) to avoid the Sun’s heat at midday. WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES
11
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
3. INTERNAL TRANSPORT SYSTEMS IN ORGANISMS Internal Transport in Mammals
Arteries carry blood from the heart out to the body tissues. The walls of an artery are relatively thick and muscular to withstand the high pressure in the blood when the heart pumps.
As is the case with most animals, mammals rely mainly on their Circulatory System for internal transport of substances... their blood, heart and blood vessels; veins, arteries and capillaries. A basic knowledge of how the system operates was covered in Preliminary Topic 2.
Artery walls are very elastic, and when a pulse of high pressure blood passes through, they expand outwards and then contract again, helping to push the blood along. This rhythmic expanding and contracting is what you can feel as your “pulse” wherever an artery is close to the skin, such as in your wrist or throat.
Blood and Blood Vessels You will have examined blood under a microscope and seen something like this:
RED BLOOD CELLS
Veins carry blood back from the body tissues to the heart. The blood here is under lower pressure and the walls of a vein are relatively thin. With little pressure to push blood forward, it is the contraction of the surrounding muscles which helps push the blood along.
Light microscope view
Electron microscope view
Veins may contain valves to prevent back-flow of the blood. VEIN Cross-S Section
ARTERY Cross-S Section
Size = 7 μm
Connective Tissue
blood
You should be able to sketch diagrams of blood cells, and have an idea of their sizes.
blood
Layers of muscle
Sketch of Blood Cells
Side view of VEIN showing a valve.
White Cell much larger than red cells
Blood can flow one way, but not back the other.
Red Cells no nucleus Shaped like a donut with the hole closed over
CAPILLARY Cross-S Section
large, irregular nucleus.
Wall just 1 cell thick for easy diffusion
Ratio: about 600 red cells to 1 white cell
Capillaries are the tiny blood vessels which form a network throughout the tissues so that every living cell is close to the blood supply. The walls of a capillary are only 1 cell thick, so diffusion of substances from blood to cells (or cells to blood) is easily achieved.
Red Blood Cells contain the red pigment haemoglobin, which carries oxygen. This is covered in more detail later. White Blood Cells come in a huge variety of types, but all are involved with defence against disease. This is covered in a later topic.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
blood flow
The inside of a capillary is so small that red blood cells often travel through it in single file. 12
www.keepitsimplescience.com.au
TM
Baulkham Hills High School SL#802445
Substances Carried in the Blood
Changes to the Blood as it Circulates As the blood circulates around the body its chemical composition undergoes a number of changes...
Oxygen O2 is carried in the red blood cells by haemoglobin.
Nutrients & Nitrogenous Wastes As the blood flows through capillaries surrounding the digestive system it picks up increased quantities of sugars, amino acids, salts, water, vitamins, etc that have been absorbed from the gut. (However, lipids are first absorbed into the lymphatic “drains” and enter the blood much later)
Carbon Dioxide CO2 is partly carried by the haemoglobin in red blood cells, but most of it is carried in the blood plasma, in the form of bicarbonate ions (HCO3-) You will have carried out an experiment to see the effect of dissolved CO2 on the pH of water.
This blood from the gut is collected in a vein which takes it directly to the liver. Here some of the nutrients may be absorbed from the blood for storage or chemical processing (e.g. glucose is extracted from the blood and polymerized to form glycogen and stored in the liver). Also in the liver, large amounts of the nitrogenous waste urea is added to the blood to be carried away and later excreted.
You might have chemically produced some CO2 and bubbled it through water. Using a pH meter, or perhaps Universal Indicator, you will have measured any change in the pH of the water. You would have found that the pH went down... i.e. the water became more acidic.
Later, as blood flows through capillaries in body tissues such as muscle or bone, nutrients are absorbed from the blood into the cells which need energy (glucose) and new chemical building blocks (amino acids, lipids).
Explanation and Chemistry: Carbon dioxide reacts with water to form carbonic acid CO2 + H2O
Sooner or later, every bit of blood flows through the kidneys which extract the nitrogenous wastes and excess salts and water for excretion as urine.
H2CO3
Carbonic acid is a weak acid which partly ionizes H+
H2CO3 Hydrogen ion makes water more acidic
+
CHANGES IN NUTRIENTS, WATER & WASTES AS THE BLOOD CIRCULATES
HCO3-
Lungs Bicarbonate ion. This is how CO2 is carried in blood
Water is carried as the liquid solvent of blood plasma.
Heart Some Nutrients to storage
Veins
Salts & Products of Digestion such as sugars and amino acids, are generally water soluble and are carried dissolved in the blood plasma. Lipids (Fats) absorbed from the digestive system are “packaged” in a protein coat which makes the fat molecule miscible in water. This means that, while not fully dissolved, the molecules can be dispersed in water and carried without joining together into droplets of fat and separating from the water.
Wastes into blood
Liver
Arteries
keep it simple science
Digested Nutrients into blood
Gut Wastes and excess water, salts excreted in urine
In this form they are carried dispersed in the blood plasma. Kidneys
Nitrogenous Wastes such as urea, are water soluble and carried dissolved in the blood plasma.
Nutrients from blood to cells
Body tissues HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
13
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Respiratory Gases O2 & CO2 As blood passes through capillaries in body tissues, oxygen is released from the haemoglobin molecules and diffuses along the concentration gradient into the body cells.
The Need to Remove Carbon Dioxide As already discussed, carbon dioxide doesn’t just dissolve in water, it reacts to form a weak acid. CO2 + H2O
There is always a concentration gradient favouring this because the cells are constantly using up oxygen for cellular respiration.
carbonic acid
Revision C6H12O6 + 6O2
Meanwhile, the concentration of carbon dioxide is high because of its constant production by cellular respiration, so it diffuses from the cells into the blood.
The Importance of Haemoglobin Blood is red because of the many red cells, and red cells are red because they are packed with the red-coloured, ironcontaining protein haemoglobin.
CO2
In the lungs, where the oxygen concentration is very high, some oxygen dissolves in the moisture lining the alveoli then diffuses into the blood flowing in the surrounding capillaries.
Carbon dioxide Lungs
Oxygen
Air
Blood
Oxygen is not very soluble in water, however, and if that’s all there was to the story, then our blood could never carry enough oxygen to supply our cells with what they need. Haemoglobin molecules have a great attraction for oxygen molecules and quickly pick up 4 O2 molecules each. Because of this, our blood can carry thousands of times more oxygen than would be possible by simply dissolving oxygen in the blood plasma.
CHANGES IN OXYGEN AND CARBON DIOXIDE AS THE BLOOD CIRCULATES
Arteries
Heart
Hb
Veins
Air
Blood
bicarbonate ion
To avoid this problem, CO2 is carried away by the blood as rapidly as it is produced in the cells.
When the blood gets to the lungs the opposite occurs. Inside the alveoli (air sacs of the lungs) the air has a very high concentration of oxygen and is very low in CO2. Therefore, oxygen diffuses into the blood, while carbon dioxide diffuses from the blood into the air. O2
HCO3-
At the concentrations produced by a typical cell, the hydrogen ions could easily lower the pH of the cytoplasm by 0.5 pH unit or more. Remember that enzymes are very sensitive to pH changes and quickly change shape and lose their catalytic activity. This would be disastrous for cell metabolism.
the important product. ATP is the energy supplier in cells
Chemical wastes
hydrogen ion
+
It’s the hydrogen ions that create problems. Hydrogen ions are acids and can lower the pH of cell cytoplasm.
6CO2 + 6H2O + ATP
Glucose and Oxygen delivered to cells by the blood stream
H+
H2CO3
+
O2
HbO2
abbreviation for Haemoglobin
“Oxyhaemoglobin”
When the blood gets to the body tissues with its load of oxygen, something very “clever” happens... The high concentration of dissolved CO2 lowers the pH of the blood slightly. This causes the haemoglobin proteins to change shape slightly and release the oxygen molecules. HbO2
Body tissues
Oxygen Blood Cells
keep it simple science
O2
Of course, this isn’t really “clever” in any sense of intelligence among haemoglobin molecules. It is the result of Natural Selection and Evolution... it gave a huge survival advantage to some primitive ancestor millions of years ago, so all mammals (and many others) have inherited this quite amazing substance.
CO2
This gas exchange and transport is essential for delivering oxygen to every cell for cellular respiration... ... but why must CO2 be removed? HSC Biology Topic 1 copyright © 2005-2007
+
The oxygen diffuses into the cells, and the freed haemoglobin molecules can pick up some of the CO2 molecules and carry them back to the lungs.
Carbon dioxide Cells Blood O2
Hb
14
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Oxygen Saturation & Its Measurement
Products of Blood Donation
The concentration of O2 and CO2 in the blood is of great interest to doctors monitoring a patient, or an athlete in training, or even to a pilot or mountain-climber at high altitude.
The Australian Red Cross Blood Service collects about a million blood donations per year. Most of this blood is used for people who need regular treatment with blood products for conditions such as leukemia.
The most important measurement is “percentage oxygen saturation” (%SpO2). A reading of 100 would mean that 100% of all haemoglobin in an artery is totally saturated with oxygen. Readings between 95-100% indicate good health, fitness and adequate oxygen supplies.
Only a very small amount is kept as whole blood for emergency transfusions. Most donated blood is separated into about 20 different fractions or products, so each donation can treat many different patients.
Lower readings (e.g. 80%) could indicate: • respiratory or circulatory problems in a patient • lack of fitness, or excessive exertion in an athlete • need for supplementary oxygen for a pilot or climber.
The main blood products are: Red Cell Concentrate which contains about twice as many red cells as normal, is used to boost the oxygencarrying capacity of patients with anaemia or after blood loss.
In years gone by, %SpO2 was measured by taking blood samples and carrying out complex chemical testing. With modern technology, however, the readings are done instantly and non-invasively by a small, portable instrument clipped onto the end of the finger or ear lobe.
Platelet Concentrate is given to patients who need extra blood-clotting capability, such as leukemia sufferers, or following severe blood loss.
Finger-c clamp Oximeter measures %SpO2
White Cell Concentrate is given to patients needing a boost to their immune system, perhaps following a severe infection.
Light source sends red light and infra-red
Plasma is the liquid part of the blood and is often given in emergency to boost the volume of blood following severe blood loss. Cryoprecipitate is a fraction collected from plasma and contains blood-clotting factors. It is used to treat severe haemorrhaging.
Receiver measures absorption of light by haemoglobin
Factor VIII and Monofix are extracts from plasma used to treat people who have haemophilia... an inherited, incurable disorder in which the blood will not clot properly. These blood products allow patients to lead a relatively normal life.
The “Oximeter” works by sending red light and infra-red beams through the flesh. The amount of each light absorbed by the haemoglobin gives a direct measurement of %SpO2, because haemoglobin carrying oxygen, or without, or with carbon dioxide, all absorb these light beams differently.
Perfluorocarbon-Based Substitutes Another area of research aims to develop a truly artificial blood Haemoglobin-B Based Oxygen Carriers are one of the areas of current research. substitute. The most promising base chemicals are the “perfluorocarbon” Haemoglobin extracted from animal blood compounds. can be purified and treated so that it is disease-free and cannot cause any allergic These can carry up to 5 times more or “rejection” responses in patients. oxygen than blood can, can be stored indefinitely at room temperature. The products can be stored for years at They can be made totally sterile and room temperature, and is highly effective at carrying oxygen and releasing it into the disease free.
ARTIFICIAL BLOOD?
Why Is It Needed? • Fresh blood cannot be stored for long, and many parts of the world lack the necessary storage facilities. • Many blood products can set off immune-responses in long-term patients, even after correct bloodtyping. (Similar to “rejection” of a transplanted organ)
tissues.
At least 5 different products are being
• Donated blood can carry Currently undergoing clinical trials, but not tested and trialled (USA), but none diseases, such as hepatitis or HIV. yet approved for medical use.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
15
are yet approved for medical use.
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Transport Systems in Plants
Active & Passive Transport
Note that the flow of water in the xylem costs the plant nothing in energy to run the system... it is “passive” transport.
In Preliminary Topic 2 you were introduced to the transport systems in plants... Xylem Tubes Carry Water
In contrast, the other transport system in plants is an “active transport” system... the plant must constantly supply energy to make it happen.
Hollow, dead cells, joined end to-end forming a tube
Phloem Tubes Carry Food Nutrients
While the xylem tubes are formed from dead cells, the phloem are living cells joined end-to-end. The ends of each cell are perforated (“sieve plates”) so each cell is open into the next so they form a continuous tube. PHLOEM CELL
alive and filled with cytoplasm.
Cell walls re-inforced with rings and spirals of lignin
Circulation of cytoplasm carries sugars through each cell
sugars actively transported in the cytoplasm of the cells
Sieve plate between cells
Xylem tubes are dead, hollow cells, joined end-to-end forming a continuous tube from root to leaf. The xylem tubes transport water (and dissolved minerals). How do they work to lift water from roots to leaves, against the force of gravity?
sugars diffuse from one cell into the next
“Companion cell”
has many mitochondria to provide ATP to the phloem cell
“Transpiration” is the evaporation of water from the leaves. When the stomates are open, water can constantly evaporate, creating a tension, or “pull” in the remaining water in the leaves.
While the xylem is a one-way flow system, the phloem system can carry food (especially sugars) in either direction. If a lot of photosynthesis is occurring, the phloem will carry sugar to storage sites in roots or stem. If photosynthesis is not possible for an extended time, then the phloem will carry sugars back from the storage sites to feed the leaf cells, or supply a growing flower or fruit.
Water molecules are quite strongly attracted to each other and tend to cling tightly together. This force is called “cohesion” and is the reason that water tends to form droplets... little blobs of water that cling together. So, when water evaporates from leaves and creates a “pull” force, each water molecule pulls on those behind it because of the cohesion. Each molecule pulls others upward and so the entire column of water in a xylem tube moves upwards to replace the water lost by transpiration. So water is pulled upwards by a combination of transpiration and cohesion. This flow is called the “transpiration stream”.
LO TU BE S
n
tio
ca slo
Sugar is removed by active transport, requiring energy. Water flows out due to osmosis, lowering pressure
16
how it works
EM
an Tr
Sugar solution flows due to pressure differential
In very narrow tubes (“capillaries”) the water will climb upwards against gravity because of adhesion, and drag more molecules along by cohesion. This happens in xylem and helps lift water upwards. keep it simple science
Translocation...
PH
Another factor which helps the process is called “capillarity” or the “capillary effect”. This is the way that water can “climb up” the walls of a container forming a meniscus in a test tube, for example. This happens because water molecules are not only attracted to each other (“cohesion”) but also to some other substances such as glass. This attraction is called “adhesion”.
HSC Biology Topic 1 copyright © 2005-2007
Sugar is carried in by active transport, requiring energy. Water flows in due to osmosis, raising pressure
Higher Pressure
DESTINATION Lower Pressure
www.keepitsimplescience.com.au
keep it simple science
Worksheet 3 Part A
TM
Baulkham Hills High School SL#802445
Part C Fill in the blanks Check your answers at the back.
WHEN COMPLETED,
Fill in the blanks
WORKSHEETS BECOME SECTION
Oxygen is carried by the a)...............-coloured, b)...................containing protein called c)......................................................... It has a great affinity for oxygen molecules, and each molecule can absorb d).................... (number) oxygen molecules, in which form it is called e)............................................................ In the body tissues, the presence of f)......................................... gas lowers the pH slightly, which causes haemoglobin to change shape slightly and g).......................................... the oxygen, which then h)..................................... into the cells.
SUMMARIES
Blood is made up mainly of a liquid called a).......................... and many blood cells. The most numerous blood cells are the b)........................... which contain the protein c)............................. responsible for carrying d).............................. gas. Most of the carbon dioxide in blood is carried in the form of e).................................... ions. These are made when carbon dioxide reacts with f).................. forming g).......................... acid. Most other substances carried in blood are dissolved in the h)....................................... This includes nutrients such as i).................................... and j)......................................., water and salts, and the nitrogenous waste k)............................. Lipids (fats) are first wrapped in a coating of l)............................ so they can be dispersed without separating.
The “%SpO2” is a measure of the i)............................................. in a person’s blood. Good health, fitness and adequate oxygen supply are indicated by readings above j)..............% This can be easily measured by a k).............................................. which sends beams of l).......................................... and ............................................. through a finger or ear-lobe. Oxygen saturation is measured according to how much of each type of light is m)....................................... by the blood. Most blood donated to the “Blood Bank” is separated into different fractions for different uses. Some of the main blood products are: • n)..................... Cell Concentrate, to boost O2-carrying capacity. •White Cell Concentrate, to boost o)............................................... p).................................. Concentrate, to help blood clotting q)...................................., which is the liquid part of the blood, used in emergency to increase r).....................................................
There are 3 types of blood vessels: the m)................................... have thick muscular walls to withstand the high n)...................... of the blood being pumped from the o).................................. p)................................ have thinner walls, and have q)................... along their length to prevent blood r)............................................ Capillaries have walls which are s)..........................................thick and form a network throughout the body’s t).............................. As the blood flows around the intestines it picks up u)......................................... It then flows straight to the v)...................................., where some nutrients are removed for w).......................&............................, and wastes such as x).............................are added. These wastes are later removed from the blood by the y)............................ and excreted with any excess z)........................... & .......................... as urine.
Research is going on into developing artificial blood. This is needed because fresh blood cannot be s)..................................... for long, and can cause t)............................................................. in some patients, and there is a danger that donated blood might carry u)..................................................... Two of the areas of research for artificial blood are v)................................-Based w)................................. Carriers, made from animal blood, and completely artificial substitutes based on the chemicals called x)......................................................
Meanwhile, when blood flows through the capillaries of the lungs, aa)........................... gas is absorbed into the blood and ab).............................. gas is released from blood into lungs. When blood flows through the body tissues, nutrients move from ac)............................ to ad)................................. as does ae)............................... gas, while af)..................................... gas moves the other way. Part B Questions 1. Write 2 chemical equations to summarize how carbon dioxide reacts with water. In what form is CO2 carried in blood?
Part D Transport in plants is carried out by 2 separate systems. The a)..................................... tubes carry water and dissolved minerals from the b)............................. to c)............................... These tubes are d).............................. (dead or living) cells. The transport is e)......................................... (active or passive) and the movement of water is called f)................................................. Basically the process works because, as water g)......................................... from the leaves, this “pulls” water up from above because water molecules are h)............................. and tend to cling together.
2. With reference to a chemical equation, explain why it is essential to remove carbon dioxide from body tissues.
Meanwhile, the i)..................................... vessels carry out j)................................................. (name of process) which moves k)................................................ around the plant to wherever it is needed. The cells are l)..................................... (dead or living) and the transport is m).........................................(active/passive) requiring the plant to n)......................................................... in order to make the process happen.
3. With reference to a chemical equation, explain how transfere of oxygen from blood to cells is facilitated.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
17
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
4. EXCRETION & WATER BALANCE The Importance of Water
Kidneys Also Excrete Metabolic Wastes
Life cannot exist without water. All living cells are about 75% water. The functions of water in living things include:
What Are the Metabolic Wastes? The many chemical reactions of metabolism sometimes produce chemicals which are toxic to cells, often because the chemical, when dissolved in water, can change the pH and reduce enzyme activity.
Water is the solvent of life All the chemical reactions of metabolism take place in water solution, and the transport of materials in cytoplasm, blood or phloem takes place mainly in water solution.
Therefore, it is essential that these wastes are removed (“excreted”) as soon as possible. The major wastes are:
Water is involved in life chemistry Water is a reactant or product of many metabolic reactions. The reactions of photosynthesis and cellular respiration are just two of the many examples.
• Carbon dioxide, produced by cellular respiration. As covered previously, it will lower the pH (acidic). It is carried in the blood and excreted by the lungs.
Water is vital in temperature regulation Water has a very high specific heat capacity. This means it can absorb (or lose) relatively large quantities of energy with minimal temperature change. This helps stabilize the temperature of all living things.
• Nitrogenous wastes, (contain nitrogen) are produced mainly from the metabolism of proteins. There are 3 main compounds that can be produced: • Ammonia in fish and aquatic invertebrates • Uric acid in birds, reptiles and insects • Urea in mammals and amphibians
Water also has a very high heat of vaporization. This means that when it evaporates it absorbs huge amounts of heat. This is why evaporation of perspiration from the skin has such a cooling effect.
Excretion & Water Balance in Fish Fish produce the waste ammonia which is very alkaline and toxic. Luckily it is very soluble in water. Since they live surrounded by water, fish simply excrete ammonia from their gills by simple diffusion.
Water supports and cushions cells and organs Many plants and animals rely on water for body support. Non-woody plants pump their cell vacuoles full of water to make cells “tight” and keep stems and leaves upright. Animals such as worms rely on the hydraulic pressure of water in their tissues to support their body and maintain its shape.
Their kidneys are used not so much for excretion, but for maintaining their water balance. Freshwater fish and saltwater fish have opposite problems with water balance. SALTWATER FISH
In vertebrate animals the water solutions in the tissues helps to cushion organs against bumps and impacts. (eg cerebrospinal fluid around the brain)
sis
Constantly drink to replace water (but get salt, too)
Homeostasis of Water & Salts It’s not just the water that is important, but its concentration, and the concentration of substances dissolved in it, such as salts.
Gills excrete Ammonia, Carbon Dioxide and excess salt
If the concentrations are not kept at the correct levels, then osmosis may cause problems. Cells could lose water and dehydrate, or gain too much water and be damaged.
FRESHWATER FISH
THE CONCENTRATION OF WATER & DISSOLVED SALTS MUST BE MAINTAINED THIS IS ANOTHER EXAMPLE OF HOMEOSTASIS
keep it simple science
Kidneys produce small amounts of urine to save water
Tiss u (mai es gain nly t w hrou ater by gh g o ills) smosis
Do not drink
IN MOST ANIMALS WATER BALANCE IS REGULATED BY THE KIDNEYS HSC Biology Topic 1 copyright © 2005-2007
Wat (ma er loss inly f thro rom ti ugh ssue sb gill yo s) smo
Kidneys produce a lot of dilute urine to remove water from body
18
Gills excrete Ammonia & Carbon Dioxide, and actively absorb salts
www.keepitsimplescience.com.au
TM
keep it simple science
Baulkham Hills High School SL#802445
Excretion in Terrestrial Environments
How the Kidneys Work in Mammals
The fish can get away with production of highly toxic ammonia. They can rely on constant diffusion of ammonia from the blood in their gills into the water environment which surrounds them.
Each kidney contains about 1 million nephrons. Each nephron is a complicated tangle of blood vessels and renal tubules (=small tubes), but what happens in a nephron can be summarized in a very simple way... K.I.S.S.
In terrestrial environments, waste gases can do exactly the same; that’s how carbon dioxide is excreted... by simple diffusion from the blood to the air in the lungs. However, nitrogenous wastes are not gaseous and need to be excreted in water solution. This means that:
Filtration removes some of the water and many small dissolved molecules (including the waste urea) from the blood into the renal tubules. This occurs because the walls of the glomerulus are “leaky” and the blood is under high pressure.
• nitrogenous wastes are produced not as ammonia, but the less toxic compounds urea (mammals) or uric acid (birds, reptiles, insects)
Reabsorption then occurs to move useful substances back into the blood. This is achieved by: •Active Transport of sugar, amino acids & salts from the renal tubules back into the blood. This requires energy to be used to transport these chemicals across the cell membranes, against a concentration gradient. •Osmosis then occurs, which causes water to flow from the tubules back into the blood. This is Passive Transport and costs the body no energy.
• excretion is via the kidneys, and the simple processes of diffusion and osmosis are not adequate to achieve this. For simple diffusion to achieve excretion it would require huge amounts of water to be excreted too, and no terrestrial animal can afford to do this, especially in a desert.
Renal Tubules Glomerulus
THE NEPHRON of the KIDNEY
a coiled blood vessel Blood in from artery This blood contains urea
Filttrattion n occurrs herre Bowman’s Capsule
Reabsorrpttion n occurrs herre
a “receiving cup” to collect the filtrate liquid from the blood
Urine flows to collecting duct Blood Capillary Network
shown in simplified form
Blood out
then via Ureter to Bladder, for excretion
to vein This blood has had wastes removed, and water balance adjusted for Homeostasis
Filtration is the process in which some water and
Reabsorption is the process in which any useful substances (such as sugars & amino acids) are absorbed back into the blood. Water & salts are also reabsorbed, but in varying quantities... the body is adjusting water balance for Homeostasis
many dissolved substances (including sugar, salts & urea, BUT NOT any cells or blood proteins) leave the blood and flow into the renal tubules.
Urea is not reabsorbed back into the blood. Urea and some water continue along the tubule. This liquid is URINE. Urine flows into the Ureter and is carried to the Bladder for storage. When the bladder becomes full, the urine is excreted via the Urethra. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
19
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
The Kidneys & Homeostasis The kidneys are not just used for excretion. As well, the kidneys can adjust the “water balance” of the body by allowing more, or less, urine to be produced. In this way the kidneys are a vital part of homeostasis. Once again, the Hypothalamus is involved, but the control mechanism is by hormones... chemicals which are released into the blood and exert a control function on some “target organ”. In this case the hormone is called “Anti-Diuretic Hormone” (ADH) and the target organ is the kidney, specifically the nephron tubules. Pituitary Gland releases more ADH (Also nerve signals to brain cause “thirsty” feeling so you will want to drink)
BODY RETAINS MORE WATER, excretes less urine. Urine is more concentrated
Note the typical pattern of a negative feedback system
to Pituitary Gland
Nerve Command
ADH causes more reabsorption of water from kidney tubules
WATER LEVEL IN BODY TOO LOW
WATER LEVEL IN BODY TOO HIGH
BODY PASSES MORE WATER, excretes more urine. Urine is more dilute.
Less ADH causes less reabsorption of water from kidney tubules.
The effect of ADH is to alter the permeability of the membranes lining the tubules of the kidney nephrons. Increased ADH levels make the membranes more permeable to water, so more water is reabsorbed back into the blood. This means that less urine is produced.
If salt levels are too low, special cells in the adrenal glands detect this and increase the production of aldosterone into the bloodstream. This causes the cells lining the nephron tubules to actively transport more sodium ions back into the blood. Chloride ions follow the sodium, and so more salt is reabsorbed.
If the body is over-hydrated, the production of ADH is reduced. This causes the tubules to become less permeable to water so less is reabsorbed into the blood. The result is more urine being produced.
If salt levels are too high, the adrenal glands produce less aldosterone so less salt is reabsorbed, and the excess salt will be excreted in the urine.
ADH is the hormone controlling the water levels, but this is only part of the “osmotic balance” story... the salt levels can be controlled too. Read on...
keep it simple science
Pituitary Gland releases less ADH (Also nerve signals to brain cause feeling that you do NOT want to drink)
Control of Salt Levels by Aldosterone Sitting on top of the kidneys are the “Adrenal Glands” which produce a variety of steroid hormones controlling a number of body functions. One of the adrenal hormones is Aldosterone which controls reabsorption of salt from the nephron tubules.
How the Hormones Work The hypothalamus monitors the blood flowing through it for the “osmotic balance” of water and dissolved salt. If the body is even slightly dehydrated, more ADH is released by the pituitary gland and circulates in the blood stream.
HSC Biology Topic 1 copyright © 2005-2007
Nerve Commands
HYPOTHALAMUS & PITUITARY GLAND
Between ADH and aldosterone the body maintains a constant “osmotic balance” of water and dissolved salt... Homeostasis.
20
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Kidney Structure & Nephrons
Addison’s Disease & HRT Addison’s Disease occurs when a person’s adrenal glands do not produce enough aldosterone, even when their salt levels are too low. Their nephrons constantly fail to reabsorb salt and so the “osmotic balance” of the body is chronically out of order.
You may have dissected a kidney in your laboratory work in class. You should be able to relate the gross structure of the kidney and urinary system to the structure and functioning of the nephrons. This is summarized by these diagrams.
This leads to a variety of problems and malfunctions throughout the body involving the heart, intestines and liver, and may cause psychological disorders as well.
DISSECTED KIDNEY
This is a disease that can be sucessfuly treated by “Hormone Replacement Therapy” (HRT).
Position of an Adrenal Gland (not usually present in school specimens)
Renal Cortex
Dark red in colour due to the many blood capillaries of the nephrons
Artery & Vein
A person with Addison’s Disease can be treated with appropriate doses of steroid hormones (usually cortisone) and although they cannot be totally cured, they can lead a normal, symptom-free life on HRT.
Medulla
Lighter in colour... less blood vessels. Here many collecting ducts carry urine to the ureter
Renal Dialysis If a person’s kidneys cease functioning properly he/she can no longer remove toxic wastes such as urea from the blood, nor maintain homeostasis of “water balance”. In the case of complete kidney failure, this condition is fatal within about 3 days without treatment.
Ureter
carries urine to bladder
GENERAL STRUCTURE OF THE URINARY SYSTEM
Over the past 40 years or so, many people have been successfully treated by receiving a kidney transplant. However, they may have to wait months or years to find a suitable organ donor. In the meanwhile, they need to be treated by Renal Dialysis... the use of medical technology to remove wastes from the blood artificially. In effect, a renal dialysis machine is an “artificial kidney”.
Kidneys
Ureters
The simplified diagram explains how this works. Blood returns to patient’s vein
FLUID IN
wastes such as urea diffuse
Patient’s blood from an artery
out of the blood
Bladder Urethra
Dialysis fluid flows past the tubes carrying the blood
Comparison of Renal Dialysis with Natural Kidney Function Similarities •Both processes remove urea and other wastes from the blood. •Both rely on movement of dissolved substances through semi-permeable membranes.
OUT
Pump Blood flows through “dialysis tube” with semi-permeable membrane walls
Differences • Kidney function involves the 2 steps of filtration and reabsorption; dialysis involves only 1 step of diffusion of wastes from blood. • In a kidney, movement across membranes is achieved by both active transport and by passive osmosis and diffusion; dialysis involves only passive diffusion.
The dialysis fluid contains water, salts, sugars, minerals etc exactly as in healthy blood plasma. Since there is no concentration gradient for these chemicals they do not diffuse in or out of the blood. However, the wastes such as urea are in higher concentration in the blood, and so they diffuse from the blood into the dialysis liquid, which is later disposed of. HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
21
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Water Balance in Australian Animals
Water Conservation & Excretion in Australian Mammals
The different conditions of each environment dictate what an animal must do to to achieve homeostasis of its “water balance”. In each environment there are different problems to be overcome, and the animal’s body organs must respond appropriately. Exactly how homeostasis is achieved will be reflected in the urine the animal produces. Comparison of Urine Production in Different Environments Marine Fish (revise page 18) • problem: constant loss of water by osmosis. • urine: small amount, to conserve water. Urine does not contain wastes, since ammonia is excreted from the gills. Freshwater Fish (revise page 18) • problem: constant gain of water by osmosis. • urine: large volume, to remove water. Urine does not contain wastes, since ammonia is excreted from the gills. Terrestrial Mammal • problem: must excrete wastes in urine, but cannot afford to lose too much water, especially in dry Australian ecosystems. • urine: generally small volume, to conserve water. Urine is relatively highly concentrated in wastes such as urea.
Many Australian environments are desert or semi-arid and water conservation is vital for survival. Some adaptations for temperature control, while conserving water, were covered earlier in this topic (see page 10). Many Australian mammals have excretory systems that also contribute to water conservation, while managing to efficiently remove their nitrogenous waste, urea. Photo by Diana
The desert-living Red Kangaroo, the Spinifex Hopping Mouse, and even the Koala (which rarely drinks) all have the ability to produce very small amounts of highly concentrated urine. They achieve this by: • having longer tubules in their kidney nephrons, which allows for more reabsorption of water back into the blood, thus less urine is produced. • the cells lining the tubules are able to actively transport urea from blood into the urine. So, not only is urea not reabsorbed from the “filtrate” liquid, but is actively “pumped” from the blood.
Water Conservation & Excretion in Insects All insects are small, and most are adapted for flight. This means they cannot afford to carry large amounts of water in their bodies just for the purpose of excreting urine. Their excretory system must be able to remove nitrogenous wastes, while losing only a minimum of water. Firstly, their nitrogenous wastes are processed chemically into the form of uric acid, which has a low solubility in water. This means that, when their urine is separated from the blood (filtration) and then concentrated by reabsorption of water, the uric acid precipitates as a solid.
The result is less water and more urea in their urine.
Enantiostasis Enantiostasis is a special case of homeostasis. It refers to the maintenence of metabolic and physiological functions, (i.e. homeostasis) despite significant variations in the surrounding environment.
After further reabsorption of water, the insect’s urine is a semi-solid paste, which is passed into the rectum and excreted with their solid digestive wastes. The Malpighian Tubes are the insect equivalent of kidneys
An important example is an estuary, where river meets sea. Organisms are able to maintain their water and salt balance, despite wild fluctuations in the water and salt concentrations around them, every time the tides change.
Intestine
Some of the ways they cope with this are:
ANUS
• burrowing into the mud, where the salt concentrations are more stable (e.g. crabs, yabbies) • closing their shell, to avoid extreme conditions they cannot cope with. (e.g. oysters) • switching their excretory systems from water conservers when salty, to water excreters when fresh. (e.g. fish)
MOUTH MALPIGHIAN TUBES extend through insect’s body, collecting and concentrating urine. Urine is emptied into the gut for excretion.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
22
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Water Conservation in Australian Plants
How Plants Cope With Salt
The characteristics of Australia’s sclerophyll plants were dealt with in the Preliminary Course topic “Evolution of Australian Biota”.
Many of the Australian coastal estuaries are home to Mangrove trees which have a number of adaptations to cope with the salt water that covers their roots with every high tide.
In summary, the sclerophyll plants include the gum trees, banksias and acacias (wattles) and all show numerous adaptations to conserve water in our arid climate, such as:
To maintain their “osmotic balance” they must both conserve water and deal with high levels of salt. One of the most common species is the “Grey Mangrove”, Avicennia marina, which has all the following adaptations:
Small & narrow to reduce Surface Area for less evaporation GUM LEAVES
• leaves with a thick, waxy cuticle and fine hairs on the undersurface, all to minimize water loss. • salt glands in the leaves which excrete a concentrated salt brine onto the leaf surface. The salt gets washed away when it rains. • salt is deposited in older leaves, so when they drop off they carry a load of excess salt away.
Thick, waxy cuticle minimizes evaporation
• special tissues within their roots which allows water to pass through, but reduces the passage of salt. This helps to reduce the salt intake.
Droop downwards to avoid the heat of midday for less evaporation
Mangroves coastal NSW
• small, narrow, drooping leaves with thick, waxy cuticles • In dry times, gum trees shed many of their leaves so that there are less surfaces for evaporation. In some species, such as the River Red Gum, entire branches are sacrificed by cutting off their water supply so that they die. (This is why gum trees are dangerous... whole dead branches often fall off onto cars, homes or campsites.) • Species such as Spinifex grass limit evaporation by having fine hairs all over their leaves. This traps a layer of air near the leaf so that wind cannot increase evaporation rates. • Generally, all Australian sclerophylls have fewer stomates on their leaves to limit the water loss from transpiration.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
23
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
So, an increase in ADH secretion leads to greater al)................................. (excretion/retention) of water, while a decrease in ADH results in am).......................... (more/less) urine production.
Worksheet 4 Fill in the blanks Check your answers at the back. Water is vital to all living things because: 1. It is the a)................................... of life, and most substances are b).............................. in water solution. 2. Water is involved in many c)............................... reactions, such as photosynthesis or d)............................................. 3. Water has very high “heat e)....................................” and “heat of f)....................................” so it is vital to temperature control 4. Water g)................................ and cushions cells and organs. For example, plants rely on water in cell h).................................. to keep leaves and stems upright. Maintaining the correct balance of both water and dissolved i)................................ is another aspect of j)......................................
Another hormone called an)....................................... is produced by the ao).......................................... glands controls the reabsorption of ap).................................. Some people do not produce enough of this hormone and so have a chronic salt-balance problem called aq)................................. Disease. This disease is treated by ar)................................................... Therapy (HRT). If a person’s kidneys fail, they can have their blood “cleaned” of wastes by the process of “Renal as)..................................... This is similar to kidney function in that both involve movement of dissolved chemicals through at)............................................... membranes. It is different from kidney function in that it involves only au)............ (number) process, which involves av).............................. (active/passive) diffusion. Kidney function has aw).................... (number) steps, and involves both ax).............................. (active/passive) transport and osmosis.
In vertebrate animals, the control of water balance is done by the k)..............................., which also are responsible for excretion of l).................................. wastes. Different animals produce different wastes: the fish produce mainly m)...................................... while birds and insects produce n)................................................... and mammals produce o).................................. In fish, the kidneys are used mainly for p).......................................... because excretion of the ammonia takes place from their q)................................
Insects process their nitrogenous wastes into the chemical ay)......................................... which has very low solubility. This allows them to excrete “urine” which is almost entirely az)........................... Many Australian mammals excrete very ba)................................ (small/large) amounts of bb)................................... (dilute/concentrated) urine. They achieve this by having increased ability to reabsorb bc)............................... from the nephron tubules, and can bd).................................... (actively/passively) pump urea from be)............................. into the bf)...................................
Each kidney contains about 1 million units called r)................................ There is a coiled blood vessel, the s)..................................... which is inside the t).............................. capsule. Here the process of u).............................................. takes place, where water and many dissolved substances leave the blood and flow throught the v).............................................. The second process is w)......................................... in which any useful substances (most of the water, plus x)............................... and ..................................) are absorbed back into the y)...................................... by a combination of active transport and z)..................................... Some water plus the aa).............................. are not reabsorbed but pass into a ab)..................................... duct, and down the ac)..................................... to the bladder to await excretion. The kidneys also have a role in ad).......................................... by adjusting the amounts of water and ae)......................................... that are reabsorbed into the blood. This function is controlled by the af)................................. which monitors “water balance” and controls the release of the hormone ag).............................. from the ah)................................... gland. This hormone increases the permeability of membranes in the ai)...............................so that aj)............................. (more/less) water will be absorbed, and ak)............................ (more/less) urine formed. HSC Biology Topic 1 Copyright © 2005-2007
keep it simple science
When an organism can maintain homeostasis despite significant variations in the environment, this is called bg).......................................... A good example is the way that estuarine animals can maintain bh)...................................... balance despite the fluctuations in salt concentrations as the bi)......................... change. Mangrove plants deal with salt by special root tissue to bj).............................. its entry, or by bk).................................. salt onto their leaves, or by bl).......................... salt in older leaves which are later shed. Many Australian plants are well-adapted to conserve water by such features as leaves which are bm)............................................ (shape & size) and are covered with a thick, waxy bn)........................................... They often have fewer bo)......................................... on their leaves, or may be covered with bp)..................................... to trap a layer of air. WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES
24
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Blank “Mind Map” Use this scaffold to try and learn all the parts of this topic. Some students find that if they know what’s in the topic, they also remember the facts & concepts that need to be learnt.
MAINTAINING A BALANCE
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
25
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Practice Questions
5. The effect on enzyme activity of increasing the substrate concentration is best described as: A. Activity rises to an “optimum” level, then declines again. B. Activity always rises as substrate concentration increases. C. Activity declines as substrate concentration increases. D. Activity rises, then levels off as the enzyme becomes saturated.
These are not intended to be "HSC style" questions, but to challenge your basic knowledge and understanding of the topic, and remind you of what you NEED to know at the K.I.S.S. principle level. When you have confidently mastered this level, it is strongly recommended you work on questions from past exam papers.
Part A
6. Which of the following is least likely to be controlled by a negative feedback system? A. Body temperature B. Blood sugar levels C. Rate of digestion D. Water & salt levels.
Multiple Choice
1. Which of the following is NOT true about enzymes? Enzymes:A. are catalysts which speed up chemical reactions. B. are carbohydrate molecules of a special shape. C. will only work within a narrow range of temperature & pH. D. are substrate-specific; each only works for one substrate. The graph shows the rate of an enzyme-catalysed reaction. Questions 2 and 3 refer to it.
B
8. Which of the following is a response by an effector organ which would be appropriate when the body is too warm? A. Muscles begin shivering. B. Blood vessels dilated. C. Body hairs erected, forming “goose bumps”. D. Metabolic rate increased by the hormone thyroxine.
C Rate of reaction
2. Which part of this graph (A,B,C or D) corresponds to the enzyme having the best 3dimentional shape to fit its substrate?
7. The “control centre” for homeostasis involving the nerve system is the: A. Hypothalamus B. Cerebrum C. Cerebellum D. Pituitary gland
A
D Temperature
3. At point D on this graph, you could describe the enzyme as: A. saturated with substrate. B. optimum shape. C. decomposed. D. denatured.
9. Which statement is correct? A. Ectotherms such as fish, generate their own body heat. B. Endotherms such as birds, rely on their surroundings to supply their body heat. C. Ectotherms such as mammals, generate their own body heat. D. Ectotherms such as reptiles, rely on their surroundings to supply their body heat.
4. This graph compares the performance of 2 enzymes at different pH levels.
10. A typical response of an ectotherm to over-heating is: A. sweating B. sun-baking C. seeking shade D. shivering
Enzyme Q Enzyme P Enzyme Activity
11. An important adaptation in Australian mammals to help keep cool in a desert environment is: A. a lot of sweat glands in the skin. B. a “stocky”, thick-set shape to minimize heat absorption. C. large ears to acts as heat radiators. D. thick fur to prevent heat getting to their body.
1
2
3
4
5
6 pH
7
8
9
12. A blood vessel with relatively thin muscle layer and equipped with one-way valves is most likely a: A.Vein B. Arteriole C. Artery D. Capillary
10
It would be reasonable to conclude that: A. “P” is a stomach enzyme, “Q” is an intra-cellular enzyme. B. “P” is from a plant cell, “Q” is from a mammal cell. C. “Q” performs better than “P” under all conditions. D. Both would be at their optimum activity at about 40oC.
HSC Biology Topic 1 Copyright © 2005-2007
keep it simple science
13. As blood flows through a capillary in an active muscle, you would expect changes in the substances carried in the blood, as follows: A. Increase in CO2, decrease in O2 and sugars. B. Decrease in CO2 and sugars, increase in O2 C. Inrease in CO2 and sugars, decrease in O2 D. Decrease in CO2 and O2, decrease in sugars 26
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Part B
14. Which line correctly identifies the way in which most of the oxygen and carbon dioxide gases are carried in the blood? Oxygen Carbon Dioxide A. dissolved in plasma, in haemoglobin B. in haemoglobin, dissolved as bicarbonate ion C. in white cells, in haemoglobin D. in haemoglobin, dissolved as carbonic acid
21. (4 marks) Discuss the importance of shape to the characteristics of an enzyme, with specific reference to a) why each enzyme will usually only catalyse only one reaction.
15. The “Oximeter” is able to measure percentage oxygen saturation of the blood because, depending on the amount of oxygen present: A. the blood pH changes B. the ratio of red and white cells changes C. the blood flows at a different rate D. haemoglobin absorbs light differently
b) why enzymes only work within fairly narrow ranges of temperature and pH. 22. (8 marks) The following data was collected in an experiment in which the time taken for a chemical reaction catalyzed by an enzyme, was measured at different temperatures. Time taken for reaction (min.) Temp (oC) 5 4.0 10 2.0 15 1.0 20 0.2 25 2.5 30 10 a) Tabulate this data appropriately, adding a third column for “Reaction Rate” and calculating values for this.
16. Which statement about plant transport systems is correct? A. Xylem use active transport for Transpiration. B. Xylem cells are alive and carry out Translocation C. Phloem cells use active transport to move nutrients D. Phloem tubes carry out Transpiration by passive means 17. A freshwater fish: A. produces a large volume of dilute urine B. produces a small volume of concentrated urine C. excretes urea in large amounts via the kidneys D. excretes water from its gills and must drink to replace it
b) Construct a graph of Temperature v Rate. c) Is it likely that this is a human enzyme? Explain. 23. (5 marks) a) What is meant by “Homeostasis” b) What is the link between the necessity for homeostasis and enzymes? c) Using a simple example, explain the concept of “negative feedback” as a way to maintain stability of any system.
18. In the mammalian kidney nephrons the formation of urine occurs in 2 stages. Which line describes correctly the location of each process? Filtration Reabsorption A. Glomerulus Bowman’s capsule B. Renal tubules Ureter C. Glomerulus Renal tubules D. Bowman’s capsule Collecting duct
24. (8 marks) a) Discuss the role of the hypothalamus in the regulation of body temperature in a mammal.
19. An increase in the level of the hormone “ADH” would cause the kidney nephrons to: A. reabsorb less salt B. reabsorb more water C. reabsorb more salt D. reabsorb less water
b) Give an outline of how the blood vessels function as “effectors” in the regulation of body temperature. c) List 3 other effectors (apart from blood vessels) involved in temperature regulation. 25. (6 marks) a) Explain the difference between an ectotherm and an endotherm.
20. Insects conserve water by excreting their nitrogenous wastes in the form of: A. a semi-solid paste of uric acid B. a small volume of urine, highly concentrated in urea C. a large amount of ammonia-containing urine D. pellets of solid urea HSC Biology Topic 1 Copyright © 2005-2007
keep it simple science
Longer Response Questions
Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate.
b) Using a named Australian example, outline how an ectotherm regulates its body temperature. c) Using a named Australian example, outline 2 adaptations of desert-living endotherm to keep their bodies cool. 27
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445 32. (4 marks) Outline the processes of Filtration and Reabsorption in the nephron of a mammalian kidney. Identify where each process occurs and the main events occurring.
26. (3 marks) Describe some adaptations of sclerophyll plants which help them minimize absorption of heat from the Sun. 27. (5 marks) Describe the structural difference(s) of veins and arteries, and relate these differences to the functions of these blood vessels.
33. (6 marks) Compare and contrast the role of the hormones “ADH” and “Aldosterone” in the maintenence of mammal homeostasis. Your answer should include • source of each hormone • precise effect on the target organ • how this contributes to Homeostasis
28. (9 marks) a) Contrast the way(s) that the gases oxygen and carbon dioxide are carried in the blood.
34. (5 marks) a) Outline the process of excretion of nitrogenous wastes in insects, explaining how it contributes to conservation of water in their bodies.
b) These gases are described as the “respiratory gases” because of their involvement in cellular respiration. Summarize this process with a chemical equation. c) How is the release of oxygen from the bloodstream facilitated by the high concentration of carbon dioxide in the body tissues?
b) Using a named example of an Australian mammal, explain how the excretion of nitrogenous wastes is achieved with minimum water loss.
29. (4 marks) Identify 2 of the “blood products” extracted from donate blood, and describe the uses of these products.
35. (8 marks) a) What is “Enantiostasis”? Give an example of an environment where this process is vital and outline some of the strategies for achieving enantiostasis in the named environment.
30. (6 marks) Construct a table to contrast the processes of Transpiration and Translocation in plants. Your answer should cover: • the name and nature of the vessels involved • the substance(s) transported • the basic nature of the processes
b) Identify strategies for conservating water in 2 named Australian plants. c) Describe 2 strategies used by mangrove trees to maintain water balance in a saline environment.
31. (4 marks) Discuss briefly the importance of water in living organisms, identifying 4 functions of water.
Need to contact us?
keep it simple science
(02) 6583 4333
keep it simple science
FAX (02) 6583 9467
www.keepitsimplescience.com.au
[email protected]
TM
ABN 54 406 994 557
HSC Biology Topic 1 Copyright © 2005-2007
PO Box 2575 PORT MACQUARIE NSW 2444
28
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Answer Section
Worksheet 1 (continued)
Worksheet 1
Part C a) stable / at the same level c) pH e) blood sugar g) receptor i) effectors k) hypothalamus
Part A a) metabolism c) used up / consumed e) protein g) 3-dimensional shape i) specific l) shape o) 7 q) above 7 s) stomach
b) speeds up d)enzymes f) amino acids h) substrate(s) j) & k) temperature & pH m) & n) acidity & alkalinity p) below r) 7 / neutral t) acidic
Worksheet 2 a) hypothalamus b) effector c) dilation d) more e) sweat f) perspiration g) evaporates h) hormones i) thyroid j) constricted k) the skin l) raised / erected m) insulate n) shiver o) ectotherms p) reptiles q) Sun r) Blue-tongue lizard s) sunbakes t) seeks shade u) copperhead snake / corroboree frog v) becoming dormant w) endotherms x) & y) mammals & birds z) feathers aa) blubber (fat) ab) ears ac) lose water ad) fore arms ae) insulation af) shunted back into the body ag) deciduous ah) shed their leaves ai) stomates aj) needle / spine ak) light al) sclerophyll am) narrow an) droop downwards
Activity
Part B 1. graph 2.a) reaction rate (=activity) increases as temp. goes up because molecules are more likely to collide and react with each other.
Temp
b) Above the optimum the shape of the enzyme protein begins to change and be distorted. The substrate(s) no longer fit the enzyme perfectly, and activity declines rapidly.
Activity
3. graph 4. At the optimum pH the shape of the enzyme is a perfect “lock & key” shape to fit the substrate, so activity is at a maximum.
Worksheet 3 pH
Part A a) plasma c) haemoglobin e) bicarbonate g) carbonic i) sugars k) urea m) arteries o) heart q) valves s) one cell u) digested nutrients w) processing & storage y) kidneys aa) oxygen ac) blood ae) oxygen
5. At pH’s either side of optimum the shape of the enzyme changes so that the “fit” with the substrate is no longer perfect, so activity declines. 6. graph Activity
7. a) As the concentration of substrate molecules increases, it becomes more likely that they will collide with an enzyme and Substrate concentration undergo the reaction. So reaction rate increases. b) However, once all the available enzyme molecules are being used, (they are “saturated” with substrate) increasing the concentration cannot increase reaction rate any further, so the graph levels off.
HSC Biology Topic 1 copyright © 2005-2007
b) temperature d) water f) negative h) control centre j) nervous l) brain
keep it simple science
29
b) red d) oxygen f) water h) plasma j) amino acids l) protein n) pressure p) Veins r) flowing backwards t) tissues v) liver x) urea z) water & salts ab) carbon dioxide ad) cells af) carbon dioxide
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
Worksheet 4 (continued) ac) ureter ad) homeostasis ae) salt af) hypothalamus ag) ADH ah) pituitary ai) renal tubules aj) more ak) less al) retention am) more an) aldosterone ao) adrenal ap) salt aq) Addison’s ar) Hormone Replacement as) Dialysis at) semi-permeable au) one av) passive aw) two ax) active ay) uric acid az) solid / dry ba) small bb) concentrated bc) water bd) actively be) blood bf) tubules / urine bg) enantiostasis bh) water & salt bi) tides bj) limit bk) secreting / excreting bl) storing / accumulating bm) small & narrow bn) cuticle bo) stomates bp) hairs
Worksheet 3 Part B 1. Carbon dioxide reacts with water to form carbonic acid
CO2 + H2O H2CO3 Carbonic acid is a weak acid which partly ionizes H2CO3 H+ + HCO3Carbon dioxide is mostly carried as bicarbonate ion. 2. The equations show that carbon dioxide reacts with water forming an acid. If allowed to accumulate, this would lower the pH, which could seriously affect the activity of enzymes and disrupt metabolism. 3. As shown in the equations above, the presence of carbon dioxide lowers the pH. In tissue capillaries, the slightly lowered pH alters the shape of the haemoglobin molecules slightly. This causes them to release the oxygen molecules they are carrying, which then diffuse into the cells. Part C a) red b) iron c) haemoglobin d) 4 e) oxyhaemoglobin f) carbon dioxide g) release h) diffuse i) percent oxygen saturation j) 95% k) Oximeter l) red light & infra-red light m) absorbed n) Red o) immunity p) Platelet q) Plasma r) blood volume s) stored t) immune-responses u) diseases v) Haemoglobin w) Oxygen x) Perfluorocarbons Part D a) xylem c) leaves e) passive g) evaporates i) phloem k) nutrients / sugars m) active
Practice Questions Part A 1. B 2. B 3. D 4. A
HSC Biology Topic 1 copyright © 2005-2007
b) roots d) dead f) transpiration h) cohesive j) translocation l) alive n) use energy
17. A 18. C 19. B 20. A
21. a) Enzymes are protein molecules and each has a a particular 3dimensional shape which fits its substrate like a key fits a lock. Usually each enzyme will only “fit” one particular substrate, so it will only catalyse one reaction. b) Any change in temperature or pH can change the shape of an enzyme, by causing the protein chain to alter the way it is folded and twisted. As its shape changes, its ability to “fit” the substrate will change too. Thus each enzyme only works fully within relatively narrow ranges of temperature and pH.
b) dissolved d) metabolic / chemical f) vaporization h) vacuoles j) homeostasis l) nitrogenous n) uric acid p) water balance r) nephrons t) Bowman’s v) renal tubules x) sugars / salts / amino acids z) osmosis ab) collecting keep it simple science
13. A 14. B 15. D 16. C
Part B Longer Response In some cases there may be more than one correct answer possible. The following “model” answers are correct, but not necessarily perfect.
Worksheet 4 a) solvent c) chemical e) capacity g) supports i) salts k) kidneys m) ammonia o) urea q) gills s) glomerulus u) filtration w) reabsorption y) bloodstream aa) urea
Multiple Choice 5. D 9. D 6. C 10. C 7. A 11. C 8. B 12. A
22. a) Table should • be ruled • have clear headings The values in the 3rd column should be: Reaction Rate (min-1)
0.25 0.5 1.0 5.0 0.4 0.1 (These values are calulated as 1/time taken)
30
www.keepitsimplescience.com.au
keep it simple science
22. (continued) b)
Baulkham Hills High School SL#802445 25. a) Endotherms are animals which generate their own body heat. Ectotherms rely on their environment to supply their body heat; they do not generate internal body heat. b) Ectotherms such are the Blue-Tongue Lizard often use instinctive behaviours to regulate temperature. When too cold, it will sunbake, flattening its body to increase the surface area exposed to the Sun. When too hot, it will seek shade and avoid the heat of the Sun. c) Desert-living endotherms, such as the Bilby, cannot afford the water loss involved with sweating to cool off. Instead, they have large ears to radiate heat away. They seek shade in the heat of the day and are active only in the evenings and early morning. Instead of sweating, they “pant” so that evaporation from the mouth and throat has a cooling effect.
5
Reaction Rate v Temp. Graph
1
2
3
4
Reaction Rate (1/min)
c) No. The graph shows that at human body temp. (37C) the enzyme’s activity is almost zero. This enzyme would NOT function in a human body.
TM
0
5
10
15
20
Temperature
25
30
(oC)
23. a) Homeostasis is the process of maintaining a stable, internal environment, for such things as temperature, pH, water balance, etc. b) Homeostasis is vital so that the optimum conditions (of temp., pH etc) for enzymes to function efficiently are maintained. Efficient enzyme activity is essential so that the reactions of metabolism occur at a rate appropriate for life functions. c) example: thermostat control of an oven A temperature sensor constantly monitors the temp. If oven is too cool, the control mechanism sends an electrical signal to turn the heating element on. (effector) If the oven is too hot, a signal is sent to turn the heating element off, so the oven will cool down. By always taking action in the opposite direction (negative feedback) a relatively stable temperature is maintained.
26. Sclerophyll plants have • small, narrow leaves to reduce surface area exposed to Sun • shiny leaf cuticle to reflect some radiant heat • leaves which “droop” downwards. This allows for absorption of light for photosynthesis in the cool of the morning, but avoids heat absorption in the heat of midday.
24. a) The hypothalamus is both the receptor and control centre for regulation of body temperature. Blood flowing through the hypothalamus is constantly monitored by special, heat-sensitive cells lining the blood vessels. If body temperature is even slightly high or low, the hypothalamus sends nerve messages to various effector organs to either warm or cool the body back to its correct temperature. b) The peripheral blood vessels are “effector organs” for temperature regulation. Veins and arteries can be constricted (narrowed) to reduce the blood flow to the skin. This reduces the amount of heat lost through the skin, thereby helping to warm the body. The opposite process of dilating (widening) the blood vessels allows more blood flow to the skin. This allows more heat to be lost from the skin, thereby cooling the body. c) Three other effector organs: Sweat glands (perspiration), skeletal muscles (shivering), thyroid gland (hormone thyroxine), body hair muscles (goose bumps).
28. a) Oxygen is carried attached to the haemoglobin molecules in the red blood cells. Most carbon dioxide is carried in solution in the blood plasma as bicarbonate ion, HCO3-. b) C6H12O6 + 6O2 6CO2 + 6H2O + ATP c) The high concentration of dissolved CO2 causes the pH to be slightly lower (because CO2 reacts with water forming carbonic acid). This change in pH causes a change in the shape of the haemoglobin molecule, which causes it to release oxygen, which can then diffuse into the surrounding body cells.
HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
27. Arteries have thick, muscular walls. This allows them to withstand the high pressure blood they carry as the heart pumps. Being elastic, the walls can expand outwards under pressure, then contract and help squeeze the blood on its way. Veins have thinner walls since the blood they carry back to the heart is at low pressure. Veins are equipped with valves to prevent back-flow. The thin walls of a vein allow them to be compressed by neighbouring muscles, which helps squeeze the blood forward.
29. Red Cell Concentrate contains about 2x as many red cells as normal blood. It is used to treat people with severe anaemia, or following severe blood loss. Platelet Concentrate is given to patients who need extra bloodclotting capability, such as leukemia sufferers.
31
www.keepitsimplescience.com.au
keep it simple science
TM
Baulkham Hills High School SL#802445
34. a) The insect equivalent of kidneys are the “malphigian tubes” which run all though the body and collect and concentrate nitrogenous wastes in the form of uric acid. Since this is basically insoluble, the “urine” can be concentrated to a semi-solid paste by reabsorbing virtually all the water, before passing the wastes into the rectum for excretion with the digestive wastes. This means there is virually no loss of water during excretion.
30. Vessels involved Substances transported Processes involved
Transpiration Xylem
Translocation Phloem
Water & dissolved Nutrients, especially minerals sugars Passive transport Active transport
31. Water is the solvent of life All the chemical reactions of metabolism take place in water solution, and the transport of materials in cytoplasm, blood or phloem takes place mainly in water solution. Water is involved in life chemistry Water is a reactant or product of many metabolic reactions. The reactions of photosynthesis and cellular respiration are just two of the many examples. Water is vital in temperature regulation Water has a very high specific heat capacity. This helps stabilize the temperature of all living things.Evaporation of sweat is an important cooling mechanism in mammals. Water supports and cushions cells and organs Animals such as worms rely on the hydraulic pressure of water in their tissues to support their body and maintain its shape. In vertebrate animals the water solutions in the tissues helps to cushion organs against bumps and impacts. (eg cerebrospinal fluid around the brain)
b) The Spinifex Hopping Mouse is a desert-dweller which produces very small amounts of very concentrated urine. This is achieved because: • the nephron tubules are very long, allowing for more reabsorption of water, and less volume of urine. • the cells lining the tubules are able to actively transport urea from the blood into the urine. This allows the urine to be even more highly concentrated than in other mammals. 35. a) Enantiostasis is a special case of homeostasis, in which an organism maintains a stable internal environment despite significant changes in the environment around it. An example of a habitat where this is important is a tidal estuary, where the tides cause the salinity of the environment to fluctuate. To maintain their “osmotic balance” while their evironment changes from virtual fresh water, to salty and back again, requires estuarine organisms to cope by strategies such as: • burrowing into the mud where the salinity is more constant. (eg crabs & yabbies) • adjusting the functioning of their kidneys from water excreters to water conservers as the tides change. (eg fish)
32. Filtration occurs in the glomerulus. Some of the water of the blood plasma and its dissolved sugars, minerals, urea etc seep out of the blood vessel, like water through a filter paper. Blood cells and proteins cannot leak out. This “filtrate” flows along the renal tubules where reabsorption occurs. Useful nutients (sugars, amino acids) are actively transported back into the bloodstream. Most of the water in the filtrate flows back to the blood by osmosis. A portion of the water with dissolved urea flows on to be excreted as urine.
b) Spinifex Grass has fine hairs all over its leaves. This traps a layer of still air near the leaf, reducing the evaporative effect of the wind. Gum trees, such as the River Red Gum, has leaves with very few stomates, and a thick, waxy cuticle to minimize water losses. c) Mangroves: • secrete salty brine onto the leaf surface. This washes away when it rains. • accumulate salt in older leaves which are then shed, carrying away a load of excess salt.
33. ADH is secreted by the pituitary gland (under control of the hypothalamus) It alters the permeability of the renal tubules to water. Increased ADH allows greater water reabsorption, and less urine production. Aldosterone is secreted by the adrenal glands. It stimulates the cells lining the renal tubules to actively transport more sodium ions back into the blood from the renal fitrate. This retains more salt in the body to adjust “osmotic balance”.
NOTICE ANY ERRORS? Our material is carefully proof-read but we’re only human If you notice any errors, please let us know HSC Biology Topic 1 copyright © 2005-2007
keep it simple science
32
www.keepitsimplescience.com.au
