Chapter 2

CHAPTER 2: CHEMISTRY OF LIFE -

Artificial Fats  – “Olestra”  carbohydrate + particular kind of fat  is not digested/absorbed Artificial Sugars  – 1937  ‘cyclamate’  30x sweeter (sucrose)  chemical compounds  sulfamates - ‘Nutrasweet’  aspartame  200x sweeter

2.1: Nutrients

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Macromolecules – (macro = large) large organic polymers (poly = many, mer = part)  large molecules consisting of many identical or similar subunits (monomers connected together). Unity – only about 40-50 common monomers are used to construct macromolecules Diversity – new properties emerge when these universal monomers arrange in different ways. all permanently made up of elements C, H, O, N

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Nutrients – carbohydrates, proteins, and fats (lipids).

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Polymerization Reactions 2+ small monomer molecules  larger molecules with repeating structural units  or making 3 dimensional networks/ polymer chains Condensation Synthesis/Dehydration Synthesis Hydrolysis Making  – 2+ monomers  covalently linked together; (hydro = water, lysis = loosening)  – reaction breaks water molecule removal for each linkage (one loses OH, covalent bonds between monomers and the hydroxyl other loses H)  enables macromolecules. Process (neutral OH) bonds to the adjacent monomer. requires energy, catalyst, or enzymes.

2.2: Carbohydrates -

Body’s most important source of energy  organic molecule made of sugars and their polymers (formed by condensation reactants. The classification is based on # of sugars). Structural material-plant cell walls

Simple Sugars: Monosaccharides

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(mono = single, saccar = sugar)  contains C, H, O in the ratio of 1:2:1. Formula = n(CH2O). Major nutrients for cells  glucose  most common single sugar (C6H1206). Can be produced from CO2, H2O + sunlight, and can exist in chain form as well as ring form (in nature). Six carbon chain with an aldehyde

Combining Single Sugars: Disaccharides

Complex Carbohydrates: Polysaccharides

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Size of carbon skeleton varies 3-7 carbons

Fructose  appears in fruits. Six carbon chain with a ketone. Galactose  found in milk. Six carbon chain with an aldehyde (different hydrogen arrangement) Deoxyribose  single sugar component of DNA molecule. Five carbon chain with an a ldehyde. Their carbon skeletons are raw materials for other organic materials Maltose  2 glucose (malt sugar used in making beer) (starch) Sucrose  glucose + fructose (table sugar  sugar cane) Lactose  glucose + galactose (found in milk) Starch  most plants  2 polysaccharides, amylase, amylopectin  found in plants, stores energy Cellulose  many glucose units  – cell walls in plants Glycogen  resembles starch molecule  animals, carbs storage (found in liver and in muscles)

2.3 Lipid -

1) fats, oils, waxes, 2) phospholipids, 3) steroids Insoluble in water, only in acetone (nail polish remover), alcohol, ether, chloroform Also has C, H, O  in different proportions from carbohydrates Glycogen supplies are limited  if full, excess carbs  fat Supply Energy  difficult for body to break down  longer satisfaction 1 g of lipid = 2 g carbohydrates or proteins More compact fuel reservoir than carbs Aids in absorption of vitamins Serves as insulation against heat loss for body Are key components in cell membranes Cushions organs Act as raw materials for synthesis of hormones, other chemicals Most common type of lipid  – triglyceride = one glycerol molecule + three fatty acids (formed by dehydration synthesis reaction)

Functions

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FATS

Saturated Fats Fatty acid  only single bonds between carbon atoms  maximum number of  Hydrogen atoms possible on carbon skeleton Usually solid at room temperature Firmer fat (e.g. lard, butter) Strong chemical bonds  permit cooking at higher temperatures Most animal fats -

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Unsaturated Fats One or more double bonds between carbons in fatty acid tail, a result of missing Hydrogen atoms Tail curves at each C=C  molecules are not packed closely enough to solidify at room temperature, is usually viscous Most plant fats (described as polyunsaturated)  corn, peanut, olive oil. React more easily  broken down faster -

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Hydrogenation – H atoms added to unsaturated plant fats to make them firmer PHOSPHOLIPIDS – 1 phosphate group + 2 fatty acids + (attached to) glycerol backbone Main component - well suited to cell membranes. Polar end  soluble in water, 2 fatty acids  nonpolar water. (hydrophilic head, hydrophobic tail)  soluble in water. Soap (made from fats treated with lye (NaOH)  dissolves oil and grease in water. STEROIDS – C,H,O  insoluble, carbon based, multiple ring structure. Lipids which have four fused carbon rings with various functional groups attached. Cholesterol  – function  makes certain hormones (male + female), important part of cell membrane. When combined with other fats, it forms a plaque that blocks blood vessels  reduced blood flow to tissue causes lack of oxygen, nutrients = heart disease + circulatory problems

2.4 PROTEINS -

C, H, O, N, sometimes S atoms

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Macromolecules made up of amino acids Proteins manufactured (when cells are damaged) or (building structures for new cells) : proteins created to build red blood cells = rate at which they die (1 mill/sec). Important in controlling cellular functions + genetic operations. Enzymes Proteins: controls rate of many reactions  digestion, cellular respiration. Storage of Foods Emergency situation: can be used as energy source Composed of 20 amino different amino acids (composed of  N, C, H O )(the order and # determine the type)  sequencing is regulated by genes located on chromosomes. Gene  patterns of nucleotides (basic structural units of nucleic acid). Each unit  5 carbon sugar, 1 phosphate, nitrogenous base. Proteins can contain 8-4000 amino acids. There are over a thousand different variations of sequences. A chain of several amino acids  polypeptide Necessary Amino Acids: 12 : H uman-made Essential Amino Acids: 8: methianine, valine, lysine, tryptophan, threonine, phenylalanine, leucine, isoleucine: must be obtained from food.

Functions

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Building Cell Structures

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Denaturation: physical, chemical factors (heat, radiation, change in pH) disrupt bonds between amino acids, changing configuration. It may uncoil, assume new shape  change in physical properties, biological activities

Coagulation: permanent.

Research in Canada: Proteins

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Membranes of cells  links  receive + transport info, nutrition, medication. The key are transmembrane proteins (modified proteins, acting as channels for certain ions going in and out of cells  shortage or mutation causes diabetes, multiple sclerosis, cystic firbosis, muscular dystrophy, cancers) Specific molecular structure  helps scientists deduce molecular mechanism behind diseases. Dr. Deber  isolated + cloned key segments of defective membrane protein  cystic fibrosis  hopes to gain insight into molecular defects which lead to this disease. Translation (protein synthesis) The patterns of nucleotides are used as templates to build messenger RNA (mRNA) during a process called: Transcription. (instructions from DNA copied onto mRNA) mRNA leaves the nucleus and attaches to ribosomes in the cytoplasm (where instructions are read) the other type of RNA in cytoplasm (transfer RNA tRNA) is attached to a specific amino acid tRNA is brought into position  joins w/ mRNA  ribosome. Each amino acid is brought into correct position to build the protein. Amino acid chain growing from ribosomes is dropped inside endoplasmic reticulum membrane. Chain folds into protein Protein moves to Golgi Complex for additional processing and for sorting Protein moves to plasma membrane for export

2.5 NUCLEIC ACIDS -

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DNA and RNA  not nutrients essential for life Structure DNA RNA Sugars, phosphate groups, 4 Sugars (different one), phosphate groups, 4 nitrogenous bases nitrogenous bases (A adenine, (A adenine, G guanine, C cytosine, U uracil) G guanine, C cytosine, T Single strand thymine). These are bonded together in a subunit  nucleotide Nitrogenous bases of  adjacent DNA nucleotides  always pair A-T, G-C Double helix shape  – two strands of DNA coiled + attached with bonds between nitrogenous bases. Structure determined by Watson and Crick.

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Proteins (long chains of amino acids)  responsible for structural + functional characteristics. Organisms must contain different proteins. Number an d sequence  unique characteristics. Sequence of proteins  determined by sequence of nucleotide bases in segment of DNA  gene. Each of the genes  codes for production of 1 protein (corresponding sequence of amino acids). One gene, one protein hypothesis. Each of the amino acids  coded by triplet of bases (4cubed = 64 different base triplets possible for the 20.)  all have more than 1 DNA base triplet code  a gene on DNA  has at least 3 times as many bases as there are amino acids in the protein it codes for. Base-pair sequences, number of base pairs in sequence of DNA molecule (thousands of base pairs) are almost endless  great diversity in genetic code.

2.6 THE LIVING CELL MEMBRANE -

The cell membrane separates the cell’s protoplasm from external environment  what enters, leaves Nutrients from environment, waste builds up  disposed

Structure: bilayer of phospholipids, variety of protein molecules  embedded within phospholipid layers many carry special sugar molecules  glycoproteins  provide cell with unique identity  vary between organisms  distinguish type A red blood cell from type B. Immune system recognizes foreign invaders  unique glycoprotein structure  cell membrane Protein molecules  act as gatekeepers (opening and closing pathways), receptor sites for hormones (chemical messengers  allow cells to communicate with one another), or transport (using cell energy to pick up needed materials and move them in and out of cell) Liposomes and Aquaculture 1965  – Alec Bangham  lipids can initiate their own assembly into double-layered spheres the size of a cell (liposomes)  function like cell membranes  can fuse with cell membrane + deliver contents. Used today to help drugs target tumours  reduces side effects of drug interactions on healthy tissues. Enables patients  to accept higher doses of anti -cancer drugs Liposomes as delivery  efficiency of gene therapy  introducing new genes into DNA to correct genetic flaws/disease

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2.7 PASSIVE TRANSPORT

Passive Transport Movement of materials across cell membrane without the use of energy from the cell Diffusion: net Molecules moving from area of high concentration  low  result of Brownian motion: random movement of molecules in gas or solution. movement of 

particles down an electrochemi cal gradient (give up potential energy)

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Osmosis: diffusion of  water across a selectively permeable membrane

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Diffusion rates increase  hotter temperature (liquid)  pressure increases (gas)  molecules are bunched close together, collide more frequently. Therefore, gas  high pressure  low pressure. Diffusion affected by  concentration, temperature, pressure (continues until equal distribution) Oxygen + CO2 move across cell membranes  diffusion. O diffuses from blood  areas of high  low concentration in the cell. CO2  accumulates inside cell  diffuses from cell  blood. Water  follows concentration gradient  – difference in # of molecules or ions of a substance between adjoining regions. Molecules tend to diffuse  – high concentration 

low. Water  side B to side A  concentration of water molecules + protein molecules = equal  equilibrium. (all acting influences are balanced  stable environment). Ideally, cells are bathed in isotonic solutions (solute concentration outside cell = that inside of cell). Blood keeps internal environment in homeostatis (keeping isotonic balance  constant internal environment). Hypotonic solution  lower concentration of solute  higher concentration of water than inside cell. Water moves inside cell. In freshwater, organisms have developed ways of expelling water  contractile vacuole. Hypertonic solution (greater)  concentration of solutes  higher than in cell + concentration of water  – lower. Water moves out by osmosis. * Turgor pressure  water pressure. Seen from the extracellular fluid point of view (ECF) Protein carrier molecules in cell membrane  aid in passive transport. They speed up the Facilitated movement of molecules already moving across c ell membrane. (e.g. glucose diffuses into Diffusion red blood cells 100x faster than other sugar molecules  carrier proteins must be specialized to aid diffusion). 3 ways to enter cell: through phospholipid bilayer, protein channels, facilitated diffusion. 2.8 ACTIVE TRANSPORT

Molecular Active Transport Cell uses energy to move from low high concentration (against concentration gradient). Happens while you sleep, (30% - 40% of total energy budget) (uses ATP energy) Exocytosis Process  cells ingest materials too large for Exocytosis: large molecules transport carrier molecules. Membrane folds around material, within the cell  transported trapping ingested particle in pouch/vacuole inside cytoplasm. out (waste, transmitter Enzymes from lysosomes  used to digest molecules. 2 types: chemicals from nerve cells) Pinocytosis  – cells take up dissolved molecules by engulfing Golgi apparatus  fuse with small volumes of external solution (liquid droplets). (e.g. cells cell membrane + material  in small intestine  fat droplets) released Phagocytosis  engulf solid particles. White blood cells  phagocytes (eater cells)  consume invading microbes. These are trapped in vacuole  digested when vacuole fuses with lysosomes. Some membrane proteins  unique shape to match specific molecules in endocytosis