Lab Report Diffusion and Osmosis

Lab Report Diffusion and Osmosis I.

Title

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II.

Introductio Introduction n

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Diffusion Diffusio n and Osmosis

Plasmolysis Plasmolysis is the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis. The reverse process,cytolysis, can occur if the cell is in a hypotonic solution resulting in a higher external osmotic pressure and a net flow of water into the cell . Through observation of plasmolysis and deplasmolysis it is possible to determine the tonicity of the cell's environment as well as the rate solute molecules cross the cellular membrane . Diffusion Molecules are in constant motion and tend to move from regions where they are in higher concentration to regions where they are less concentrated . Diffusion is the net movement of molecules down their concentration gradient . Diffusion can occur in gases, in liquids, or through solids . An example of  diffusion in gases occurs when a bottle of perfume is opened at the front of a room . Within minutes  people further and further from the source can smell the perfume . Osmosis Osmosis is a specialized case of diffusion that involves the passive transport of water . Inosmosis water  moves through a selectively permeable membrane from a region of its higher concentration to a region of  its lower concentration. The membrane selectively allows passage of certain types of molecules while restricting the movement of others . Hypertonicity A hypertonic solution is a solution having a greater effective osmole concentration than the cytosol . It contains a greater concentration of impermeable solutes on the external side of the membrane . When a cell¶s cytoplasm is bathed in a hypertonic solution, water will be drawn into the solution and out of the cell by osmosis . If water molecules continue to diffuse out of the cell, it will cause the cell to shrink, or  crenate. A hypertonic solution is used in osmotherapy[1] to treat cerebral hemorrhage . Hypotonicity A hypotonic solution is a solution having a lower effective osmole concentration than the cytosol . It contains a lesser concentration of impermeable solutes on the external side of the membrane . When a cell¶s cytoplasm is bathed in a hypotonic solution the water will be drawn out of the solution and into the cell by osmosis . If water molecules continue to diffuse into the cell, it will cause the cell to swell, up to the point that cytolysis (rupture) may occur . In plant cells, the cell will not always rupture . When placed in a hypotonic solution, the cell will have Turgor Pressure and proceed with its normal functions .

Isotonicity

A condition or property of a solution in which its effective osmole concentration is the same as the solute concentration of another solution with which it is compared . It is a concentration of both water and total solute molecules are the same in an external solution as in the cell content . Water molecules diffuse through the plasma membrane in both direction . The rate of water diffusion is the same in both direction that cell will neither gain nor lose water .

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To observe about osmosis and diffusion process

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Differentiate between hypertonic, hypotonic and isotonic

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Examine

the effects of osmosis on plant cells

Materials/Ingredients

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Experiment

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1:

2:

A glass of water  A glass of NaCl 10 % Measure balace a potato (2 cube, 1cm x 1 cm) a carrot (2 cube, 1cm x 1 cm) a tuber (2 cube, 1cm x 1 cm)

Experiment

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A Microscope Microscope slide Cover slip A slice of Rhoeo discolor 

Experiment

V.

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Goal

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3:

Two glass of water  Pipet Methyl blue Eosin Methods

Experiment

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1:

1. Prepare all the materials . 2. Cut a slice of Rhoeo discolor (the purple part) .

3. Put it on the microscope slide, add with a drops of water, cover it with cover slip, check the structure inside the cells by microscope, draw it . 4. Dry the cells by tissues, and drop a drops of sugar %, check the structure inside the cells again, draw it and compare it with the first draw (especially the stomata) . Experiment

1. 2. 3. 4. 5. 6. 7.

Prepare all the materials . Cut the potatoes, carrots, and tuber , with a cube shape in 1cm x 1cm dimension Measure the mass with measure balance, write it . Prepare two glass, one is for a tap water and the other for NaCl 10% . Put inside each of the potato, carrot, and tuber . Wait until 15 minutes . After that, re-measure it again, compare the mass .

Experiment

1. 2. 3. 4. 5.

VI.

2:

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3:

Prepare all the materials . Prepare two glass of water, with the same amount of water . Drop just one drop methyl blue in one glass, and drop eosin in the rest . Watch the spread of the solute, count with the stopwatch . Look and compare how much the time to spread to all part of the glass .

R esult

Experiment

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and Discussion

1:

Before

After(add sugar)

The stomata still clearly seen .

Experiment

Medium

The stomata is open and broken .

2: The object

Mass

(g) Tap Water

Potato

before

Mass

After (g)

Change in mass (g)

Explanation

Carrot Tuber  Potato Carrot Tuber 

NaCl 10%

Experiment

3:

Difussion= -Methyl Blue (add one drop to the 29 ml water) Time to spread

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5 minutes 10 seconds

-Eosin (add one drop to the 29 ml water) Time to spread

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3 minutes 6 seconds

Discussion Why??

Conclusion

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The factor why there is an error in our observation: -

 NaCl mot spread well inside the water  The measure balance not quite accurate

The factor why eosin is more faster to spread than methyl blue Movement of Molecules in Cells Cell membranes are selectively permeable .

VIII.

R eference

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http://www. phschool.com/science/biology_place/labbench/lab1/concepts .html http://en.wikipedia .org/wiki