Osmosis In Potato Tissue

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OSMOSIS IN POTATO TISSUE

GCSE Biology – Experiment report

Osmosis is a specialised form of diffusion, a process in which molecules move across a semi-permeable membrane. Osmosis applies specifically to water molecules that behave in this way, moving from a region of high water concentration to a region of low water concentration. Also known as moving down a concentration gradient, this movement can be best described below:

             

               

                                                                                N.B – The sugar particles are too large

to pass through the

                                                                                             semi-permeable

membrane.

D

The process happens only in one direction, as shown by the arrows in the diagram above. It is important to remember that osmosis will take place whenever two solutions of water of differing concentrations, are separated by a selectively permeable membrane.

Osmosis takes place throughout both plant and animal cells, and has differing effects in both mediums. Because all plant cells incorporate a rigid cell wall, plant cells are allowed to swell and become turgid. This process of turgor is an important feature of land dwelling plant-life. The turgor causes support for leaves, enabling photosynthesis to take place.

       

   

In animal cells, osmosis has a very different effect. If a blood cell were immersed in water, it would swell and would eventually burst. This effect is combated by a natural clause; the concentration of the water in the cells is the same as the concentration of that outside the cell, in the bloodstream.

In any investigation, the variable aspects of the experiment must be taken into careful consideration. This investigation will explore the phenomena of osmosis and discover what effect, if any, changing the concentration of the solution around the cell will have. For this particular study, small tubes of potato tissue will act as the cell under scrutiny, and the tissue will be surrounded by a sugar solution.

Although this experiment is dealing with only one significant factor that influences the osmotic process, it would be unnecessary to discount the other variables.

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  1. Firstly, the surface area of the potato tubes has an effect on the rate of osmosis taking place. A larger surface area would take up more water, likewise a smaller surface area would have an opposite effect.
  2. The size of the water and sugar particles also comes under consideration. If the sugar molecules are smaller than the breaks in the selectively permeable membrane, they will diffuse through into the potato and osmosis would not take place. Also, using a smaller water molecule would have an adverse effect; more molecules would be allowed to pass through the membrane ...

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