The effect of concentration on potato discs

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John Saunders – 10R                                                                        23/9/01

What is the effect of concentration on the

size of potato discs?

Research

The main process that will take place in this experiment is osmosis. To explain osmosis more, I’ve conducted some research to help me decide what will happen in the experiment, and create a prediction, and also perhaps help me set up a good method to get the best results from my experiment.

What osmosis is:

Osmosis is the movement of water from an area of high concentration to an area of low concentration through a semi-permeable membrane.

The process of osmosis:

Salt

Water      

     

High concentration of salt                                  Semi-permeable                         High concentration of water

Low concentration of water                             membrane                                   Low concentration of salt

This generally shows the osmosis process. The semi-permeable membrane isn’t a solid wall, so molecules can get through it, but only small molecules are deceptive enough to do it. In this case, only the water can get through it, and the salt solution can’t.

Osmosis is basically where the cell tries to form an equilibrium between itself and the solvent or solute around it. In the case of this diagram above, the side with the lower concentration of salt solution (higher concentration with water), passes on water to the side with the higher salt solution (lower concentration with water), to dilute it. This is to try and form an equilibrium between the two sides of the membrane.

The biological importance of osmosis:

This is very important, because in plant and animal cells, the cell membrane will only let small molecules through it, such as water, and stops toxic molecules from entering and rupturing our cells, which could mean possible death. There are a few exceptions though, as you’ll see in the problems section.

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It is that important, marine fish even use osmosis to drink, and use their gills to excrete the salty water. Freshwater fish finds this process annoying though, because they give their water to the salty water to try and form an equilibrium they don’t want to form, and have to excrete high amounts of salty urine to stop the salt dehydrate the fish.

The biological problems with osmosis:

In plant root cells, if salt water was to get through the cell membrane, which could because of it similarity to water, it wouldn’t do great harm, but ...

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