The Factors Affecting Osmosis in Potato Tissue

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The Factors Affecting Osmosis in Potato Tissue


In this coursework I am investigating the factors affecting osmosis in

potato tissue.


Osmosis is defined as the net movement of water molecules from a

region in which they are highly concentrated to a region in which they

are less concentrated. This movement must take place across a

partially permeable membrane such as a cell membrane, which lets

smaller molecules such as water through but does not allow bigger

molecules to pass through. The molecules will continue to diffuse

until the area in which the molecules are found reaches a state of

equilibrium, meaning that the molecules are randomly distributed all

over an object with no area having a higher or lower concentration

than the other.

Plant cells always have a strong cell wall surrounding them. When they

take up water by osmosis they start to swell, but the cell wall

prevents them from bursting. Plant cells become turgid when they are

put in dilute solutions. The pressure inside of the cell rises and

eventually the internal pressure of the cell is so high that no more

water can enter the cell. The liquid pressure works against osmosis.

Turgidity is very important to plants because this is what makes the

plants stand up to the sunlight. When plant cells become flaccid this

is when they loose water by osmosis this is the exact opposite of

turgid. The content of the potato cell shrink and pulls away from the

cell wall.

To create a fair test certain parts of the experiment will have to be

kept the same whilst one other key variable is changed. I have chosen

to change the concentration of the external solution each time. This

will give me a varied set of results. If any of the other variables

were not kept the same then it would not be a fair test, for example

if one of the potato chips was a different length to the rest this

would affect the results and therefore would conclude in an unfair
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