Investigating the factors affecting the rate of osmosis in potato cells.

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Nicholas Moore 11Mc Group Q

Investigating the factors affecting the rate of osmosis in potato cells

Introduction

Osmosis is a physical process that occurs in plant and animal cells when there are molecules in a high concentration inside (or outside) the cell, and there is a low concentration outside (or inside) the cell. The process which then occurs is similar to diffusion, but with a small difference.

Diffusion is the movement of particles of a substance from a high concentration to a low concentration.

Osmosis is the movement of particles of a substance from a high concentration to a low concentration through a partially permeable membrane. In the case of a plant cell, this may mean that water would move into a plant cell if there was a higher concentration of water outside the cell than inside. However larger molecules either could not pass through or would pass thorough very slowly:

Flow of water molecules

The above diagram shows what might happen when the potato cylinder is put in to the Petri dish with distilled water in it. The water molecules are moving from the high concentration of them

        In this investigation we aim to investigate the factors affecting the rate of osmosis in a plant cell.

There are several factors which would affect the rate of osmosis in potato cells, though not all of them are within our capabilities to test them. The potatoes would be put in a sucrose solution to investigate some of the factors affecting rates of osmosis, such as these:

Pressure – if there is a higher pressure surrounding the potato cells, they will absorb more water and quicker as it will be forced through.

Concentration of solution – the higher the concentration of the solution used, the more water will flow out of the cells at a higher rate. The lower the solution’s molarity, the more slowly the water will flow out of it, and possibly it will flow into it.

Heat – if the water molecules are more agitated they will flow faster in the direction of the concentration gradient.

Surface area of potato – the more surface area the potato cells have, the faster the rate of osmosis will be, as more cells will be in contact with the solution.

The easiest and most accurate of these to measure is concentration, as concentration can be easily controlled and quite easily measured. Different molarity solutions of sucrose can be composed and used along with certain amounts of potato to find the rate of osmosis.

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Hypotheses

I predict that the potato cylinders in the higher concentration sucrose solutions are more likely to lose mass through osmosis, and in the lower concentration solutions the potato cylinders would gain mass – especially in the distilled water. I predict the rates of osmosis will look like this:

As we can see from my graph prediction, I think that the two lowest molarities – distilled water and 0.2 mol will increase the mass of the potato cylinder, whereas I think that from ...

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