The Effects of Osmosis on Potato Cells

The Effects of Osmosis on Potato Cells

Introduction

The aim of this investigation is to see the effect of varying

concentrations of glucose solution on the amount of osmotic activity

between the solution and a potato chip. An investigation into

Plasmolysis in onion cells was undertaken prior to this experiment, in

order to gain some knowledge of osmosis to enable a hypothesis to be

formed.

Preliminary Work and Scientific Knowledge

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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, like a cell wall, which allows small

molecules like water through but does not let larger molecules

through. The molecules continue to diffuse until the area in which

they are found has an even distribution of molecules all round, inside

and outside of the cell. Naturally, an environment that is identical

inside and out of the cell is the best condition to survive (i.e. the

'perfect' environment).

In the case of the onion cells, when placed with a drop of water,

after 15 minutes, the cell had a turgid, or swollen, appearance under

the microscope and felt fairly strong and sturdy, as the water was

diffused through osmosis into the cell. This is because pure water has

a 100% concentration of water, and the onion cell has much less, so

the water diffused from a higher concentration to a lower

concentration. With the 1% glucose solution, the cell had a flaccid

appearance and the onion felt particularly floppy, because the cell

membrane is pulled into the cell when the vacuole shrinks. This is

what Plasmolysis is, the shrinkage of cell cytoplasm, with the

membrane being pulled in. This happens because the water inside the

vacuole moves outside the cell as the 1% glucose solution is a

stronger solution than the solution in the vacuole, resulting in there

being a higher concentration of water inside than out.