The Effect of Concentration of Water in a Saline Solution On the Process of Osmosis in a Potato

The Effect of Concentration of Water in a Saline Solution On the Process of Osmosis in a Potato

Aim

The aim of this experiment is to find out what effect the

concentration of water in a saline solution has on the process of

osmosis in a potato.

Osmosis is a specialised case of diffusion involving water diffusing

through a semi-permeable membrane. Semi-permeable membranes are very

thin layers of material that allow some things to pass through them

but prevent other things from passing through. The way it determines

what can pass through is by size i.e. small molecules pass through

whilst larger molecules don't. A cell membrane is an example of a

semi- permeable membrane and it is this that the water passes through

in osmosis. The cell membrane also lets through other small molecules

such as oxygen, glucose, ammonia and amino acids, but these do not

play a role in osmosis. In osmosis the side with the lowest water

concentrate will be the side that receives the water molecules from

the side with the highest concentration of water, until the two sides

are balanced or in equilibrium. The water molecules are free to travel

both ways but more will come from the side with the highest water

concentration than will leave the side with the lowest water

concentration. The net result of this is that the side with the lowest

water concentration will gain water, and if it is a cell, swell up.

Osmosis will not occur again once the process is in equilibrium and so

will only start up once the concentration gradient is unbalanced.

In a human body this can happen in two ways. The first of these is

that the cells use up water in respiration and so...

... middle of paper ...

...ns were all approximately the same weight and this

can be attributed to the weight or a number of other factors.

These other factors could be variations in the room temperature, the

way in which the concentration was mixed up on different days or even

the pressure potential of the cell. In an ideal experiment where all

the factors could be controlled exactly and you could ensure that it

was a fair test, then I believe the weight of the potato would be

directly proportional to the concentration of the saline solution.

Unfortunately due to human error and other factors that I have already

mentioned, my experiment was not perfect and as such the weight was

not directly proportional to the concentration. My experiment was

fairly accurate however, as, on the whole, the weight did decrease as

the concentration increased.