Investigation of osmosis in potato strips by measuring the length of the strips after a incubation in various sucrose concentrations

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Name : Rand IshaqBiology lab report2011-09-19

Investigation of osmosis in potato strips by measuring the length of the strips after a incubation in various sucrose concentrations

Aim: the aim is to investigate the effects of Osmosis through selectively permeable membranes (potato cells) when placed in different solute concentrations for 30 minutes.  

Research question: how do different solute concentrations after 30 minutes incubation affect the length of potato strips?

General background:   in living organisms. The processes of diffusion and osmosis happen frequently as means of cellular passive transport. Firstly diffusion is the random movement of molecules from an area of higher concentration of those molecules to an area of lower concentration, while osmosis is a special case of diffusion. Osmosis is the diffusion of water through a selectively permeable membrane that allows for diffusion of certain solutes and water) from a region of higher water concentration to a region of lower water concentration.

 When two solutions have the same concentration of solutes. They are said to be isotonic in relation to each other. If the two solutions are separated by a selectively permeable membrane. Water will move between the two solutions. But there will be no net diffusion of water between the two solutions resulting in, that the concentrations will remain the same in relation.

If there is a difference between two different solution concentration. The one with highest solute concentration is hypertonic in relation to the one with lowest solute concentration. The solution with the lowest solute concentration solute is hypotonic to the one with high solute concentration (hypo means under or less than). These words can only be used to compare solutions.

Considering that two solutions are separated by a selectively permeable membrane. The solution that is hypertonic to the other has higher solute concentration and therefore the water concentration is lowered compared to a hypotonic solution where the solute concentration is lower and the water concentration is higher. So the net movement of water will be from the hypotonic solution into the hypertonic solution.

Hypothesis: 

My prediction is that Osmosis will take place in all the beakers, in the 0.0 mol*dm-3 concentration solution , the size of the potato will increase .

In the other solutions (0.2, 0.4, 0.6, 0.8 and 1.0) mol*dm-3 in sucrose concentration) osmosis will occur and the water will move from the hypertonic solute to the hypotonic solute. I.e. From the potato tissue into the surrounding solute concentration of sucrose in the beaker.

The variables:

The dependent variable: the length of potato strips in mm.                                                                                                                                                                                                               The Independent variable: Different concentrated solutions of sucrose (0.0 /0.2 / 0.4 / 0.6/0.8 /1.0 mol dm-3   )

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The controlled variables:

Materials needed:

30 pieces of potato strips with the following dimensions:  (0.5cm x 0.5cm x 4.0cm)

6 beakers of size 50ml

Knife

Ruler ( measuring up to 15cm)

 6 different  sugar (sucrose) solute concentrations :  

0.0 mol dm-3 ( distilled water )

0.2mol dm-3

0.4 mol dm-3

0.6mol dm-3

0.8mol dm-3

1.0mol dm-3

The method:

The different Sugar solutions were poured a beaker and each beaker was marked according to the concentration of sucrose poured into it .

Potato pieces were cut into 30 strips using a ruler and ...

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