Experiment to Shoew the Effect of Different Concentration of Glucose on Potato Strips

Topics: Osmosis, Concentration, Cell wall Pages: 5 (1248 words) Published: July 20, 2012

INTRODUCTION: Molecules of liquid and gas are constantly in motion, they move randomly in all directions and bounce around in all directions and bounce around and into each other. As they move, they tend to spread out moving from areas with many molecules to areas with fewer molecules . This process of spreading out is called Diffusion, for example smell of cooking travelling around the house from the kitchen, circulation of oxygen from the alveolar air space to the lungs, smell of perfume in the air.

However there is a specialized type of diffusion called Osmosis. This is when water molecules moves from a region of high concentration of water to a region of low concentration of water thru a semi-permeable membrane. Osmosis will only occur thru a semi-permeable membrane (that is a membrane which selectively allows passage of certain types of molecules through it while restricting the movement of others) Examples of Osmosis includes

a)The absorption of water by plants roots to maintain shape and stiffness. b)Elimination of wastes such as sweat and urine
c)Movements of water and other solvents membranes thru cell walls/membranes.

AIMS: This experiment is going to look at the effect of different concentrations of glucose (Independent variables) on potato strips (dependent variables) of the same length and variety under the same condition.

HYPOTHESIS: Plants cells behave differently in glucose solution of varying concentration by a process known as Osmosis. Plants cells will go flaccid or shrink in an hypertonic solution, a solution with low water concentration and high glucose concentration as water will move from the cell (high water concentration) to its surrounding. Turgid (swell up) in hypotonic concentration a solution with high water concentration and low glucose concentration due to water moving from surrounding high water concentration into the plant cell causing it to swell up, and no change in an Isotonic solution, a solution in which concentration of water and glucose are the same. Therefore it can be predicted that the potato strips with highest glucose concentration will loss the most water by Osmosis. This will be characterised by reduction in its size and could lead to Plasmolysis.

Plasmolysis is the shrinking of protoplasm away from the cell wall of a plant due to water loss from Osmosis, thereby resulting in gap between the cell wall and the cell membrane. On the other, in the solution with zero concentration of glucose the reverse will be the case because water will be drawn into the potato strip by Osmosis thus resulting in an increase in its mass.

APPARATUS: Cork borer, white tiles, five test tubes, ruler, knife, glucose solution, distilled water, dropper, tissue paper.

METHOD: Five test tubes were labelled 1,2,3,4,&5. Potato strips was peeled and five small strips were bored using a 2mm cork borer on the white tiles weighed on the scale and recorded. Solution was made by mixing varying concentration of glucose with varying volume of water as shown in the table below. The potato strips were added noting the volume of the solution in the test tubes. The test tubes were placed in a rack and kept in the fridge for seven days. After seven days the potato strips were removed from the test tube and dried with tissue (this is to prevent any irregularities) before measuring the mass of the potato strips and recording it. The sizes of the potato strips were exactly the same as the same cork borer (2mm) was used for five strips ,same variety of potato was used (Maris pipers),similar test tubes were used under the same temperature. The stripes were all reweighed after seven days and all the five stripes were dried with tissues before weighing to prevent irregularities. Protective clothings such as lap coat was worn during the experiment and extra care was taken when using the knife in cutting the...
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