Page 2: Contents
Page 3: Introduction
Pages 4 – 7: Preliminary Experiment
Pages 8 - 14: Main Experiment
In this experiment I am going to investigate the effect of varying concentration of a differing glucose solution on the amount of osmotic activity, between the solution and a potato tuber of a given size. The purpose of this experiment is to demonstrate how living cells rely on osmosis, the diffusion of water.
Osmosis is the movement of water molecules (H20) 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 such as a cell wall, which lets smaller molecules, such as water, through but does not allow bigger molecules, such as glucose, to do so. The molecules will continue to diffuse until the area in which they are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than another.
Investigation – Preliminary Experiment
In my preliminary experiment I am going to be seeing how potato tubers react when placed in of 0m (distilled water) 0.5m and 1m (glucose solution). I am doing this to gain some knowledge about how the potato tubers will be affected; so when I do my main experiment I will have basic knowledge on what will happen, this means I will be able to spot outliers more easily and learn from any mistakes which may have been made in the preliminary.
Molar = (m)
Mass/weight = (g)
Depending on certain factors the osmotic activity between the potato tuber and glucose solution will either increase, decrease, or unaffect the mass of the potato, such as – whether the sugar to water ratio inside the potato and outside of the potato differ or not.
Variables that could affect the amount of osmotic activity include factors such as:
o Temperature - Cells move quicker at higher temperatures, therefore the higher the temperature the higher the rate of osmosis. o Variety of Potato - Different varieties of potatoes may vary in the quantity of water and/or glucose inside them. o Volume of Glucose Solution - The more solution there is the larger quantity the glucose has to equalize over. o Pressure - Areas of different pressure have different water potentials. o Surface area - The larger the surface area, the more water can be absorbed into the cells, therefore altering the rate of osmosis.
All of these factors will affect the experiment due to the nature of the potato cells, but the only variable I will be changing is the concentration of the glucose solution.
Fair testing is essential in all investigations. If this experiment is not a fair test, i will obtain incorrect results, which could lead us to the wrong conclusions as they are not providing a true representation of the data at hand.
My prediction is that when the potato tubers are put into the distilled water, it will increase in mass; I believe this because there are more water molecules in the water than there is in the potato cells, the water molecules will move by osmosis into the potato cells through the partially permeable membrane to create equilibrium. This means that the mass of the potato piece will increase and the potato will feel turgid.
When the potato tubers are put into a high concentrated glucose solution there are more water molecules in the potato cells then in the solution; therefore the water molecules move by osmosis from the potato into the highly concentrated solution. This means that the mass of the potato tuber will decrease, and its appearance will be flaccid.
The stronger the concentration of the glucose solution the more it...