Research Question: How does variation in temperature affect the permeability of cell membranes?
Background Information: In this investigation I will want to identify how variations in temperature effect the permeability through the use of a beetroot. I predict that as the temperature of the water increases so will the dispersion of the pigment.
Independent Variable: The temperature of water will be increased in increments of 10oC, thus the temperatures I will be using are 20oC, 30oC, 40oC, 50oC and 60oC.
Dependent Variable: I will be measuring the cell membrane permeability through the amount of pigment dispersion. A colorimeter will be used to quantify results into a percentage transmission of light, after it is left for 5 minutes.
Control Variables:
Variable
How it is measured
Why it needs to be measured
Mass of beetroot cylinder
A weighing scale should be used to ensure all beetroot cylinders weigh 1 gram.
If the mass of the beetroot cylinder varies it may cause a difference in diffusion capabilities.
Length of beetroot cylinder
The in order to ensure the surface area is kept the same, each cylinder must be 2 cm long. This should be measured using a 15cm ruler.
If the lengths are different it would result in a difference of surface areas therefore questioning the test’s accuracy.
Age of the beetroot
To keep the age of the beetroot the same, the same beetroot will be used to extract the cylinders.
Different ages can cause the amount of pigment in the beetroot to fluctuate. Therefore it is vital to use the same beetroot.
Volume of water
A 25ml measuring cylinder should be used to accurately measure 15ml of water for each test tube.
Water is a solvent and only a certain amount of pigment can be absorbed by the water. Hence it would create a contrast in water potential.
Time
Each cylinder will remain in its test tube for 5 minutes before the water is removed and tested. A stopwatch must be used.