RP4

Question 1

You were provided with beetroot discs that were washed thoroughly before the start of the investigation. Explain why it was important to wash the beetroot discs

Answer 1

To wash off any pigment

Question 2

In part 2 of this investigation you used five concentrations of alcohol. Describe a suitable control for your investigation

Answer 2

Water and two discs of beetroot

Question 3

Why would a control of water and two discs be necessary?

Answer 3

To show that the alcohol was causing the leakage of pigment / to compare it with the effects of the alcohol;

Question 4

Explain why you were instructed to shake the test tubes every minute

Answer 4

Increase the contact of all surfaces with the alcohol / prevent discs sticking together / maintain a diffusion gradient for the pigment;

Question 5

Explain why you were instructed to pour the alcohol immediately from the experimental test tube into a clean test tube

Answer 5

To make sure all the discs were in contact with alcohol for the same length of time

Question 6

You were given discs taken from fresh beetroot in your investigation. Explain why you results would have been different if you had used cooked beetroot

Answer 6

Heating/cooking would damage the membranes due to denaturing proteins

Question 7

You used a water bath in your investigation. Explain why a decrease in temperature of 5 degrees Celsius would affect the results

Answer 7

Less kinetic energy;

· Molecules move slower;

· Lower rate of diffusion;

· Membranes less fluid;

Question 8

Two students carried out the same investigation as you did. They worked in the same practical session and followed the same procedure. They worked accurately but found their results were different. Suggest one reason for this

Answer 8

Variation in beetroot

Question 9

Suggest how you can reduce the uncertainty calculated

Answer 9

(Maintain temperature) so that the rate of diffusion (of ions out of cells) remains constant

Shaking to maintain concentration gradient