beetroot CSM practical

Question 2

detailed method

Answer 2

• use extract and water to prepare a series of 6 test tubes containing 5cm3 of different concentrations of extract. concentrations should be equally spaced and cover a range from pure water to pure extract
• label the tubes 0,2,4,6,8,10
• with a second set of test tubes add 2cm3 of 100% alcohol to a test tube and put a bung in the tube.
• label the tube with alcohol concentration
• repeat for all different alcohol concentrations
• put tubes of alcohol in the water bath until temperature of alcohol reaches 30 degrees
• blot 10 discs of beetroot with a paper towel to remove excess water
• gently put the beetroot in each test tube, replace bungs straight after
• leave tubes in water bath for 5 mins. shake them gently every minute or so. then take them out
• immediately pour each solution into a clean test tube, labelled appropriately
• use colorimeter to measure absorbance and colour.
• make a calibration curve graph

Question 3

risk assessment

Answer 3

safety issues with ethanol- no naked flames, ensure good ventilation and wear eye protection

care using cork borers and scalpels

Question 4

why is it important to wash the beetroot discs

Answer 4

to wash off any excess pigment and that pigment released was from the effect of alcohol

Question 5

describe a suitable control for the investigation

Answer 5

distilled water and beetroot, to show that the alcohol was causing the leakage of pigment / to compare it with the effects of the alcohol

Question 6

why shake the tubes every minute

Answer 6

distribution of pigment, increase contact of all surfaces with alchol

Question 7

why pour the solution immediately from the test tube into the clean one

Answer 7

to limit variation in time discs are in alcohol- make sure all discs were in contact with alcohol at the same time and so no more pigment can diffuse out of the discs

Question 8

why would the results be different if we used cooked beetroot

Answer 8

cooking would damage the plasma membranes so denatures proteins and less pigment present in tissue

Question 9

why would a decrease of 5 degrees affect the results

Answer 9

less kinetic energy
molecules move slower
lower rate of diffusion
membranes less fluid

Question 10

why did students who carried out the same investigation find their results were different

Answer 10

variation in judging colour
different beetroot
different surface area of beetroot

Question 11

an alternative way of carrying out this practical is to use detergent instead of alcohol. suggest why detergent would affect the cells in a similar way to ethanol
explain why the detergent used needs to be colourless