Name: _______________________________________________ 	

  	
  	
Topic 2 Genes & Health	
 
Cell membrane permeability, Enzyme reaction
 	
Date:	

  	
  	
Time: 35 minutes 	
  	
Total marks available: 32 	
  	
Total marks achieved: ______ 	

  	

  	

  	

  	

  	

  	

  	
Practical skill focus 	

	

Questions

Q1.
 
The cell vacuoles of beetroot (Beta vulgaris) contain the red pigment betalain.
A student investigated the effect of temperature on the permeability of beetroot cell membranes.
In this investigation, five pieces of beetroot were used. One piece of beetroot was left in 10 cm3 of distilled water for
20 minutes at 20 °C.
After 20 minutes, the piece of beetroot was removed and the intensity of the colour of the water was measured using a colorimeter.
This was repeated with the other pieces of beetroot using water temperatures of 40 °C, 60 °C, 80 °C and 90 °C.
(a)  The student's results are shown in the graph below.

(i)  Using the information in the graph, describe the effect of temperature on the permeability of the cell membranes.
(2)
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(ii)  Using the information in the graph and your knowledge of membrane structure, explain the effect of temperature on the cell membranes.
(3)
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*(b)  Using all the information given in the question, describe how this investigation could be carried out to provide valid and reliable results.
(5)
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(Total for question = 10 marks

Q2.
 
Catalase is an enzyme present in many tissues of most living organisms, but can be found in high concentrations in liver cells. Its role is to break hydrogen peroxide down into oxygen and water. Hydrogen peroxide is produced by cells and is very harmful if it is not broken down.
A student carried out an investigation into the action of catalase. Some liver was chopped into small pieces, and added to hydrogen peroxide. The volume of oxygen gas produced was recorded and a graph was drawn.

(i)   Calculate the initial rate of reaction.
(3)

Answer ...........................................................

(ii)   Analyse the graph to explain the change in the total volume of oxygen produced over the course of reaction.
(4)
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(iii)   Draw on the graph the line you would expect if the student repeated the investigation with the same concentration of hydrogen peroxide but with double the mass of liver.
(2)
  
(Total for question = 9 marks)

Q3.
 
The cell vacuoles of beetroot (Beta vulgaris) contain the red pigment betalain.
A student investigated the effect of ethanol on the permeability of beetroot cell membranes. 
In this investigation, 10 identical pieces were cut from one beetroot. One piece of beetroot was left in
10 cm3 of 30% ethanol for 20 minutes at 20 °C.
After 20 minutes, the piece of beetroot was removed and the intensity of the colour of the ethanol solution was measured using a colorimeter.
This was repeated with other pieces of beetroot that were left in ethanol concentrations of 0%, 50%, 70% and 100%, at 20 °C.
The student repeated this investigation with the other five pieces of beetroot at the same temperature of 20 °C. The graph below shows the results of these investigations.

(a)  Using the information in the graph, describe the effect of ethanol concentration on the intensity of colour.
(3)
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(b)  Using the information in the graph and your knowledge of membrane structure, explain the effect of ethanol on the permeability of beetroot cell membranes.
(4)
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(c)  Suggest why the results for these two investigations are different.
(2)
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(Total for question = 9 marks)

Q4.
 
Spiders inject a mixture of digestive enzymes into the body of their prey and feed on the products of this digestion.
The photograph shows a spider with its prey.

The effect of substrate concentration on the rate of an enzyme reaction was investigated.
Two substrate solutions, A and B, were used. Solution A had a higher concentration than solution B. The optimum pH for the enzyme was pH 7.
The product lowered the pH of the solution.
The rate of reaction was determined at 1-minute intervals for 10 minutes.
The graph shows the results of this investigation.

It was concluded that the product reduces the activity of the enzyme.
Comment on the validity of this conclusion.
(4)
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(Total for question = 4 marks)