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2 marksNutrition in Living Organisms

CSEC Biology · January 2005 · Paper 2 · Question 1(a)

An experiment was set up to investigate how the rate of reaction of an enzyme from the human digestive system varies with temperature. Five different temperatures were investigated, each tube containing 4 drops of enzyme solution and 4 cm³ of starch solution. A white tile was prepared with drops of iodine. One drop of the mixture from each tube was removed at intervals and added to a drop of iodine on the tile every minute for ten minutes. The results are shown by blackened and non-blackened circles.

Complete the key beside Figure 1b to indicate the colours represented by the blackened and non-blackened circles.

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Other parts of this question

  1. 1(b)(i)Explain why the colour of the drops remained the same for the 10 minutes in row A and row E.[4 marks]
  2. 1(b)(ii)What substance would you expect to find in Tube D after 2 minutes?[1 mark]
  3. 1(b)(iii)Describe the test that could be carried out to find out if you were correct at (b)(ii) above.[2 marks]
  4. 1(c)(i)Using information from the experiment in Figures 1a and 1b, complete the graph below to show the effect of temperature on the time taken for the reaction…[3 marks]
  5. 1(c)(ii)At what temperature did the reaction take place most rapidly?[1 mark]
  6. 1(c)(iii)What would you expect to happen if, at the end of the 10-minute period, the contents of Tubes A and E were brought to 30°C and then tested with iodine? Give…[4 marks]
  7. 1(d)(i)Use the information on page 2 to describe the procedure used to set up this investigation, by placing each step in the correct order in which it should be…[5 marks]
  8. 1(d)(ii)Explain the importance of stirring the mixture.[1 mark]
  9. 1(e)(i)How should the cotyledons be prepared for testing?[1 mark]
  10. 1(e)(ii)Explain what happens to the starch stored in the cotyledons when the seed germinates.[3 marks]
  11. 1(f)(i)Explain the appearance of the seedlings in Figure 1c.[2 marks]
  12. 1(f)(ii)If you are asked to set up an investigation in a laboratory to show that your explanation in (f)(i) is correct and all you have is an old shoe box, how would…[1 mark]

More practice: the rest of this paper · more Nutrition in Living Organisms questions · all CSEC Biology past papers