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Paper 1

1. C 2. D 3. B 4. C 5. A

6. C 7. A 8. D 9. B 10. C

11. A 12. D 13. A 14.B 15. D

16. A 17. D 18. D 19. D 20. D

21. A 22. C 23.A 24. B 25. C26. A 27. C 28. C 29. B 30. C

31. A

Paper 2

Section A

1 (a) U : Enzyme V : Substrate

W : Enzyme-substrate complex

X : Product

(b) U : Maltase V : Maltose

X : Glucose (c) Lock : Enzyme

Key : Substrate

(d) Temperature / pH / Substrate concentration / Enzyme concentration

2(a) (i) X : Monosaccharides Y : Disaccharides

Z : Polysaccharides

(b) Similarity : Both are major storage products of carbohydrates.

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Difference : Glycogen is the major storage product of carbohydrates inanimals while starch is the major storage product of carbohydrates in plants.

Section B

3 (a) (i) Protease enzyme. Shirt A has a considerable amount of stains as

enzyme is less active at 15C. Shirt C has the largest amount of bloodstains remaining. The enzyme must have been denatured at the high

temperature of the wash at 65C. Shirt B does not have blood stain

remaining. The temperature of the wash at 35C must be at the optimum

temperature of the enzyme to digest most of the blood stains efficiently.

(ii) The protease enzyme in the washing powder will act on the blood stains

which contain protein and removes blood stains from the shirt.

(iii) Lipase

(b) Enzymes are highly specifi c in action.

Enzymes are made up of protein. Enzymes speed up the rate of biochemical reactions but remain

unchanged at the end of reaction.

(d) In the lock and key hypothesis, the enzyme molecule represents thelock while the substrate molecule represents the key.

An enzyme-substrate complex formed when the substrate molecule

binds to the active site of the enzyme molecule.

Products formed after the enzyme catalyses the substrate, then leave

the active site.

The enzyme molecule is free to bind other substrate molecules.

Paper 3

1 (a) (i) Observation 1 : At pH 2, the colour of the iodine remains dark blue after10 minute.

Observation 2 : At pH 7, the colour of iodine remains dark blue until the

second minute.

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(ii) Inference 1 : pH 2 is not suitable for amylase actions. Thereforestarch is not hydrolysed and dark blue remains.

Inference 2 : pH 7 is suitable for amylase action. Therefore starchis hydrolysed and the colour of iodine change from

dark blue to brown.

(c) Enzyme act optimally at its pH.

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(f) 1. The rate of amylase reaction is very low in an acidic medium.

2. The rate of amylase reaction is very high or at the maximum rate in aneutral medium.

3. The rate of amylase reaction is very low in an alkaline medium.

(g) The colour of the blue-dark iodine solution does not change to brown.

This is because at 60C, the amylase denatures. Therefore the substrate

which is starch could not be change to its simple product.

(h) The rate of enzyme reaction is highest at the optimum pH.

(i) Optimum pH is pH neutral whereby amylase reaction is very high or at

the maximum rate.

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2. Aim: To study the effect of temperature on the activity of enzyme

amylase.

Problem Statement : At what temperature does enzyme amylase

function most efficiently?

Hypothesis : Enzyme amylase achieves its optimum rate of reaction

at 37C. (40C experimentally)

Manipulated : Temperature

Responding : Rate of reaction

Constant : Amylase, pH, starch

Materials : 2% starch solution, salivary solution, ice cubes, distilledwater and iodine solution.

Apparatus : Dropper, stopwatch, large beaker, small beaker, test tubes,

thermometer, white tile, Bunsen burner, tripod stand, test tuberack and wire gauze.

Technique : Testing for the presence of starch and recording the time

taken for the hydrolysis of starch by salivary amylase to

complete.

Procedure :

1. 3 ml of saliva is collected in a small beaker.

2. The same amount of distilled water is added into the small beaker to produce

a salivary solution.

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3. Three test tubes is labelled as A, B and C.4. A drop of iodine solution is put into all the cavities of a white tile.

5. 1 ml of salivary solution and 10 ml of 2% starch solution is pouredinto test tube A and B respectively.

6. Test tubes A, B and C is immersed in a water bath at 20C for 5 minutes.

7. The contents of test tube A and B is poured into test tube C, and the

Stopwatch is started.8. Dropper is used to transfer a drop of mixture from test tube C into a

cavity of the white tile.

9. Steps 8 is repeated at one-minute intervals until the blue-black colour of the

iodine solution disappears.

10. The time taken for the blue-black colour to disappear is recorded in a table

11. A new set of three test tubes is used to repeat steps 3 10 for temperatures of

30C, 40C, 50C and 60C.

12. The rate of reaction of amylase is calculated by using 1t, where t=

time taken for the blue-black colour disappears.

Conclusion: The results shows that rate of reaction of amylase achieve maximum rate at

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optimum temperature (40C). The hypothesis is accepted.