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. C
26. 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.
Difference : Glycogen is the major storage product of carbohydrates in
animals 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 15°C. Shirt C has the largest amount of blood
stains remaining. The enzyme must have been denatured at the high
temperature of the wash at 65°C. Shirt B does not have blood stain
remaining. The temperature of the wash at 35°C 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 the
‘lock’ 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
(ii) – Inference 1 : pH 2 is not suitable for amylase actions. Therefore
starch is not hydrolysed and dark blue remains.
– Inference 2 : pH 7 is suitable for amylase action. Therefore starch
is hydrolysed and the colour of iodine change from
dark blue to brown.
(c) Enzyme act optimally at its pH.
(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 a
neutral 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 60°C, 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.
1 (a) (i) Observation 1 : At pH 2, the colour of the iodine remains dark blue after
10 minute.
Observation 2 : At pH 7, the colour of iodine remains dark blue until the
second minute.
(ii) – Inference 1 : pH 2 is not suitable for amylase actions. Therefore
starch is not hydrolysed and dark blue remains. – Inference 2 : pH 7 is suitable for amylase action. Therefore starch
is hydrolysed and the colour of iodine change from
dark blue to brown.
(c) Enzyme act optimally at its pH.
(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 a
neutral 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 60°C, 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.
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 37°C. (40°C experimentally)
Manipulated : Temperature
Responding : Rate of reaction
Constant : Amylase, pH, starch
Materials : 2% starch solution, salivary solution, ice cubes, distilled
water and iodine solution.
Apparatus : Dropper, stopwatch, large beaker, small beaker, test tubes,
thermometer, white tile, Bunsen burner, tripod stand, test tube
rack 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.
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 poured
into test tube A and B respectively.
6. Test tubes A, B and C is immersed in a water bath at 20°C 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
30°C, 40°C, 50°C and 60°C.
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
optimum temperature (40°C). The hypothesis is accepted
