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02107020/CAPE/SPEC/KMS 2017
BIOLOGY
UNIT 1 – PAPER 02
KEY AND MARK SCHEME

Question 1 Specific Objectives: 1.9, 1.2, 4.4, 1.10, 1.11, 2.2, 2.3, 2.1
3.1, 3.2

(a) (i) Test Tube 1: 0.25% sucrose. It was positive for non-reducing
sugar but negative for reducing sugar and iodine
test, like Test Tube 3. However, the colour change
was less intense than Test Tube 3.

Test Tube 2: 1% glucose. It was positive for reducing sugar and
non-reducing sugar test and negative for iodine
test.

Test Tube 3: 1% glucose. It was negative for reducing sugar and
iodine, and positive for non-reducing sugar. The
colour change more intense than Test Tube 1.

Test Tube 4: Water, negative for all tests.

Test Tube 5: Starch. It was positive only for the iodine test
which means starch was present.

1 mark for each = 5 marks [5 marks]

(ii) The process of hydrolysis took place in these test tubes – 1 mark

Breaking of glycosidic bonds found in sucrose changes sucrose from
a non-reducing sugar into a reducing sugar allowing colour change
to occur because of the presence of the Benedict’s solution.
(1 mark)
[2 marks]

(b) (i) The type of inhibitor is competitive – 1 mark
[1 mark]

(ii) Primary structure: chain of polypeptide, sequence of amino acids
held together by peptide bonds.

2 marks (1 mark if no mention of peptide bonds)

Secondary structure: alpha helices and beta sheets held together
by hydrogen bonds.

2 marks (1 mark if hydrogen bonds or alpha helices or beta sheets
are missing)

Tertiary structure: three-dimensional structure, folding of
alpha helices and beta sheets into a 3-D structure or subunit
held together by hydrogen bonds, covalent bonds, ionic bonds,
disulphide bridges, van der waal forces.

2 marks (1 mark if less than 3 types of bonds are mentioned)