Page 147 - SUBSEC October 2017_Neat

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

Question 1 cont’d

Quaternary structure: multiple subunits or tertiary structures
coming together to make a functional protein 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)

Any 3 levels = 6 marks
[6 marks]

(iii) Prokaryotic – Cell 1
Eukaryotic – Cell 2

1 mark for both correct [1 mark]

(iv) Ribosomes: site of protein synthesis

Golgi apparatus: involved in packaging of substances for
transport in the cell, modifies substances from the endoplasmic
reticulum

Rough endoplasmic reticulum: protein synthesis

1 mark each = 3 marks
[3 marks]

(c) Fluid mosaic model

1. Structure of the cell membrane is a bilayer of phospholipids
whose orientation results in a layer of hydrophobicity
between regions of hydrophilic interactions (1) and includes
glycolipids, cholesterol, protein, glycoprotein (1) and its
fluidity, allowing movement of components (1).

2. Given the fact that water, potassium ions and glucose are all
polar molecules, they cannot simply diffuse through the
membrane due to the hydrophobic region. (1)

3. Therefore, there is a need for proteins (1) whether as pumps,
channels or carrier proteins within the membrane to aid with
transport of these molecules into the cell (1)

4. Water is moving from an area of high potential to an area of low
potential, thus it will move via passive transport, in particular
osmosis (1), and to facilitate this a protein channel is needed
aquaporin. (1)