Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
6 The diagram shows part of a membrane
containing a channel protein. Part of the
A
protein molecule is shaded.
a Identify the parts labelled A, B and C. [3]
B
b For each of the following, state whether
C
7 nm
the component is hydrophilic or hydrophobic:
i A ii B iii darkly shaded part of protein
iv lightly shaded part of protein. [2]
c Explain how ions would move through the channel protein. [3]
d State two features that the channel proteins and carrier proteins of membranes have in common. [2]
e State one structural difference between channel and carrier proteins. [1]
f Calculate the magnification of the drawing. Show your working. [4]
[Total: 15]
7 Copy the table below and place a tick or cross in each box as appropriate.
90
Process
diffusion
osmosis
facilitated diffusion
active transport
endocytosis and exocytosis
Uses energy in the
form of ATP
8 Copy and complete the table below to compare cell walls with cell membranes.
Uses proteins Specific Controllable by cell
[20]
Feature Cell wall Cell membrane
is the thickness normally measured in nm or μm?
location
chemical composition
permeability
function
fluid or rigid
9 A cell with a water potential of –300 kPa was placed in pure water at time zero. The rate of entry of water
into the cell was measured as the change in water potential with time. The graph shows the results of
this investigation.
[6]
Water potential / kPa
0
−300
0
Time
Describe and explain the results obtained. [8]