Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
Answers to end-of-chapter questions
this is not enough to significantly change the
concentration of the cell contents; AW[3]
[Total: 20]
12a if it were diffusion, there would be (net)
movement of ions from a region of
higher concentration to a region of lower
concentration until equilibrium is reached
when concentration inside = concentration
outside; AW[1]
R because concentrations different inside
and outside
b active transport;
active transport involves pumping ions
against a concentration gradient;[2]
c if respiration is inhibited, no ATP is produced;
active transport uses ATP as energy source;
active transport stops;
diffusion continues;
ions move down concentration gradients by
diffusion until equilibrium reached; [max. 4]
[Total: 7]
Cambridge International AS and A Level Biology © Cambridge University Press 2014