Cambridge International A Level Biology Revision Guide

Chapter 3: Enzymes
no inhibitor
inhibitor A
v
inhibitor B
v = velocity (rate)
[S] = substrate concentration
[S]
Copy the graphs.
a Label the graph for ‘no inhibitor’ to show the position of V max
, ½V max
and K m
. [3]
b State the effect that inhibitor A had on V max
and K m
of the enzyme. [2]
c State the effect that inhibitor B had on V max
and K m
of the enzyme. [2]
d Which inhibitor is competitive and which is non-competitive? Explain your answer. [4]
Double-reciprocal plots of the data obtained produced the following graphs.
71
1
v
X
Y
Z
0
1
[S]
e
Identify which line, X, Y or Z, corresponds to each of the following experiments:
i inhibitor absent
ii competitive inhibitor present
iii non-competitive inhibitor present
Briefly explain your answers to ii and iii. [5]
[Total: 16]