CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: WORKBOOK
Exam-style questions and sample answers have been written by the authors. In examinations, the way marks are awarded
may be different.
Workbook answers
Chapter 3
2
Exam-style questions
1
atake samples of the reacting mixture at set
time intervals ; add iodine solution ; note
the depth of blue-black colour using a
colorimeter / colour standards ; the more
quickly the blue-black colour disappears
the greater the rate of activity ; [max 3]
b
c
bdiffuses into the blood (from the
stomach) ; dissolves in blood plasma ;
transported to lungs in named blood
vessels ; diffuses from blood into alveoli
(and is breathed out) ;
[max 3]
cchange in 13CO2 always higher for A than
B ; A reaches peak of 21 a.u. but B never
above 0 ; A rises until 20 minutes then
falls but B oscillates / falls throughout ;
[max 2]
ioptimum pH is about 5.2 to 5.4, where
activity of the amylase is about 152
arbitrary units ; activity is 0 at pH 3
and pH 10 ;
[2]
iidecreases or increases of pH below
or above the optimum affect the
hydrogen and ionic bonds ; so the
shape of the active site is lost and the
enzyme can no longer bind with its
substrate ; the further the pH is from
the optimum, the more bonds are
broken and the more the shape is lost ;
[3]
dthis is a non-invasive procedure / quick
and easy to do ;
[1]
3
ias temperature increases, the rate of
activity of the enzyme increases ; the
fastest rate of reaction occurs at a
temperature of 90 °C ; temperature
appears to affect the optimum pH,
which is lower at a temperature of
37 °C than at 90 °C ;
[max 2]
cusing immobilised pectinase allows
treatment of the fruit / fruit juice, to take
place at higher temperatures ; could mean
that juice, extraction / clarification, takes
place faster (because higher temperatures
can be used) ;
[2]
carry out the reaction at a constant
pH of 5.5 ; at a range of temperatures
from about 80 to 100 °C ; a suitable
interval would be 2 °C / experiments
would be carried out at 80, 82, 84 °C
and so on ; do three repeats for each
temperature ;
[max 3]
denzyme can be reused many times
(reducing costs of purchasing enzyme) ;
no contamination of product with the
enzyme (reducing costs of purification) ;
(ignore references to cost alone)
[2]
[Total: 13]
1
[Total: 7]
aactivity of immobilised pectinase always
higher than that of free pectinase ;
immobilised falls to minimum of 44%
of activity before heating, but free falls
to 0 ; immobilised still has activity after
being exposed heated for 60 minutes, but
free has no activity after 30 minutes ;
use of manipulated comparative figures,
for example, after 10 minutes activity of
immobilised enzyme is 1.6 times greater
than that of free enzyme ;
[max 3]
btemperature (of the reacting mixture) ;
concentration of enzyme ; concentration
of substrate ; pH ;
[max 2]
ii(The optimum temperature must be
somewhere around 90 °C. )
athis distinguishes it from CO2 that has not
been produced by urease activity ;
[1]
[Total: 9]
Cambridge International AS & A Level Biology – Jones & Parkin © Cambridge University Press 2020