CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: COURSEBOOK
Exam-style questions and sample answers have been written by the authors. In examinations, the way marks are awarded
may be different.
Coursebook answers
Chapter 11
Exam-style questions
1
C ;
[1]
2
D ;
[1]
3
D ;
[1]
4
A ;
[1]
5
B ;
[1]
6
R = reject. This indicates a possible answer that
should be rejected.
ared blood cells, become ‘worn out’ / do
not live long / last for approx. 120 days ;
misshapen / damaged, red blood cells can
block capillaries ;
; The bold semicolon indicates the award of
1 mark.
material in red blood cells can be, reused /
recycled ;
/ This indicates an alternative answer for the same
mark. The alternatives may be separated from the
rest of the answer by commas.
e.g. amino acids from, haemoglobin /
other named protein, can be used to make
new proteins ;
( ) Text in brackets is not required for the mark.
e.g. iron in haem groups (of haemoglobin)
used to make new haem groups ;
The mark schemes, suggested answers and
comments that appear here were written by the
author(s). In examinations, the way marks would
be awarded to answers like these may be different.
Notes about mark schemes
A or accept indicates an alternative acceptable
answer.
Underlining This is used to indicate essential
word(s) that must be used to get the mark.
e.g. phospholipids used to make new
cellular membranes ;
AW means ‘alternative wording’. It is used to
indicate that a different wording is acceptable
provided the essential meaning is the same, and is
used where students’ responses are likely to vary
more than usual.
AVP ;
bred blood cells attach to surface of
macrophage ;
endocytosis / phagocytosis ;
AVP means ‘additional valid point’. This means
accept any additional points given by the student
that are not in the mark scheme, provided they
are relevant. But accept only as many additional
points as indicated by the bold semicolons, e.g.
AVP ; ; means award a maximum of 2 extra marks.
cell surface membrane infolds / cytoplasm
extends around red blood cell (as at top of
the TEM) ;
membrane fusion to form a (phagocytic)
vacuole ;
ORA means ‘or reverse argument’ and is used
when the same idea could be expressed in the
reverse way. For example: ‘activity increases
between pH2 and pH5 ORA’ means accept
‘activity decreases between pH5 and pH2’.
red blood cell is enclosed in a vacuole ;
lysosomes fuse with vacuole ;
(lysosomal) enzymes released into vacuole ;
proteases breaks down (named) protein(s) ;
max. This indicates the maximum number of
marks that can be given.
lipases break down phospholipids ;
AVP ;
1
[max. 3]
[max. 6]
[Total: 9]
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CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: COURSEBOOK
7
a
c
Experiment 1
30−40% of phagocytic cells (both
neutrophils and macrophages) did not
take up any fungal cells ;
very few phagocytic cells took up more
than four fungal cells ;
no phagocytic cells took up more than six
fungal cells ;
e ach antibody is specific to an
antigen ; ii
fewer phagocytic cells did not take up any
fungal cells (than in Experiment 1) ;
15% of macrophages and 30% of
neutrophils did not take up any fungal
cells ;
more phagocytic cells took up 4 fungal
cells (than in Experiment 1) ;
more phagocytic cells took up more than
4 fungal cells (than in Experiment 1) ;
AVP ; ;
[max. 5]
a ll the antigens that the immune
system recognises as foreign ; [max. 1]
d
is specific to an antigen on tetanus
bacteria ;
responds quickly to another infection by,
pathogen with same antigen / same (strain
of) pathogen ;
e.g. if no antibodies to coat pathogen to
facilitate endocytosis ;
as there are a large number / there is a
large clone ;
ratios between pathogen and phagocytes
may be different (i.e. not 1 : 1 or 3 : 1) ;
during secondary immune response ;
cells were left for only six hours ;
differentiate into plasma cells ;
phagocytes may need much longer than
this to start carrying out endocytosis ;
this may be responsible for large number
of phagocytes that did not take up any
fungal cells ;
[max. 3]
[Total: 8]
to give large number of antibody
molecules in short space of time ; [max. 3]
9
[Total: 13]
a
phagocyte has
a lobed nucleus ;
lysosomes ;
larger quantity of cytoplasm ;
stem cells:
divide repeatedly (by mitosis) ;
for replacement of, (white) blood cells /
lymphocytes ;
[2]
b
cell H is a memory cell ;
remains in, circulation / lymph system /
body ;
e.g. if no cytokines from T-lymphocytes
to stimulate endocytosis ;
a
[max. 1]
n
on-self refers to antigen(s) that are
not in a person’s body (e.g. those of,
pathogens / the ABO system that they
do not have) ;
behaviour of cells in culture may be
different ;
s elf refers to antigen(s) within a
person’s body (e.g. those of the ABO
blood group system which they have) ;
cells are not in their normal environment
in the body / AW ;
AVP ; ;
[3]
a ll the antigens that the immune
system does not recognise as
foreign ;
bthese are the results of an experiment with
cells in isolation ;
2
a ntigen refers to any substance
that stimulates the production of
antibodies ;
a ntibodies are proteins produced
by, plasma cells / (activated)
B-lymphocytes ;
Experiment 2
8
i
i
mitosis ; [1]
ii
plasma cell ; [1]
iii
antibody ; A immunoglobulin
[1]
cytoplasm with granules / granular
cytoplasm ;
[3]
b presentation of antigen(s) by,
macrophages / (other) APCs ;
some T-lymphocytes have receptors
complementary to antigen ;
these are selected ;
Cambridge International AS & A Level Biology © Cambridge University Press 2020
CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: COURSEBOOK
some children may not receive boosters ;
divide by mitosis ;
AVP ;
T-helper lymphocytes secrete cytokines ;
to activate B-lymphocytes ;
T-killer lymphocytes search for cells
infected by, parasite / pathogen ;
without involvement of macrophages ;
B-lymphocytes differentiate into plasma
cells ;
secrete antibodies (T-lymphocytes do not
secrete antibodies) ; [max. 2]
[Total: 11]
immunity is gained by the transfer
of antibodies from, mother’s blood
during pregnancy / another source ;
no immune response within the body ;
natural passive immunity:
b
[2]
baby has passive immunity ;
antibodies against measles antigens (from
mother) will interact with, measles
viruses / antigens, in vaccine ;
so prevent an immune response ;
therefore no memory cells will be
formed ;
[max. 3]
c
some suggestions:
difficulty in reaching nearly 100% global
coverage ;
some populations difficult to reach ;
any reason, e.g. living in inaccessible /
dangerous, places ;
some children may not respond to the
vaccine ;
3
[1]
transcription (of DNA) ;
assembly of amino acids to make each of
the four polypeptides ;
assembly of polypeptides to make
antibody molecule ;
addition of sugar chains (to make
glycoprotein) / glycosylation ;
antibody molecules packaged in Golgi
body into vesicles ;
release of antibodies by exocytosis ;
[max. 4]
c variable region(s) are antigen-binding sites ;
variable regions, are specific /
complementary, to antigen ;
variable regions have different amino acid
sequences for different antigens ;
20 different amino acids can be arranged
to form different shapes ;
antibodies cross the placenta ;
in, breast milk / colostrum ;
disulfide ; the two variable regions (on IgG
molecules) are identical ;
antigen(s) / pathogen(s), have not
entered the body ;
[max. 2]
ii
i
translation (of mRNA) ;
c B-lymphocytes can be activated by
presence of, antigen / pathogen, alone ;
i
X
= variable region / antigen-binding
site ;
Y = constant region ; [2]
b
prevent reproduction of, virus / pathogen ;
[max. 6]
10 a
11 a
ii
T-killer lymphocytes destroy host cells
(and pathogen / and measles virus) ;
[Total: 10]
selected B-lymphocytes divide and
differentiate into plasma cells that secrete
antibodies ;
[max. 3]
disulfide bonds hold polypeptides together ;
hinge region allows flexibility in binding
to antigen ;
constant region for binding to receptors
on phagocytes ;
[max. 4]
dmonoclonal antibodies used in diagnosing
a condition all have the same specificity ;
each monoclonal antibody detects only
one antigen ;
monoclonals can be used to distinguish
between different, pathogens / strains of
pathogens ;
monoclonals can be, labelled / tagged,
with flourescent labels / radioactive labels ;
can locate position of, cancers / infection
by pathogens / blood clots ;
diagnosis can be much fast(er) than by
other methods ;
Cambridge International AS & A Level Biology © Cambridge University Press 2020
CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: COURSEBOOK
comparison with any other method ;
ii emits gamma rays, which pass through
soft tissue and so can be detected from
outside the body ;
e.g. growing pathogen in culture ;
can detect pathogens that do not grow in
culture ;
weak gamma rays, reducing chance of
mutation ;
can be used to detect concentrations of,
antibodies / cells ;
short half-life, so no continuing source
of gamma rays ;
any e.g. ; HIV particles / antibodies to HIV
AVP ;
indium has no biological role ; [max. 3]
[max. 4]
iii a dd, a drug / an enzyme to activate a
drug, to kill cancer cells ;
[Total: 15]
12 a
2 ; 5 ; 3 ; 1 ; and 4 ;
b i
[1]
inds only with tumour-associated
b
antigen (TAG) glycoprotein in cancer
cells ;
in place of radioactive label ;
[2]
[Total: 9]
source of gamma rays concentrated
by cancer ;
gamma rays can be detected from
outside the body ; 4
[3]
Cambridge International AS & A Level Biology © Cambridge University Press 2020