AQA A Level Biology Paper 2 2021 Mark Scheme
Question Marking Guidance Mark Comments
01.1
1. Phosphorylation of glucose using ATP;
2. Oxidation of triose phosphate to pyruvate;
3. Net gain of ATP;
4. NAD reduced;
4 max
Accept all mark points
in diagrams.
2. Accept removal of
hydrogen from triose
phosphate for
oxidation.
3. Accept any
description that
indicates a net gain
e.g., 4 produced, 2
used.
4. Accept
NADH/NADH2/NADH
+ H+
produced.
Question Marking Guidance Mark Comments
01.2
1. Less/no reduced NAD/coenzymes
OR
Fewer/no hydrogens/electrons removed (and
passed to electron transfer chain);
2. Oxygen is the final/terminal (electron) acceptor;
2
1. Accept less/no FAD
reduced.
MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2021
5
Question Marking Guidance Mark Comments
02.1
1. Higher concentration of potassium ions inside
and higher concentration of sodium ions outside
(the neurone)
OR
potassium ions diffuse out
OR
sodium ions diffuse in;
2. (Membrane) more permeable to potassium ions
(leaving than sodium ions entering)
OR
(Membrane) less permeable to sodium ions
(entering than potassium ions leaving);
3. Sodium ions (actively) transported out and
potassium ions in; 3
1. Accept ‘more’ for
‘higher concentration’.
1. Accept ‘sodium
ions can’t diffuse in
(due to alternative
explanation).
2. Accept for ‘less
permeable to sodium
ions’ is ‘impermeable
to sodium ions’ or
‘sodium
gates/channels are
closed’ (alternative
explanation).
1, 2 and 3 reference
to ions or Na+
and K+
is required. If
mentioned once allow
for all mark points.
1, 2 and 3. If an
answer provides two
or three of these mark
points without any
reference to ions –
award one maximum
mark.
3. Accept 3 Na+
out
and 2 K
+
in but reject
if numbers used are
incorrect.
Question Marking Guidance Mark Comments
02.2
1. Myelination provides (electrical) insulation;
2. (In myelinated) saltatory (conduction)
OR
(In myelinated) depolarisation at nodes (of
Ranvier);
3. In non-myelinated depolarisation occurs along
whole/length (of axon);
3
1. Reject thermal
insulation.
1. Accept description of
(electrical) insulation.
3. Accept action potentials
for depolarisation.
2 and 3. ‘Messages’ or
‘signals’ disqualifies first of
these marks credited.
MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2021
6
Question Marking Guidance Mark Comments
02.3
1. No/less ATP produced;
2. No/less active transport
OR
Sodium/potassium pump inhibited;
3. Electrochemical gradient not maintained
OR
(Facilitated) diffusion of ions causes change to
0 mV
OR
(Results in) same concentration of (sodium and
potassium) ions (either side of membrane)
OR
No net movement of (sodium and potassium)
ions;
3
2. Accept Na+
not/fewer moved out
and K+ not/fewer
moved in.
3. Accept reaches
electrical
equilibrium/balance.
3. Accept
concentration gradient
of sodium and
potassium ions not
maintained
Category | AQA Questions and Marking Scheme |
Authors | Qwivy.com |
Pages | 16 |
Language | English |
Tags | AQA A Level Biology Paper 2 2021 Mark Scheme |
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