AQA A Level Biology 2021 Paper 1 Mark Scheme
Question Marking Guidance Mark Comments
01.1 1. Substrate binds to the active site/enzyme
OR
Enzyme-substrate complex forms;
2. Active site changes shape (slightly) so it is
complementary to substrate
OR
Active site changes shape (slightly) so
distorting/breaking/forming bonds in the
substrate;
3. Reduces activation energy;
3
1. Accept for ‘binds’,
fits
Question Marking Guidance Mark Comments
01.2 Adenosine diphosphate; 1
Question Marking Guidance Mark Comments
01.3 Mark in pairs, 1 and 2 OR 3 and 4 OR 5 and 6
1. Boil
OR
Add (strong) acid/alkali;
2. Denatures the enzyme/ATP synthase;
OR
3. Put in ice/fridge/freezer;
4. Lower kinetic energy so no enzyme-substrate
complexes form;
OR
5. Add high concentration of inhibitor;
6. Enzyme-substrate complexes do not form;
2
1. Accept heat at >
50oC OR at very
high temperatures
2. Accept for
'denatures', a
description of
denaturation
4. Accept ES for
enzyme substrate
complex
MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021
6
Question Marking Guidance Mark Comments
01.4 1. (With) increasing Pi concentration, more
enzyme-substrate complexes are formed;
2. At or above 40 (mmol dm-3
) all active sites
occupied
OR
At or above 40 (mmol dm-3
) enzyme
concentration is a limiting factor;
2
MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021
7
Question Marking Guidance Mark Comments
02.1 1. Large(r) organisms have a small(er) surface
area:volume (ratio);
OR
Small(er) organisms have a large(r) surface
area:volume (ratio);
2. Overcomes long diffusion pathway
OR
Faster diffusion;
2
2.Accept short
diffusion pathway
2. Accept for ‘faster’,
more
Question Marking Guidance Mark Comments
02.2 Mark in pairs, 1, and 2 OR 3. and 4.
1. Water has low(er) oxygen partial
pressure/concentration (than air);
2. So (system on outside) gives large surface area
(in contact with water)
OR
So (system on outside) reduces diffusion
distance (between water and blood);
3. Water is dense(r) (than air);
4. (So) water supports the systems/gills;
Category | AQA Questions and Marking Scheme |
Authors | Qwivy.com |
Pages | 22 |
Language | English |
Tags | AQA A Level Biology 2021 Paper 1 Mark Scheme |
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