AQA A Level Biology 2021 Paper 1 Mark Scheme

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;

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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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