AQA A-level BIOLOGY 7402-3 Paper 3 Mark scheme June 2026

A-level BIOLOGY 7402/3 Paper 3 Mark scheme June 2026

Question Marking Guidance Mark Comments

01.1

1. (There are) stretch-mediated sodium ion 

channels (in the membrane);

2. (Increased pressure) deforms/changes 

(sensory neurone/axon) membrane/lamella(e)

OR

(Increased pressure) deforms/changes sodium 

ion channels;

3. Sodium ion channels open;

4. Sodium ions diffuse in; 

5. Depolarisation (leading to generator potential);

3 max

(3 x 

AO1)

1. 2. 3. or 4. Accept 

Na+

Max 2 if only 

reference to sodium 

and not sodium ions

4. Accept sodium 

ions move in down 

a concentration 

gradient

5. Accept inside 

becomes positive