AQA A LEVEL BIOLOGY Paper 2 MS 2021.

AQA A LEVEL BIOLOGY Paper 2 MS 2021. MARK SCHEME − A-LEVEL BIOLOGY − 7402/2 − JUNE 2021 Question Marking Guidance Mark Comments 1. Phosphorylation based on glucose using ATP; 2. Oxidation based on triose phosphate to pyruvate; Accept all mark points within diagrams. 3. Net gain based on ATP; 4. NAD reduced; 2. Accept removal based on hydrogen from triosephosphate for oxidation. 01.1 4 max 3. Accept any description that indicates a net gain e.g., 4 produced, 2 used. 4. Accept NADH/NADH2/NAD H + 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. 4 Downloaded by: nurse001 | Distribution of this document is illegal S - The Marketplace to Buy and Sell your Study Material MARK SCHEME − A-LEVEL BIOLOGY − 7402/2 − JUNE 2021 Question Marking Guidance Mark Comments 1. Higher concentration based on potassium ions inside and higher concentration based on 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; 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). 02.1 3 1, 2 and 3 reference to ions or Na+ and K + isrequired. If mentioned once allow for all mark points. 1, 2 and 3. If an answer provides two or three based on these mark points without any reference to ions – award one maximum mark. 3. Accept 3 Na+ out and 2 K + within but reject if numbers used are incorrect.