A-LevelBiologyCell membranes and transportOct/Nov 2010Paper 1 Q131 Mark
The diagram shows the transport of ions across the cell surface membrane. Inside is a low concentration of sodium ions (Na+) and a high concentration of potassium Outside the cell there is a low concentration of K⁺ and a high concentration of Na*. [Figure 13.1 showing a cell membrane with carrier molecule and ion movements] The carrier molecule is a pump which exchanges Na* for K+ ions. Which ionic movements are represented by the arrows? active transport of K+ active transport of Nat diffusion of Nat diffusion of K+
A2 3 1 4
B2 3 4 1
C3 2 1 4
D3 2 4 1
✓ Correct Answer
The correct answer is A: 2 3 1 4
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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