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A-LevelBiologyCell membranes and transportOct/Nov 2025Paper 2 Q17 Marks

Many substances can move through cell surface membranes between the cytoplasm of animal cells and the extracellular environment. (a) A student made a drawing to summarise the movement of substances across the cell surface membranes of mammalian red blood cells. Fig. 1.1 shows the drawing made by the student: Each arrow indicates the movement of a substance through the membrane. The number of each of the 4 shapes represents the relative concentrations of each substance in the cytoplasm and in the blood plasma. The student carried out research and made a list of some of the substances found in red blood cells as shown in Fig. 1.2. Table 1.1 shows information about the 4 types of movement of substances across the cell surface membranes of red blood cells as shown in Fig. 1.1. Complete Table 1.1 using the information in Fig. 1.1 and Fig. 1.2. Table 1.1 letter from Fig. 1.1 | type of movement | name of part of membrane involved | example of a substance that moves across the membrane (from Fig. 1.2) --- | --- | --- | --- A | simple diffusion | phospholipids | B | facilitated diffusion | | calcium ions C | facilitated diffusion | | D | | |

📋 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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About This A-Level Biology Question

Topic

This structured question tests Cell membranes and transport in A-Level Biology (syllabus code 9700). It is worth 7 marks.

Source

This question appeared in the Cambridge A-Level Biology Oct/Nov 2025 examination, Paper 2 Variant 3.

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