A-LevelBiologyCell membranes and transportFeb/Mar 2024Paper 1 Q191 Mark
Agar cubes can be used to demonstrate the effect on diffusion of changing the surface area to volume ratio. Three different agar cubes made using a coloured indicator solution were placed into a dilute acid that diffused into the cubes. As the acid diffused into the agar cubes, the colour of the indicator solution changed. The cubes had volumes of 1 cm³, 2 cm³ and 3 cm³ and were left in the dilute acid for 10 minutes. All other variables were kept the same. After 10 minutes, the agar cubes were removed from the dilute acid and cut in half. The cut surfaces were observed and the results were recorded as diagrams. All diagrams were drawn to the same scale. The results for the 2 cm³ cube are shown. [Figure 19.1] Which diagrams show the results for the 1 cm³ and the 3 cm³ cubes?
A1 cm³ cube showing large diffused area; 3 cm³ cube showing small diffused area
B1 cm³ cube showing small diffused area; 3 cm³ cube showing large diffused area
C1 cm³ cube showing almost complete diffusion, very small original colour area; 3 cm³ cube showing very small diffused area, very large original colour area
D1 cm³ cube showing complete diffusion; 3 cm³ cube showing small diffused area
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The correct answer is C. This question tests the candidate's understanding of cell membranes and transport within the Biologysyllabus. The examiner's mark scheme requires...
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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...
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