A-LevelBiologyEnzymesOct/Nov 2025Paper 1 Q151 Mark
Some students investigated the effect of pH on the rate of starch digestion by amylase at 20 °C. • They added 2 cm³ of a 1% amylase solution and 1 cm³ of pH 4 buffer to a test-tube. • They added 2 cm³ of a starch solution, containing 0.02 g of starch, to the test-tube. • They measured the time taken for the starch to be digested (to disappear). The students then repeated these steps with pH 5, pH 6, pH 7 and pH 8 buffers. The table shows the results. [Table with columns 'pH' and 'time taken for starch to be digested / minutes' and rows 4: 4.0, 5: 1.5, 6: 1.0, 7: 2.5, 8: 6.0] Which graph is correct for these data?
A[Graph A showing rate of starch digestion by amylase /minutes against pH]
B[Graph B showing rate of starch digestion by amylase /seconds against pH]
C[Graph C showing rate of starch digestion by amylase /mg min⁻¹ against pH]
D[Graph D showing rate of starch digestion by amylase /mg s⁻¹ against pH]
✓ Correct Answer
The correct answer is C. This question tests the candidate's understanding of enzymes within the Biologysyllabus. The examiner's mark scheme requires...
📋 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...
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