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?
✓ Correct Answer
The correct answer is C: [Graph C showing rate of starch digestion by amylase /mg min⁻¹ against pH]
📋 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.
Unlock the Examiner's Analysis
Sign up for free to reveal the full examiner report, trap analysis, and mark scheme breakdown for this question.
Sign Up Free to Unlock →Join thousands of Cambridge students already using Oracle Prep