A student investigated the effect of pH on the digestion of protein by the stomach enzyme pepsin. The student mixed a cloudy egg-white (protein) suspension with pepsin inside test tubes containing buffer solutions at various pH levels, and recorded the time taken for the suspension to turn completely clear.
| pH of buffer solution | Time taken for protein suspension to clear (minutes) |
|---|---|
| 1.5 | 3 |
| 3.0 | 7 |
| 5.0 | 14 |
| 8.5 | Suspension remained cloudy after 30 minutes |
Explain why the protein was not digested in the tube at pH 8.5.
44 exam-style questions on AQA GCSE Biology 2.2 Animal tissues, organs and organ systems, covering 2.2.1 The human digestive system, 2.2.2 The heart and blood vessels, 2.2.3 Blood, 2.2.4 Coronary heart disease: a non-communicable disease, 2.2.5 Health issues, 2.2.6 The effect of lifestyle on some non-communicable diseases, and 2.2.7 Cancer. Each one has a worked solution and a mark scheme showing where the marks go.