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Biology · Enzymes · Effect of pH
Effect of pH on amylase
Five tubes, each buffered to a different pH (3, 5, 7, 9, 11), all held at 35 °C. Equal amylase and starch. Sample every 30 s and test with iodine on a white tile. Time to clear → rate of digestion.
t = 0 s
Results table
| pH | t (s) | rate × 1000 |
|---|---|---|
| pH 3 | — | — |
| pH 5 | — | — |
| pH 7 | — | — |
| pH 9 | — | — |
| pH 11 | — | — |
Exam-style questions
1. At which pH was the rate highest?
2. Why is amylase still ACTIVE — just slower — at pH 5 and pH 9, but barely active at pH 3 and pH 11?
3. Why keep temperature constant?
4. Salivary amylase optimum is pH 7; pepsin optimum is pH 2. Why?