CAIE IGCSE Biology 5.1.9 pH & Enzyme Activity
Practise reading optimum pH from activity curves and explaining how unsuitable pH alters or denatures the active site, preventing complementary substrate binding.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Exam points
- read an enzyme's optimum pH from the maximum reaction rate or percentage activity on a graph
- explain that unsuitable pH changes or denatures the active site so its substrate no longer fits
- apply pH effects to amylase in the acidic stomach and neutralised conditions of the small intestine
5.1.9—Effect of changes in pH on enzyme question 1
[Maximum number: 6]
Explain why amylase digests starch in the small intestine but does not digest starch in the stomach.
any six from:
1 stomach produces, gastric juice / hydrochloric acid / HCl ;
2 acidic / low pH, in stomach ;
3 (acid) denatures, amylase / enzyme ;
4 changes shape of the active site ;
5 (active site) no longer complementary (shape) to, substrate / starch ;
6 cannot form enzyme-substrate complexes ;
7 bile is released into the, small intestine / duodenum ;
8 bile is an alkaline mixture ;
9 neutralises the acidic mixture ;
10 idea of suitable pH for amylase to work in small intestine ;
MP1 A stomach contains gastric juice / HCl
All question bank results loaded