Investigating how pH affects amylase activity:
Method
- Set up test tubes with different pH buffer solutions (pH 5, 6, 7, 8, 9)
- Add the same volume of starch solution to each tube
- Add the same volume of amylase enzyme to each tube
- Test samples every 30 seconds with iodine solution
- Record time taken for starch to completely disappear (iodine stays orange)
- Plot graph of pH vs time taken (or rate of reaction)
Expected Results
- pH 7: Fastest rate (optimal for amylase)
- pH 5-6 and pH 8-9: Slower rates
- Extreme pH: Very slow or no reaction (enzyme denatured)
Control Variables
- Temperature (use water bath)
- Enzyme concentration
- Substrate concentration
- Volume of solutions
- Time intervals for testing
This required practical covers Required Practical 5: Effect of pH on Enzyme Activity within Enzymes in Digestion for GCSE Biology. Enzyme structure and function, digestive enzymes, factors affecting enzyme activity, lock and key model, and practical investigations It is section 9 of 19 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
Practice questions for Enzymes in Digestion
What are enzymes?
Explain the effect of increasing temperature on enzyme activity.
Quick recall flashcards
What is an enzyme?
A biological catalyst that speeds up chemical reactions by lowering activation energy. Enzymes are proteins with specific 3D shapes.
What does lipase do?
Breaks down lipids (fats) into fatty acids and glycerol. Produced by pancreas, works in small intestine.