Lesson 8 - enzymes and pH

Question 1

What does pH measure, and what do lower and higher pH values mean?

Answer 1

pH measures how acidic or alkaline a solution is:

Lower pH (1–6): Acidic
pH 7: Neutral
Higher pH (8–14): Alkaline

Question 2

How does pH affect enzyme activity?

Answer 2

Each enzyme works best at its optimum pH. If the pH is too high or too low, the enzyme’s active site can change shape, and the enzyme becomes less effective or denatured.

Question 3

What is the optimum pH for enzymes in the stomach?

Answer 3

The optimum pH for enzymes in the stomach is around pH 2, because it is an acidic environment.

Question 4

What is the optimum pH for enzymes in the small intestine, such as amylase and lipase?

Answer 4

The optimum pH for enzymes like amylase and lipase in the small intestine is slightly alkaline, around pH 7–8.

Question 5

How does bile help enzymes in the small intestine?

Answer 5

Bile neutralises the acidic food coming from the stomach, creating an alkaline environment for enzymes in the small intestine to work effectively.

Question 6

How can you identify the optimum pH of an enzyme on a graph?

Answer 6

The optimum pH is the highest point of the curve on a graph of enzyme activity versus pH. This is where the enzyme works fastest.

Question 7

What happens to enzymes when the pH is too far from their optimum?

Answer 7

Enzymes become denatured when the pH is too far from their optimum. The active site changes shape, so the substrate can no longer bind.

Question 8

Why is pH important for enzyme activity in digestion?

Answer 8

Different enzymes work in different parts of the digestive system, which have different pH levels. For example:

Stomach (acidic): works best at low pH.
Small intestine (alkaline): Amylase and lipase work best at higher pH.