monsachharide

Question 1

Cow’s milk contains the sugar lactose. Many cats are unable to digest cow’s milk because they are lactose intolerant.

Cow’s milk can be made suitable for these cats by treating it with the enzyme lactase to hydrolyse lactose. This makes the cow’s milk lactose-free. Beads are coated with lactase and placed in a tube, as shown in the diagram below. Cow’s milk flows over the beads and the lactose is hydrolysed.

(a) Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow’s milk.

Suggest three reasons why it is more efficient to attach lactase to the beads.

Answer 1

Lactase / beads) can be reused / not washed away;

1. Accept lactase / beads not wasted
2. Less lactase used is insufficient
3. No need to remove from milk;
4. Accept lactase not present in milk.
5. Allows continuous process;
6. The enzyme is more stable;
7. Avoid end-product inhibition.

Question 2

In humans, the enzyme maltase breaks down maltose to glucose.
This takes place at normal body temperature.

Explain why maltase:

• only breaks down maltose
• allows this reaction to take place at normal body temperature.

Answer 2

Tertiary structure / 3D shape of enzyme (means);

Accept references to active site

2. Active site complementary to maltose / substrate / maltose fits into active site / active site and substrate fit like a lock and key;

Idea of shapes fitting together

3. Description of induced fit;
4. Enzyme is a catalyst / lowers activation energy / energy required for reaction;

Accept “provides alternative pathway for the reaction at a lower energy level”

5. By forming enzyme-substrate complex;