People with lactose intolerance cannot digest lactose.
Lactose intolerance is due to a lack of the enzyme lactase.
(i) Which are the products of lactose digestion?
(1)
☐ A fructose and galactose
☐ B fructose and glucose
☐ C galactose and glucose
☐ D glucose and glucose
(ii) Explain how the three-dimensional structure of lactase affects the mechanism of action of this enzyme.
(3)
People with lactose intolerance can drink lactose-free milk.
Lactose-free milk is produced by treating milk with lactase.
There are two ways of removing lactose from milk:
Mixing a solution of lactase with the milk (free lactase)
Enclosing the lactase inside permeable beads and pouring the milk over them (immobilised lactase).
The diagrams show these two methods.
(i) Suggest one advantage of using immobilised lactase.
(1)
(ii) The table shows the effect of pH on the activity of free lactase and immobilised lactase.
pH | Activity of free lactase / a.u. | Activity of immobilised lactase / a.u. |
|---|---|---|
2 | 0 | 0 |
3 | 0 | 38 |
4 | 75 | 75 |
5 | 94 | 98 |
6 | 63 | 76 |
7 | 56 | 63 |
8 | 28 | 35 |
Explain the effects of pH on the activity of these two enzymes.
(4)
(iii) Suggest how the rate of activity of the lactase could be measured.
Include appropriate units in your answer.
(2)
Congenital lactose intolerance (CLI) is an extremely rare genetic disorder.
Most people with CLI are found in one country.
Suggest why most people with CLI are found in one country.
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