Summative Practice Chapter 5 – Question 1 – 4 (Form 4 Biology Textbook Exercise and Answer)

Question 1:
Some chefs sometimes wrap meat in papaya leaves and the meat is marinated for 5 hours before it is cooked. What is the purpose of wrapping with papaya leaves?

To tenderise meat.

Question 2:
Why are apples that have been boiled after they are peeled, do not change colour to brown?

Apples contain a type of enzyme that transforms the colour of apple tissue to brown after it is peeled and left for a while. If the apple is boiled, the enzyme becomes denatured causing the apple to not turn brown.

Question 3:
(a) Enzymes are used in industries and everyday life. Explain the use of enzymes to extract agar-agar from seaweed.
(b) State one function of lipase in the food industry.

(a) Cellulase breaks down the cell wall of seaweed and separates the agar-agar from it.

(b) Lipase is used in the production of cheese.

Question 4:
(a) State two characteristics of enzymes.

(b) Explain why only certain substrate can combine with enzymes.

(c) (i) What is the hypothesis that is used to explain the mechanism of enzyme action? In this hypothesis, what represents the structure of enzymes and the structure of the substrate?
(ii) Which characteristics of enzymes can explain this hypothesis?

Enzyme reactions are specific. The enzyme’s active site does not change shape once the reaction is completed.

The structure of the substrate molecule matches the structure of the enzyme molecule which allows them to bind together.
Other substrate molecules that do not have the structure that matches the enzyme molecule will not be able to bind to it.

Lock and key hypothesis. Enzyme is represented by the lock while substrate is represented by the key.

The enzyme reaction is specific, where only one type of enzyme can react with a certain type of substrate.

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