Enzymes - Practise Questions

Question 1

Amylase is an enzyme that breaks down
starch. Explain how amylase breaks down
starch. Answer in terms of the ‘lock and key
theory’. (3)

Answer 1

● Starch / substrate binds to active site (of enzyme)
● Shape of active site and substrate are complementary
● A chemical reaction occurs to produce smaller
molecules OR bonds between the (starch) molecules are
broken to produce smaller molecules

Question 2

A person has a tumour blocking the tube
leading from the gall bladder to the small
intestine. Explain why this person would
have difficulty digesting fat. (4)

Answer 2

● No / less bile reaches the small intestine
● So less / no emulsification of fat
● So smaller surface area for lipase to break down fat
● pH of small intestine not neutralised
● So lipase is not at its optimum pH to break down fat

Question 3

One symptom of pancreatic cancer is
weight loss. Explain how pancreatic cancer
may cause a person to lose weight. Do not
refer to hormones in your answer. (4)

Answer 3

● Reduced / no enzyme production from pancreas
● Food is not broken down / digested fully
● Eg. less glucose absorbed
● So less glucose available for respiration so more fat used
up in metabolism / respiration
● Eg. fewer fatty acids absorbed
● So fewer fatty acids available so less fat is stored