Enzymes

Question 0

Define ‘Digestion’

Answer 0

Process by which complex, insoluble food substances are broken down into small, soluble substances.

Question 1

Why do food substances need to be converted into simpler substances?

Answer 1

1. Insoluble in water.

2. Too large to pass through pores in cell membrane.

Question 2

What is a catalyst?

Answer 2

Substance that can alter or speed up a chemical reaction, without itself being chemically changed at the end of the reaction.

Question 3

What are enzymes?

Answer 3

Substances that are protein in nature and can alter rate of chemical reactions without themselves being chemically changed at the end of reactions.

Question 4

What are the functions of enzymes?

Answer 4

Lowering the activation energy for a reaction.

Question 5

What are enzymes affected by?

Answer 5

1. Easily destroyed by heat, sensitive to pH and inactivated by poisons.
2. Shape of active site altered by heat, blocked by poison molecules.

Question 6

What is activation energy?

Answer 6

Energy needed to initiate chemical reactions. ‘Energy barrier’ that must be overcome before reaction can take place.

Question 7

What happens to the rate of reaction when amount of activation energy is greater?

Answer 7

Reaction rate will be slower.

Question 8

Which is the lock and which is the key?

Answer 8

1. Key is substrate.

2. Lock is active site of enzyme.

Question 9

Explain how a small quantity of an enzyme can bring about a large amount of chemical reactions.

Answer 9

1. Enzyme substrate complex formed long enough for reaction to be complete.
2. Same enzyme molecule can then catalyze reaction with another substrate molecule.
3. Presence of enzyme does not alter nature of end products of reaction.

Question 10

What are substrates?

Answer 10

Substances on which enzymes act on.

Question 11

What are products?

Answer 11

Substances which are made by enzymatic reaction.

Question 12

What is an active site?

Answer 12

Site with specific shape where substrate will bind onto enzyme.

Question 13

An enzyme is inactive at which temperatures?

Answer 13

Low temperatures.

Question 14

How does rising temperature increase enzyme reaction?

Answer 14

1. Rising temperature increases molecular motion.
2. Molecules move more quickly, frequency of collision between substrate and enzyme molecules increases.
3. Greater probability of reaction taking place.

Question 15

What happens to the reaction rate of enzymes for every 10 degrees rise in temperature?

Answer 15

Rate of reaction doubles.

Question 16

Define ‘optimum temperature’.

Answer 16

Temperature at which maximum reaction occurs.