Chapter 4 - Enzymes

Question 1

Define activation energy.

Answer 1

The energy needed to start a chemical reaction.

Question 2

Why is there a need for enzymes to catalyst digestion reactions?

Answer 2

Nutrients like glucose are small and soluble; they can diffuse across the cell membrane easily. Nutrients like starch and large, complex molecules that cannot diffuse across the cell membrane. They have to be digested into smaller, simpler and soluble molecules in order to be absorbed by the cell.

Question 3

Where is amylase present and where and what does it digest?

Answer 3

Digest starch and present in mouth

Question 4

What does the maltose digest and where is it present?

Answer 4

Digest maltose to glucose and present in small intestines.

Question 5

What are anabolic reactions?

Answer 5

Build up complex substances

Question 6

What is a catabolic reaction?

Answer 6

Breaks down complex substances

Question 7

Name one example of an anabolic reaction.

Answer 7

Condensation of fatty acids and glycerol to synthesize fats.

Question 8

Name one example of an catabolic reaction.

Answer 8

Breaking down of glucose to release energy during cellular respiration

Question 9

Name 3 characteristics of enzymes.

Answer 9

1) speed up chemical reactions
2) required in minute amounts
3) highly specific in action

Question 10

Why is an enzyme highly specific in action?

Answer 10

An enzyme is specific due to its three-dimensional structure

Question 11

Explain the “lock-and-key” hypothesis.(7)

Answer 11

Enzyme is the lock and substrate is the jey. Substrate has a shape complementary to the active site of the enzyme. Enzyme and substrate bind to form enzyme-substrate complex; the enzyme remains chemically unchanged at the end of the reaction.

Question 12

Define denaturation.

Answer 12

The change in the 3 dimensional shape of an enzyme or protein is known as denaturation.

Question 13

What are the factors that cause denaturation?

Answer 13

1) Extreme high temperatures

2) Extreme pH

Question 14

What happens during denaturation?(7)

Answer 14

1) weak hydrogen bonds are broken.
2) enzymes lose the three dimensional structure.
3) they lose the active site.
4) they cannot bind with the substrate
5) no enzyme-substrate complex is formed.
6) no reaction
7) no products is formed

Question 15

How are enzymes affected by pH?

Answer 15

Different enzymes have different optimum pH, at which they are most active. Extreme changes in pH denatures the enzyme and causes it to lose its function.

Question 16

Describe and explain what happens to enzyme activity when temperature rises from very far below optimum temperature to very far above optimum temperature. (4)

Answer 16

1a) at low temperature, enzyme activity is slow.
1b) enzymes are inactive
2a) as the temperature rises, every 10C doubles the rate of reaction(only write if no graph)
2b) increases in kinetic energy, more collision, more enzyme-substrate complex formed
3a) at optimum temperature, enzyme activity is the highest
3b) enzymes most active
4a) beyond optimum temperature, enzyme activity decreases sharply.
4b) enzymes are denatured. Hydrogens bond break, they lose 3 dimensional shape and active site. Enzymes can no longer bind onto substrate and thus no enzyme-substrate complex is formed.

Question 17

Define enzymes.

Answer 17

Enzymes are biological catalysts made up of protein that has a specific 3 dimensional structure, which alters the rate of chemical reactions by lowering the activation energy needed for the reaction, speeding up rate of chemical reaction while remaining chemically unchanged at the end of the reaction.