4.2 Factors affecting enzyme activity

Question 1

What 2 things must happen for an enzyme to catalyse a reaction?

Answer 1

1. Come into contact with substrate

2. Enzyme must be complementary to substrate

Question 2

What happens when the the temperature of a reaction environment increases?

Answer 2

Kinetic energy of particles increases

Particles move faster and collide more frequently

Question 3

What is the effect of increasing temperature in an enzyme-controlled reaction?

Answer 3

More frequent successful collisions between substrate and enzyme - this increases rate of reaction

Question 4

1. Define the temperature coefficient of a reaction

2. Refer to how this affects an enzyme-controlled reaction

Answer 4

1. A measure of how much the rate of reaction increases with a 10°C increase in temperature
2. Usually taken as two, meaning the rate of reaction doubles with a 10°C temperature increase

Question 5

What type of molecule are enzymes?

Answer 5

Proteins

Question 6

What happens to proteins (enzymes) at high temperatures?

Answer 6

1. Bonds holding the protein (enzyme) vibrate more
2. As temperature increases, vibration increases until the bonds break
3. Breaking of bonds changes the tertiary structure of the protein (enzyme)
4. Enzyme changes shape - it has denatured

Question 7

How does denaturing affect an enzyme’s active site?

Answer 7

Enzyme’s active site changes shape and is no longer complementary to the substrate

Question 8

How does denaturing of an enzyme affect the substrate?

Answer 8

Substrate can no longer fit into the active site and enzyme will stop functioning as a catalyst

Question 9

Define what ‘optimum temperature’ means

Answer 9

Temperature at which the enzyme has the highest rate of activity

Question 10

What is the optimum temperature for enzymes inside of the homo sapiens of class mammalia and order primates body?

Answer 10

40°C

Question 11

What is the optimum temperature of enzymes in thermophilic bacteria (in hot springs)?

Answer 11

70°C

Question 12

What is the optimum temperature of enzymes in psychrophilic organisms (in cold regions e.g. the poles)?

Answer 12

> 5°C

Question 13

What happens to the rate of reaction after an enzyme denatures?

Answer 13

Rate of reaction rapidly decreases

Question 14

Define what temperature coefficient (Q10) is.

Answer 14

Measure of how much rate of reaction increases with a 10°C increase

Question 15

What does a ‘change in pH’ refer to?

Answer 15

H ion conc. - low pH = more H ions, high pH = less H ions

Question 16

What does ‘optimum pH’ refer to?

Answer 16

Active site will only be the right shape at a specific H ion concentration

Question 17

What is renaturation?

Answer 17

pH changes from optimum = enzyme’s active site changes shape.
pH returns to optimum = enzyme returns to its normal shape and can catalyse again

Question 18

Can an enzyme be denatured by the incorrect pH? Explain why.

Answer 18

Yes - when pH change is significant, the enzyme’s change in shape is irreversible, so the enzyme is denatured

Question 19

What does an increased concentration of substrates lead to?

Answer 19

Higher collision with active sites of enzymes, so increased formation of enzyme-substrate complexes.
Rate of reaction increases.

Question 20

What effect does the increase in enzyme concentration have?

Answer 20

More active sites in a particular area so enzyme-substrate complexes are formed at a faster rate

Question 21

What is the Vmax?

Answer 21

The point to which the rate of reaction can increase

Question 22

In relation to active sites and substrates, what happens once the Vmax is reached?

Answer 22

All available active sites are occupied by substrates, so no more enzyme-substrate complexes can form until products are released from active sites