Enzymes

Question 1

What is a catalyst?

Answer 1

• Reduces activation energy of a reaction

- Has no effect on the overall free energy change of the reaction

Question 2

What are enzymes?

Answer 2

• Bio-catalysts
• Able to lower activation energy
• Speed up biochemical reactions
• Can be reused

Question 3

What are the 6 groups that enzymes can be classified into?

Answer 3

1. Oxidase/Reductase - catalyze oxidation-reduction reactions
2. Transferase - Catalyze the transfer of functional groups
3. Hydrolase - Catalyze hydrolysis reactions
4. Lyase - Catalyze the addition of double bonds/its reverse
5. Isomerase - Catalyze isomerization reactions
6. Ligase - Catalyze the formation of bonds with ATP cleavage

Question 4

What are the 2 hypotheses of enzyme-substrate binding?

Answer 4

Lock & Key hypothesis:
Substrate fits precisely into the active site of the enzyme

Induced fit hypothesis:
Substrate and active site change shape slightly during binding

Question 5

How do enzymes increase the rate of biochemical reactions?

Answer 5

Active site of the enzyme:

1. Forms transient bonds with the substrate
2. Bring multiple substrates close together to allow reaction to take place
3. Stabilizes high energy transition states
4. Reducing activation energy

Question 6

What are the factors affecting enzyme activity?

Answer 6

Each enzyme works best at a certain pH and temperature
- Enzyme activity decreases when pH/temperature is below/above optimum temperature/pH
OR
- Non-covalent forces break, protein/enzyme shape is lost

Question 7

What is the x-axis and y-axis of a progress curve?

Answer 7

X-axis: time

Y-axis: amount of product formed

Question 8

What is the x-axis and y-axis of a Michaelis-Menten curve?

Answer 8

X-axis: substrate concentration

Y-axis: rate of reaction

Question 9

What does the term Vmax and Km define?

Answer 9

Vmax: maximum velocity of a reaction
Km: reflects on the affinity of attraction between enzyme and substrate