Enzymes

Question 1

Ribozymes?

Answer 1

• Catalytic RNA molecules

- No protein component

Question 2

Cofactor?

Answer 2

Non protein component required for activity

Question 3

Co enzyme?

Answer 3

Enzyme produced from a vitamin such as FAD or NAD

Question 4

Prosthethic group?

Answer 4

Covalently bound (or very closely associated) cofactor

Question 5

Apoenzyme?

Answer 5

Inactive enzyme that is activated when cofactor binds

Question 6

Holoenzyme?

Answer 6

The whole enzyme

Question 7

Why isn’t a spontaneous reaction instant?

Answer 7

Needs an activation energy

Question 8

What is the transition state?

Answer 8

• The instantaneous moment new chemical bonds are formed and old are broken
• From this point the reaction can go back to reactants or become products

Question 9

What type of bonds occur between substrate and enzyme

Answer 9

Non covalent

Question 10

What is the active site complementary to?

Answer 10

Transition state

Question 11

In what 3 ways do enzymes reduce activation energy?

Answer 11

• Reduce entropy
• Desolvation
• Induced fit

Question 12

How does reducing entropy reduce the activation energy?

Answer 12

Increases chance that substrates collide in the proper orientation

Question 13

How does desolvation lower activation energy?

Answer 13

H bonds with substrate/solution replaced by H bonds with substrate/enzyme

Question 14

What is the michaelis-menton equation?

Answer 14

E + S ES —-> P

Question 15

In the reversible step, which reaction is slower?

Answer 15

Reforming the products

Question 16

What is Km?

Answer 16

The substrate conc. when the reaction v is half the maximum

Question 17

What does Km measure?

Answer 17

The ratio of formation of ES from E + S, compared to the formation of E + S from ES

Question 18

What does Km show you?

Answer 18

The affinity of the enzyme for the substrate

Question 19

What does a large Km tell you?

Answer 19

• ES complex is unstable therefore

- More ES —-> E + S

Question 20

What does glucokinase catalyse?

Answer 20

Glucose + ATP to G-6-P

Question 21

What does an elevated level of creatine kinase allow you to diagnose?

Answer 21

• MI

- Infection

Question 22

What are the 2 reaction mechanisms that an enzyme catalysed reaction with 2 substrates can follow?

Answer 22

• Random w/ ternary complex
• Ordered w/ ternary complex
• No ternary complex

Question 23

What is random with a ternary?

Answer 23

• Either substrate can bind first

- Forms two products

Question 24

Ordered ternary reaction?

Answer 24

• One substrate attaches first, the other follows

- Forms one product

Question 25

What is the mechanism of reaction when no ternary complex forms?

Answer 25

• 2 reactions occurs
• 1st reaction with 1st substrate alters the enzyme and produces a product
• Altered enzyme can now bind to 2nd substrate and produces a second product

Question 26

What type of reactions have no ternary complex formation

Answer 26

Transamination

Question 27

How does pH alter enzyme function

Answer 27

pH will change the charge of amino acids in the sequence and can make the active set stop functioning

Question 28

Effect of a competitive inhibitor on Vmax and Km?

Answer 28

• Vmax same

- Km decreases

Question 29

Effect of a non competitive inhibitor on Vmax and Km

Answer 29

• Vmax decreases

- Km same