L1 Enzymes

Question 1

Lyases is a type of enzyme that catalyze which type of reaction?

Answer 1

Group elimination to form double bonds

Question 2

Ligases is a type of enzyme that catalyze which type of reaction?

Answer 2

Bond formation coupled with ATP hydrolysis

Question 3

Lactate dehydrogenase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 3

Oxidoreductases

Question 4

Alanine transaminase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 4

Transferases

Question 5

Pyrophosphatase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 5

Hydrolases

Question 6

Pyruvate decarboxylase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 6

Lyases

Question 7

Alanine racemase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 7

Isomerases

Question 8

Glutamine synthetase is an example of which type of enzyme?

A. Oxidoreductases
B. Transferases
C. Hydrolases
D. Lyases
E. Isomerases
F. Ligases

Answer 8

Ligases

Question 9

Competitive inhibition can be overcome by what?

Answer 9

(1) Increasing substrate concentration
(2) Increasing reaction time
* Could not be overcame by increasing reaction temperature

Question 10

What are the three essential assumptions for driving the M-M equation?

Answer 10

(1) Early in the reaction (close to time zero), there is no ES formation from E + P because [P] is negligible, hence k-2 can be ignored
(2) Steady state assumption for enzyme-substrate complex concentration [ES]
(3) Maximum reaction velocity (Vmax) occurs when enzyme is saturated with substrate

Question 11

Among Km, Vmax and Kcat, which can be determined experimentally and how?

Answer 11

Km and Vmax, by measuring of initial velocities at a series of substrate concentrations and a fixed enzyme concentration

Question 12

How to calculate Kcat?

Answer 12

kcat = Vmax /[E]total

Question 13

Irreversible inhibitor binds to the enzyme through covalent bonds or non-covalent bond?

Answer 13

Covalent bonds

Question 14

A type of inhibitor raises Km without effecting Vmax, what type of inhibitor is it?

Answer 14

Competitive inhibitor

Question 15

What does the competitive inhibitor bind to?

Answer 15

Free enzyme

Question 16

What does the uncompetitive inhibitor bind to?

Answer 16

ES complex

Question 17

A type of inhibitor lowers both Km and Vmax, what type of inhibitor is it?

Answer 17

Uncompetitive inhibitor

Question 18

Does the uncompetitive inhibitor raise the enzyme affinity or lower it? Why?

Answer 18

Raise it.
As it binds to the ES complex, the amount of ES complex is reduced. As a result, formation of ES from E + S will be enhanced. This means binding of S to E is enhanced, therefore Km is lowered, and the enzyme affinity is raised.

Question 19

What does the noncompetitive inhibitor bind to?

Answer 19

E or ES complex

Question 20

A type of inhibitor lowers Vmax, but Km remains the same, what type of inhibitor is it?

Answer 20

Non-competitive inhibitor

Question 21

Is the regulation by covalent modification usually reversible or irreversible?

Answer 21

Reversible

Question 21

What are the two common regulation ways of enzyme activity?

Answer 21

Allosteric regulation and covalent modification

Question 22

Which one is faster, allosteric regulation or covalent modification?

Answer 22

allosteric regulation

Question 23

Why phosphorating has an impact on enzyme structure?

Answer 23

Because phosphates are bulky negatively charged groups which affect enzyme conformation