Enzymes I BI25M7-2015_

Question 1

What is the term for the active site complementary to the transition state?

Answer 1

CATALYSIS

Question 2

What is the class number and name for enzymes that transfer electrons?

Answer 2

1 - Oxidoreductases

Question 3

What type of reaction do Transferases catalyze?

Answer 3

Group transfers

Question 4

What is the function of Hydrolases?

Answer 4

Hydrolysis (transfer chemical groups to water)

Question 5

What do Lyases do?

Answer 5

Form, or add groups to double bonds

Question 6

What is the role of Isomerases?

Answer 6

Transfer groups within molecules (form isomers)

Question 7

What type of bonds do Ligases form?

Answer 7

C-C, C-S, C-O and C-N bonds (coupled to ATP cleavage)

Question 8

What suffix do nearly all enzymes end with?

Answer 8

-ase

Question 9

What does the term ‘Apoenzyme’ refer to?

Answer 9

The protein component of an enzyme that contains a cofactor

Question 10

Define ‘Holoenzyme’.

Answer 10

Whole enzyme – the apoenzyme plus the cofactor(s)

Question 11

What is the substrate in enzyme reactions?

Answer 11

Molecule acted on by the enzyme

Question 12

What is the active site of an enzyme?

Answer 12

Part of the enzyme in which the substrate binds and is acted upon

Question 13

What is a Prosthetic group?

Answer 13

Cofactor covalently bound to the enzyme or very tightly associated with the enzyme

Question 14

What is a Coenzyme?

Answer 14

Complex organic molecule, usually produced from a vitamin

Question 15

What vitamin is FAD a derivative of?

Answer 15

Riboflavin

Question 16

What vitamin is NAD+ derived from?

Answer 16

Niacin

Question 17

What is the role of Coenzyme A?

Answer 17

Derived from Pantothenate

Question 18

Define ‘Cofactor’.

Answer 18

Non-protein component needed for activity

Question 19

What ions can act as cofactors for enzymes?

Answer 19

• Fe2+ or Fe3+
• K+
• Mg2+

Question 20

What is an enzyme?

Answer 20

Globular protein that acts as a biological catalyst

Question 21

How do enzymes differ from chemical catalysts?

Answer 21

Catalyses very high reaction rates and shows great reaction specificity

Question 22

What conditions do enzymes work in?

Answer 22

Mild temperature/pH conditions

Question 23

True or False: Enzymes can move reaction equilibria.

Answer 23

False

Question 24

What do enzymes do?

Answer 24

• Increase rates of spontaneous reactions
• Lower the activation energy of biochemical reactions
• Accelerate movement towards reaction equilibrium

Question 25

What is Gibbs Free-Energy (G)?

Answer 25

Useful energy generated from cellular reactions

Question 26

What must be true for spontaneous reactions in terms of ΔG?

Answer 26

Must have a –ve ΔG value

Question 27

What is the energy barrier in a reaction?

Answer 27

Energy required to position chemical groups correctly, bond rearrangements, etc.

Question 28

What does the transition state represent?

Answer 28

The moment that chemical bonds are formed and broken

Question 29

What is initial velocity (V0) in enzyme kinetics?

Answer 29

The rate of reaction at the start, assuming initial substrate concentration does not change

Question 30

What happens to the reaction rate as substrate concentration increases?

Answer 30

Higher initial rate of reaction

Question 31

What is Vmax?

Answer 31

Maximum reaction velocity when all enzyme active sites are saturated with substrate

Question 32

How do enzymes reduce activation energy?

Answer 32

* Entropy reduction * Desolvation * Induced fit

Question 33

What does the term 'binding energy' refer to?

Answer 33

Non-covalent bonds formed between enzymes and substrate molecules