Module 3

Question 1

What are the 6 classes of enzymes?

Answer 1

Oxido-reductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase

Question 2

Class of enzymes capable of catalyzing the reaction of joining two large molecules

Answer 2

Ligase

Question 3

Class of enzymes which catalyze the cleavage of covalent bond using water

Answer 3

Hydrolase

Question 4

Class of enzymes which mediate transfer of electrons from one molecule to another.

Answer 4

Oxido-reductase

Question 5

Class of enzymes that catalyzes the formation of double bonds by removal of groups or addition of groups to double bonds

Answer 5

Lyase

Question 6

Class of enzymes which catalyze intramolecular rearrangements

Answer 6

Isomerase

Question 7

Class of enzymes responsible for catalyzing redox reactions.

Answer 7

Oxido-reductase

Question 8

Class of enzymes which catalyze the transfer of a group of atom from a donor substrate to an accepting compound.

Answer 8

Transferase

Question 9

Enzymes that catalyze the joining of specified molecules or groups

Answer 9

Lyase

Question 10

Characteristic of enzyme reactions which became the basis for the “lock and key” model.

Answer 10

Geometric Complementarity

Question 11

Happens when amino acid residues
that form the binding site are
arranged to specifically attract the
substrate

Answer 11

Electronic Complementarity

Question 12

There are four digits in the Enzyme Code Notation. Name what each digits stand for.

Answer 12

1st - class name
2nd - subclass
3rd - accepting functional group
4th - accepting molecule

Question 13

First digit of Enzyme Code Notation of the enzyme DNA polymerase

Answer 13

2

Question 14

First digit of Enzyme Code Notation of the enzyme carbonic anhydrase

Answer 14

4

Question 15

First digit of Enzyme Code Notation and full name of the enzyme TPP

Answer 15

5. (Triose phosphate isomerase)

Question 16

First digit of Enzyme Code Notation of the enzyme pyruvate carboxylase

Answer 16

6

Question 17

First digit of Enzyme Code Notation of the enzyme pyruvate dehydrogenase

Answer 17

1

Question 18

First digit of Enzyme Code Notation of the enzyme acetylcholinesterase

Answer 18

3

Question 19

T or F: Coenzymes may be an organic or organometallic molecule

Answer 19

True

Question 20

T or F: Pure metal ions are not considered coenzymes

Answer 20

True

Question 21

T or F: Pure metal ions cannot be cofactors

Answer 21

False

Question 22

This compound is an obligatory oxidizing agent in the alcohol dehydrogenase reaction.

Answer 22

NAD+

Question 23

True or False:
I. Both enzymes and coenzymes are chemically changed by the reaction.
II Both enzymes and coenzymes are not chemically changed by the reaction.
III. Coenzymes are chemically changed by the reaction.

Answer 23

I. F
II. F
III. T

Question 24

Coenzymes are __________ in order to complete the catalytic cycle.

Answer 24

Regenerated/returned to its original state

Question 25

It is the enzymatically inactive protein resulting from the removal of a cofactor

Answer 25

Apoenzyme

Question 26

It is a catalytically active enzyme-cofactor

Answer 26

Holoenzyme

Question 27

What are the two factors influencing the activity of enzymes?

Answer 27

Temperature and pH

Question 28

The rate decline begins in the temperature range of ____________.

Answer 28

50 °C to 60 °C

Question 29

The optimal pH for most enzymes.

Answer 29

6 - 8

Question 30

T or F: The free energy of catalyzed reaction is higher than uncatalyzed reaction.

Answer 30

False. There is no difference.

Question 31

T or F: A catalyzed reaction has lower activation energy than an uncatalyzed reaction does.

Answer 31

True.

Question 32

T or F: Catalysts changed the equilibrium of the reactants and products, favoring the formation of products.

Answer 32

False.

Question 33

Catalysts usually act by forming a ___________________ with the reactant, thus stabilizing the __________________.

Answer 33

transient complex; transition state

Question 34

This describes the region of the enzyme in which the substrate binds.

Answer 34

Active site

Question 35

Characteristic of the active site wherein it only accept ONLY ONE type of molecule.

Answer 35

Absolute Specificity

Question 36

T or F: Active sites with absolute specificity will never discriminate between the enantiomers of a compound

Answer 36

False.
Note: Enantiomers -> Levorotatory or Dextrorotatory

Question 37

T or F: The active site is the largest part of the enzyme.

Answer 37

False. It is relatively small.

Question 38

What are the three models of the substrate-enzyme binding?

Answer 38

• Lock and Key Model
• Induced Fit Model
• Transition State Model

Question 39

This model assumes that an active site is flexible and undergoes conformational change until the substrate is completely bound.

Answer 39

Induced Fit Model

Question 40

The active site is able to accept only a specific type of substrate

Answer 40

Lock and Key Model

Question 41

Active site and the binding portion of the substrate are not exactly complementary

Answer 41

Induced Fit Model

Question 42

T or F: In the Induced Fit Model, after the products move away from the enzyme, the enzyme will retain its shape.

Answer 42

False. It returns to its initial shape.

Question 43

Five main types of catalytic mechanisms.

Answer 43

1. Acid-base catalysis
2. Covalent catalysis
3. Metal ion catalysis
4. Proximity and orientation effects
5. Preferential binding of the transition state complex

Question 44

This catalysis requires a nucleophile to form transient covalent bonds between enzyme and substrate, lowering the activation energy.

Answer 44

Covalent catalysis

Question 45

This type of catalysis makes the activation energy higher than uncatalyzed reaction.

Answer 45

No answer. All catalysts lower the activation energy.