Chapter 2: Enzymes

Question 1

Key Features of Enzymes

Answer 1

• Lowers the activation energy
• Increase the rate of rxn
• Does NOT alter the equilibrium constant (Keq)
• Are not changed or consumed in the rxn (will appear in both reactants or products)
• Are pH- and temperature-sensitive, with optimal activity at specific pH ranges and temperatures
• Do not effect the overall delta G, delta H, or delta S of the rxn
• Are specific for a particular rxn or class of rxns

Question 2

Types of Enzymes

Answer 2

1. Lyases
2. Isomerases
3. Ligases
4. Hydrolases
5. Oxidoreductases
6. Transferases

Question 3

Lyases

Answer 3

Splits molecule into 2 w/o H2O

OR

Synthesizes smaller molecules (i.e. synthases)

Question 4

Isomerases

Answer 4

Rearrangement of bonds within a molecule

Catalyzes rxns between stereoisomers and constitutional isomers

Question 5

Ligases

Answer 5

• Catalyzes the addition or synthesis rxns for larger molecules
• Often requires ATP

Question 6

Hydrolases

Answer 6

Breaking down compound into 2 molecules via H2O addition

i.e. phosphatase, peptidases, nucleases, lipases

Question 7

Oxidoreductases

Answer 7

• Catalyzes oxidation-reduction rxns
• Transfer of electrons between biological molecules

i.e. dehydrogenases (e- donor), reductases (e- donor), oxidases (e- acceptor)

Question 8

Reductant

Answer 8

Electron donor

Question 9

Oxidant

Answer 9

Electron acceptor

Question 10

Transferases

Answer 10

Catalyzes the movement of functional groups

i.e. aminotransferase, kinases

Question 11

Kinases

Answer 11

Catalyzes the transfer of a phosphate group, usually from ATP, to another molecule.

Question 12

Prosthetic groups

Answer 12

Tightly bound cofactors or coenzymes that are necessary for enzyme function

Question 13

Cofactors

Answer 13

• Inorganic molecules or metal ions

* Often ingested as dietary minerals

Question 14

Coenzymes

Answer 14

• Small organic groups
• Many are vitamins or derivatives of vitamins

i.e. NAD+ , FAD, and coenzyme A

Question 15

Which are the fat-soluble vitamins?

Answer 15

Vitamin A, D, E, K

Question 16

Which are the water soluble vitamins?

Answer 16

B complex Vitamins and Abscorbic Acid (Vitamin C)

Question 17

Vitamin B1

Answer 17

Thiamine

Question 18

Vitamin B2

Answer 18

Riboflavin

Question 19

Vitamin B3

Answer 19

Niacin

Question 20

Vitamin B5

Answer 20

Pantothenic Acid

Question 21

Vitamin B6

Answer 21

Pyridoxal Phosphate

Question 22

Vitamin B7

Answer 22

Biotin

Question 23

Vitamin B9

Answer 23

Folic Acid

Question 24

Vitamin B12

Answer 24

Cyanocobalamin

Question 25

Catalytic efficiency

Answer 25

kcat/Km Overall efficiency of enzyme, taking into consideration both how well the substrate binds AND how well the enzyme converts substrate to product.

Question 26

kcat

Answer 26

Turnover # Vmax/[E] How fast the enzyme can make products

Question 27

Km

Answer 27

* Binding efficiency * Higher the Km, lower the binding efficiency * [S] at Vmax/2

Question 28

How do enzymes affect rxn equilibrium?

Answer 28

It does NOT affect position or direction of equilibrium!!