Chapter 8: Enzymes

Question 1

Competitive Inhibition

Answer 1

Binds to the active site

K_m increases

V_max unchanged

Question 2

Answer 2

Competitive inhibition

K_m increases

V_max unchanged

Question 3

Answer 3

Competitive inhibition

K_m increases

V_max unchanged

Question 4

Uncompetitive inhibition

Answer 4

Binds ONLY to the enzyme-substrate complex

K_m decreases

V_max decreases

Question 5

Answer 5

Uncompetitive OR noncompetitive inhibition

Uncompetitive

• K_m decreases
• V_max decreases

Noncompetitive

• K_m unchanged
• V_max decreases

Question 6

Answer 6

Uncompetitive

K_m decreases

V_max decreases

Question 7

Noncompetitive inhibition

Answer 7

Binds to the enzyme-substrate complex OR the free enzyme

K_m unchanged

V_max decreases

Question 8

Answer 8

Noncompetitive inhibition

K_m unchanged

V_max decreases

Question 9

Group specific inhibitors

Answer 9

Irreversible inhibitor that covalently modifies one specific amino acid residue

Binds to specific side chains of amino acids

Question 10

Affinity label inhibitors

Answer 10

Irreversible inhibitor that resemble the structure of the substrate molecules

Occupies the active site but does NOT undergo enzymatic modification

Question 11

Suicide inhibitors

Answer 11

Irreversible inhibitor that mimics natural substrate to target normal catalytic mechanism

Binds like any regular substrate to the active site but DOES undergo enzymatic modification

Inactivation comes from the intermediate that’s formed in the middle of the process

Question 12

Enzyme features

Answer 12

Enzymes DO:

• Lower activation energy
• Increase rate of reaction

Enymes DON’T:

• Alter equilibrium constant
• Affect overall ΔG of reaction

Question 13

Enzyme classes

Answer 13

Under the Enzyme Commission (EC), enzymes are divided into six major classes based on general function:

Over The HILL

Oxidoreductases
Transferases
Hydrolases
Isomerases
Lysases
Ligases

Question 14

Oxidoreductase

Answer 14

Catalyze the transfer of electrons from one molecule (the oxidant, hydrogen donor, or electron donor) to another molecule (the reductant, hydrogen acceptor, or electron acceptor)

E.g.:

• Dehydrogenases
• Oxidases

Question 15

Transferase

Answer 15

Catalyze the transfer of specific functional groups (methyl or glycosyl group) from one molecule to another

E.g.:

• Transaminases
• Kinases

Question 16

Hydrolase

Answer 16

Use water to break a chemical bond

Typically results in dividing a larger molecule into smaller molecules

E.g.:

• Digestive enzymes

Question 17

Isomerase

Answer 17

Facilitate intramolecular rearrangements in which bonds are broken and formed

Question 18

Lyase

Answer 18

Catalyzes the breaking of chemical bonds by means other than hydrolysis and oxidation

Can also perform elimination reactions that form double or triple bonds

Question 19

Ligase

Answer 19

Catalyze the joining of two molecules by forming a new chemical bond

Question 20

Apoenzyme

Answer 20

An enzyme that is lacking its cofactor

Question 21

Haloenzyme

Answer 21

An enzyme that has its corresponding cofactor