Enzymes

Question 1

oxidoreductases

Answer 1

catalyze redox reactions

Question 2

transferases

Answer 2

catalyze transfer of C, N, or P containing groups

Question 3

hydrolases

Answer 3

catalyze cleavage of bonds by addition of water

Question 4

lyases

Answer 4

catalyze cleavage of C-C, C-S, & certain C-N bonds

Question 5

Isomerases

Answer 5

catalyse racemization of optical or geometric isomers

change conformation

Question 6

ligases

Answer 6

catalyze formation of bonds b/w carbon and O,S,N coupled to hydrolysis of high energy phophates.

Question 7

kinases

Answer 7

dephosphorylation ATP & phosphorylates enzyme

Question 8

phophastases

Answer 8

dephosphorylation of enzyme

Question 9

Enzyme exists in inactive form (zymogen) that is activated by removal of a short peptide segment ( truncation)

Answer 9

Proteolytic cleavage to activate

Question 10

Covalent modification

Answer 10

to increase or decrease

activity, most common is phosphorylation

Question 11

Sequestration

Answer 11

enzyme forms inactive polymers

Question 12

(“other site”) regulation, both positive
   and negative ( homotropic, heterotropic)

Answer 12

Allosteric

Question 13

Induction

Answer 13

upregulation: increase gene expression, synthesis of more enzyme molecules

This is a slow process

Question 14

downregulation: decrease gene expression, decrease synthesis of enzyme molecules.

Answer 14

Repression

Question 15

What is the effect of an enzyme on a reaction?

Answer 15

The enzyme decreases the activation energy

Question 16

Define holoenzyme.

Answer 16

enzyme protein plus its cofactor

Question 17

An enzyme without its cofactor is called?

a) holoenzyme
b) prosthetic group
c) apoenzyme
d) E + S
e) zymogen

Answer 17

C) apoenzyme

Question 18

What is a zymogen?

Answer 18

inactive form of enzyme

Question 19

How is a zymogen activated?

Answer 19

by proteolitic cleavage of a short peptide segment

Question 20

phosphorylation is an examples of what kind of enzyme regulation?

Answer 20

covalent modification

Question 21

T/F. All the steps of the enzymatic reaction to produce a substrate is in equilibria

Answer 21

True.

Question 22

What step of enzymatic reaction occurs right before the product is produced?

Answer 22

transition state where complex is neither substrate or product.

Question 23

What are the components of the active site of an enzyme?

Answer 23

catalytic site and binding site

Question 24

Where on an enzyme does the reaction occur?

Answer 24

catalytic site

Question 25

Which is not an assumption of the Michaelis-Menten Kinetics?

a) ES complex is in equilibrium.
b) when enzyme is saturated all enzyme is in the form of ES complex
c) ES complex is in steady state
d) if all enzyme is ES then rate of product formation is maximal

Answer 25

a) ES complex is in steady state not equilibrium

Question 26

What kind of enzyme inhibition(s) cause(s) an increase in Km?

a) uncompetitive inhibitors
b) competitive inhibitors
c) non-competitive inhibitors
d) irreversible inhibitors
e) allosteric inhibitors

Answer 26

b) competitive inhibitors

Question 27

What kind of enzyme inhibition(s) cause(s) a decrease in Vmax?

a) uncompetitive inhibitors
b) competitive inhibitors
c) non-competitive inhibitors
d) irreversible inhibitors
e) allosteric inhibitors

Answer 27

C) non-competitive inhibitors
E) allosteric inhibitors

Allosteric inhibitors are non-competitive

Question 28

What kind of enzyme inhibition(s) cause(s) a decrease in Vmax and Km?

a) uncompetitive inhibitors
b) competitive inhibitors
c) non-competitive inhibitors
d) irreversible inhibitors
e) allosteric inhibitors

Answer 28

A) uncompetitive