5-2: Enzymes

Question 1

Enzymes act as…

Answer 1

catalysts

Question 2

RNA enzymes are called…

Answer 2

Ribozymes

Question 3

Enzymes participate in the reaction (T/F)

Answer 3

False

Question 4

Why won’t an exergonic reaction occur at an appreciable rate without an enzyme

Answer 4

Activation energy: bonds need to be broken to initiate reaction, which takes a fair amount of energy without a catalyst

Question 5

How do enzymes work

Answer 5

Lower activation energy of reaction = increased rate of reaction
DO NOT change the energetics (deltaG) of the reaction

Question 6

Four ways enzymes increase reaction rates and lower activation energies

Answer 6

1. increase local concentrations of substrates at the active site of the enzyme
2. orient molecules at the active site
3. alter electronic distribution and conformation structure of the substrates = increased reactivity
4. stabilize the transition states of the reaction

Question 7

What are coenzymes or prosthetic groups

Answer 7

Coenzyme = molecule that binds active site of enzyme to assist in catalysis. loosely bound

Prosthetic group = bound to enzyme, change from one form to another and back in catalytic cycle

Question 8

How do enzymes influence cell metabolism

Answer 8

Catalyze reactions, allowing for accumulation of specific products
Products are then used as reactants in others

Question 9

How are enzyme activities controlled

Answer 9

Regulating the amounts of the enzymes or controlling their activity

Question 10

What are competitive inhibitors

Answer 10

Fit in the same active site as the substrate and inhibit substrate binding, control enzyme activity

Question 11

How do allosteric inhibitors/activators work

Answer 11

Conformationally modify the catalytic site of an enzyme by binding the allosteric site

Question 12

What are allosteric activators

Answer 12

Positive effects: promote binding of substrate and catalysis
Conformation change of active site to fit substrate, which is converted to product

Question 13

What are allosteric inhibitors

Answer 13

Negative effectors: prevent substrate from binding
Binds regulatory site, conformation change in active site, substrate can not fit/bind, reaction inhibited

Question 14

What is feedback inhibition

Answer 14

End product of pathway binds to first enzyme in pathway and inhibits its activity
Shuts down its own production when in excess
Once used up, pathway resumes