8_8_16 Enzymes

Question 1

how do they work

Answer 1

lock and key, but hand in glove is better because the glove (enzyme) changes shape to fit the hand (substrate)

Question 2

What do they do

Answer 2

stabilize the transition state (TS), reaction rate acceleration, done by expanding Boltzman distribution and lowering Ea of a reaction

Question 3

What confers catalytic activity

Answer 3

TS stabilization, proximity, covalent catalysis, acid/base catalysis, metal ion stabilization

Question 4

Example

Answer 4

Chymotrypsin, check out the lecture and your ye olde iPade

Question 5

What about unfavorable reactions

Answer 5

Couple to energetically favorable ones (like ATP hydrolysis), often at the same active site of an enzymatic reaction

Question 6

Enzyme Kinetics (Michaelis-Menten)

Answer 6

Km is dissociation constant of ES or ([E][S])/[ES]
Vmax=Kcat[E]
v=(Kcat[E][S])/(Km+[S]) = (Vmax[S])/(Km+[S])
get Kcat and Km by experimental measurement of rxn speed

Question 7

Lineweaver-Burke Plots

Answer 7

1/v = (Km/Vmax)(1/[S]) + 1/Vmax

Question 8

Allosteric enzymes

Answer 8

activators and inhibitors bind distally from the active site to increase/deacrease enzyme activity
Sigmoidal binding curve
2 kinds of activators/inhibitors: K type affects Km and V type affects Vmax
Think of the R and T states of Hemoglobin

Question 9

Competitive inhibition

Answer 9

Alters Vmax, binds to active site, usually mimics the substrate

Question 10

Noncompetitive inhibition

Answer 10

binds to a separate site and alters Km