Enzyme kinetics and inhibition

Question 1

what is enzyme kinetics used for?

Answer 1

to determine quantitative relationships

Question 2

what is a progress curve used for?

Answer 2

to measure product formation as a function of time

Question 3

why does the slope of a progress curve begin by being linear and the gradually decrease?

Answer 3

because of product inhibition or enzyme inactivation

Question 4

what do rate equations do?

Answer 4

describe chemical processes

Question 5

what is the rate equation for a unimolecular reaction? bimolecular?

Answer 5

v=K[A]

v=K[A][B]

Question 6

what with the rate of product formation generally increase with?

Answer 6

the amount of enzyme present

Question 7

what is the michaelis-menten equation?

Answer 7

v=vmax[S]/Km+[S]

Question 8

what is vmax?

Answer 8

where the reaction velocity reaches its plateau

Question 9

what does reaction rate depend on?

Answer 9

[ES]

Question 10

what does Km =?

Answer 10

K-1 + K2/K1

Question 11

what indicates catalytic efficiency?

Answer 11

Kcat/Km

Question 12

what does Kcat indicate?

Answer 12

how fast an enzyme can act, the number of catalytic cycles that each active site undergoes per time

Question 13

what does Kcat=?

Answer 13

vmax/[E]total

Question 14

for the simplest enzyme pathway what does Kcat =?

Answer 14

K2

Question 15

what does a high affinity for substrate do to the progress curve?

Answer 15

pushes it left

Question 16

on a progress curve at Vmax/2 what is Km?

Answer 16

Km = [S]

Question 17

what is Km?

Answer 17

substrate affinity

Question 18

what is catalytic perfection?

Answer 18

when the enzymes rate is completely controlled by diffusion
Kcat/Km = 10^8-10^9

Question 19

what does a lineweaver-burk plot accomplish?

Answer 19

it linearizes michaelis-menten data

plots 1/V vs 1/[S]

Question 20

what does a lineweaver-burk plot give?

Answer 20

a negative slope, yintercept = 1/vmax, xintercept=-1/Km

Question 21

what two types of enzyme inhibition are there?

Answer 21

reversible or irreversible

Question 22

what is irreversible enzyme inhibition?

Answer 22

molecules that covalently modify the active site

Question 23

what is a transition state analog?

Answer 23

something that is often a better inhibitor than substrate analogs because they lower the ∆G

Question 24

what are reversible inhibitors?

Answer 24

normally bind to enzymes non-covalently and can be classified by where the bind and what reaction steps they block; these are kinetically distinguishable

Question 25

what are some different types of reversible inhibitors? (4)

Answer 25

competitive, non-competitive, uncompetitive, mixed

Question 26

what is a competitive inhibitor?

Answer 26

it binds at the active site so it competes with the substrate, depends on the [S] vs [I], mutually exclusive with the substrate

Question 27

what does a competitive inhibitor appear to increase? Vmax?

Answer 27

Km

no change

Question 28

what way does a competitive inhibitor push the M-M plot?

Answer 28

right, makes the L-B plots slope steeper

Question 29

what is a noncompetitive inhibitor?

Answer 29

substrate and the inhibitor are not mutually exclusive bust the ESI complex is less active than the ES complex
there are separate binding sites on the enzyme

Question 30

non-competitive inhibitors effect on Km and Vmax? M-M plot?

Answer 30

decreases Vmax, no change to Km

M-M plot pushed down

Question 31

whats an allosteric enzyme?

Answer 31

often have multiple subunits and show cooperativity: the subunits interact to give a sigmoidal curve instead of a hyperbolic one (M-M plot), thus they do not easily fit the M-M model.

Question 32

how do allosteric effectors inhibit or activate?

Answer 32

inhibit using a pathway end product activate by a co-substrate, often involves an early or/and a committed step in a metabolic pathway