Enxyme Kinetics I

Question 1

no matter how many substrate, is there a limit to Product

Answer 1

yes, there is

Question 2

as [S] rises, what happens to Vo

Answer 2

Vo rises too but only at initial point

Question 3

what is the reaction order for E+S»> ES

Answer 3

zero-order when [S]&raquo_space; [E]

Question 4

which is the rate limiting step between ES»>E+P and E + S&raquo_space;>ES

Answer 4

ES»>E+P (k2)

Question 5

Is V0 directly proportional to [S] always true

Answer 5

no, the enzyme differs

Question 6

What is the theoretical speed limit at which an enzyme will not work any faster because it has reached it speed limit

Answer 6

Vmax

Question 7

As [S] increases, Vo approaches Vmax true/false

Answer 7

true

Question 8

As [S] increases, what happens to [ES]

Answer 8

it increases too

Question 9

when does [ES] stop increasing

Answer 9

when [ES] =[E]T because [E]T=[ES] + [E]

Question 10

Km is the

Answer 10

Michaelis constant

Question 11

Km is related to

Answer 11

measure of the affinity of the enzyme for the substrate units in terms of concentration

Question 12

Km is the combination of which constants

Answer 12

k2+k1/k1

Question 13

Km is a measure of

Answer 13

ES binding or affinity

Question 14

Small Km means

Answer 14

tight binding

Question 15

large Km means

Answer 15

weak binding

Question 16

Describe low [S] and high [S]

Answer 16

at low [S[, 1/2 Vmax =Km
at high [S] Vo= Vmax[S] /Km and Vo=Vmax

Question 17

this is the # molecule of substrate converted to product by 1 enzyme molecule in 1 second (units of s-1)

Answer 17

Kcat

Question 18

What is the rate-limiting step at saturation

Answer 18

Kcat

Question 19

What tells you how good an enzyme is when they are working on 2 different substrates

Answer 19

specificity constant Vo= Kcat[E]T[S]/[S] + Km

Question 20

what is Vo when [s] &laquo_space;Km

Answer 20

Vo=Kcat [E]T[S]/Km

Question 21

Kcat/Km tells you

Answer 21

how efficiently an enzyme

Question 22

how is catalytic perfection achieved

Answer 22

when a reaction rate is diffusion-controlled (10^8-10^9)

Question 23

When does Kcat/Km approach its “diffusion limit”

Answer 23

when the enzyme carries out catalysis every time a collision occurs between E and S

Question 24

Whar are the modes in which subtrate binds to a enzynme

Answer 24

1. Invoving a ternary complex
2. No ternary complex

Question 25

Which reaction modes does enzyme & substrate bind in random order or order

Answer 25

Ternary complex

Question 26

Which reaction follows a ping-pong mechanism

Answer 26

no ternary complex

Question 27

What is the difference between ordered and ping pong

Answer 27

1. the product is removed individually in Ping-pong mechanism
2. the enzyme conformation is changed as product is removed so E’ in ping-pong

Question 28

What does binding of a modulator do the substrate unit

Answer 28

it changes the conformation of the substrate, making it more active

Question 29

What is the advantage of inhibiting the first enzyme in a pathway

Answer 29

because it is allosterically regulated by final product of the pathway allowing feedback inhibition