Chapter 6: Section 6.3

Question 1

determines the rate of reaction & how it changes in response to changes in experimental parameters

Answer 1

enzyme kinetics

Question 2

what affects the rate of enzyme-catalyzed reactions?

Answer 2

substrate concentration [S]

Question 3

concentration of substrate changes during _____ reaction as substrate converts to ______

Answer 3

in vitro; product

Question 4

what is V0?

Answer 4

initial rate/ initial velocity

Question 5

when can substrate be regarded as constant?

Answer 5

when only the beginning of the reaction is monitored and over a small period where a small % of the substrate is converted to product

Question 6

initial velocity can be seen as a function of ______

Answer 6

substrate concentration [S]

Question 7

low concentrations of V0 ______ with increase in _____

Answer 7

increases; [S]

Question 8

what happens when there is a high [S]?

Answer 8

V0 increases by smaller and smaller amounts in response to increase in [S]

Question 9

point reached beyond increases in V0 are small as [S] ____

Answer 9

increases

Question 10

V0 region is close to ______

Answer 10

Vmax

Question 11

enzyme that catalyzes the reaction S<>P is present at a concentration ______ to catalyze the reaction at ____ of 1 micrometer per minute

Answer 11

sufficient; Vmax

Question 12

what is Km?

Answer 12

Michaelis constant
0.5 micrometer

Question 13

rate ____ as substrate converts to _____

Answer 13

declines; substrate

Question 14

tangent to each curve taken at time equals _____ defines the initial velocity of each reaction

Answer 14

zero

Question 15

What is the ES complex?

Answer 15

ES complex is the state in, which the active site of the enzyme is non-covalently bound to the substrate molecule(s)

Question 16

What does the 1st enzyme do?

Answer 16

enzyme combines reversibly with its substrate complex in fast reversible step E+S k><k-1ES

Question 17

What does the 2nd enzyme do?

Answer 17

ES complex breaks down in a slower second step to yield free enzyme and reaction product P: ES k2><k-2 E+P

Question 18

initial velocity ignores _____ reaction

Answer 18

reverse

Question 19

slope = ?

Answer 19

delta initial velocity/ delta [S]

Question 20

what does a slower second reaction limit?

Answer 20

It limits the rate of overall reaction

Question 21

what is the overall rate proportional to?

Answer 21

proportional to the concentration of species that reacts in the 2nd step > ES

Question 22

Model mechanism

Answer 22

E+S > ES > E+P

Question 23

Step 1 of the mechanism

Answer 23

enzyme-substrate complex (ES) - rapid bimolecular step

Question 24

Step 2 of the mechanism

Answer 24

-ES forms product
-rate-limiting step
-net rate: combines rate constants from all steps [E] & [S]

Question 25

Characteristics of the enzyme inside of the cell

Answer 25

the enzyme concentration is low and limiting

Question 26

enzyme kinetics experiments hold ____ constant

Answer 26

[enzyme]

Question 27

equation of [substrate]

Answer 27

[substrate]tot = [S] + [ES] = [S]

Question 28

equation of rate

Answer 28

V = k = [ES]

Question 29

what happens when there is high [S]?

Answer 29

-the enzyme is saturated with substrate
-the reaction is zero order w/ respect [S]: ES _ E + P

Question 30

what is pseudo?

Answer 30

first-order reaction overall since the rate depends on # of active sites
-only more enzymes increase the reaction rate

Question 31

what forms of enzyme exist when there a reaction where the enzyme is catalyzed?

Answer 31

2 forms
-free/ uncombined form E
-combined form ES