Enzyme kinetics - measure reaction rate

Question 1

kinetic energy

Answer 1

associated with movement through series of step

how effective it is on basis of how much it reduces ROR

Question 2

starting point - measuring in reaction with enzyme

Answer 2

measure change in [S] or [P] over time after adding E

Question 3

spectrophotometer

Answer 3

measures absorbance decrease in [S] or increase in [P]

Question 4

example of using spectrophotometer - yellow product

Answer 4

a yellow product - absorbs blue light
increase [P] = yellow appears over time
rate not constant - gradient = increase [P]/S = reaction velocity
shine blue light at 0s - 0 absorbance
enzyme add - over time blue light decrease as [P] increases

Question 5

v (velocity) units

Answer 5

mol/min or mol/s (katal)

Question 6

enzyme activity unit

Answer 6

μmol/min (IU)

Question 7

IU

Answer 7

international unit

Question 8

specific activity units

Answer 8

enzyme activity/ total amount of protein(mg)

μmol/min/mg or IU/mg

Question 9

mg

Answer 9

relating enzyme rate to amount of protein

Question 10

reaction progress

Answer 10

at constant equilibrium - rate = 0

Question 11

overall ROR

Answer 11

depend on kc and conc
A -> B
ks -> p[S] -> s[P] where A>B

Question 12

overall arrow of direction

Answer 12

increase [P] = arrow - bigger backwards

Question 13

arrow size balance

Answer 13

equilibrium - [P]>[S]

kc is smaller

Question 14

overall arrow of direction - conc - manipulated

Answer 14

increase [P] - push back reaction

amount of S and P increase - reaction at equilibrium is same

Question 15

comparing enzymes

Answer 15

turnover number
enzyme efficiency
enzyme potency

Question 16

turnover number

Answer 16

catalytic rate constant kcat - no.reactions/s

Question 17

enzyme efficiency

Answer 17

catalytic speed vs affinity - kcat/ Km

kinetic perfection - >1x10(8) - V limited by diffusion of S to E not E

Question 18

enzyme potency

Answer 18

how many times faster reaction with enzyme

Question 19

Briggs/Haldane assumption

Answer 19

[ES[ is constant is ES goes to P or S - equilibrium adjust

[S]»[P] therefore [S] is constant

Question 20

Michaelis constant equation

Answer 20

Km = (K-1 + Kcat) / K1

Question 21

Michaelis constant

Answer 21

E+S ES -> E+P

Question 22

E+S -> ES

Answer 22

K1

Question 23

ES -> E+S

Answer 23

K-1

Question 24

ES -> E+P

Answer 24

Kcat

Question 25

Michaelis-Menten curve - enzyme reaction

Answer 25

V = (Vmax x [S]) / (Km + [S])

Question 26

Vmax

Answer 26

find approximation on graph

Question 27

Km

Answer 27

1/2 Vmax -> E=ES

[S] at 1/2 Vmax

Question 28

line weaver-Burk plot - Vmax

Answer 28

1/2max when 1/[S] = 0

=Kcat x [E]

Question 29

low Vmax

Answer 29

saturating [S] -> unusual but S=ethanol

Question 30

Km

Answer 30

[s] gives half max rate of half of E are ES
low Km - high affinity for S
high - cell [S] - close to Km

Question 31

example methanol poisoning

Answer 31

ADH bind to any alcohol breakdown

= formaldehyde(toxic) - destroy molecules (biological) but ethanol (1mM) - methanol not broken because stronger affinity

Question 32

example isozymes

Answer 32

glucokinase (10mM of Km)
Hexokinase (0.2mM or Km) - stronger affinity
remain at normal blood level range
different enzyme same substrate

Question 33

Km definition

Answer 33

determines how active enzyme is at particular [S]