enzymes + enzyme kinetics

Question 1

What is S⟶P?

Answer 1

from substrate to product

Question 2

What is G‡?

Answer 2

free energy to overcome transition state

Question 3

What is ∆G‡ₛ⟶ₚ?

Answer 3

energy to get from substrate to product

Question 4

What is ∆G‡ₚ⟶ₛ?

Answer 4

energy to get from product to substrate

Question 5

What is ∆G’ᵒ?

Answer 5

standard free energy

Question 6

enzyme

Answer 6

a catalyst that lowers activation energy but is not used up in reaction

Question 7

cofactor

Answer 7

an inorganic ion/coenzyme required for enzyme activity

Question 8

What are the classes of enzyme classification?

Answer 8

1) oxidoreductases
2) transferases
3) hydrolases
4) lyases
5) isomerases
6) ligases

Question 9

oxidoreductases

Answer 9

oxidation/reduction (transfer of electrons)

Question 10

transferases

Answer 10

transfer of functional groups

Question 11

hydrolases

Answer 11

breaking of single bonds through addition of water (hydrolytic cleavage)

Question 12

Give an example of hydrolytic cleavage.

Answer 12

transfer of functional groups to water

Question 13

lyases

Answer 13

breaking of bond(s) by means other than hydrolysis + oxidation, often forming a new double bond/ring structure

Question 14

isomerases

Answer 14

rearrangement of groups (producing isoforms)

Question 15

ligases

Answer 15

formation of new bond

Question 16

zymogen

Answer 16

inactive form of enzyme

Question 17

holoenzyme

Answer 17

apoenzyme + cofactor

Question 18

lock-and-key

Answer 18

active site of unbound enzyme is complimentary to shape of substrate

Question 19

induced fit

Answer 19

active site complimentary to shape of substrate only after substrate binds (enzyme changes shape when substrate binds)

Question 20

collagen

Answer 20

major structural components of connective tissues

Question 21

specificity

Answer 21

always cut in the same place

Question 22

SDS-PAGE

Answer 22

separates proteins based on their mass (lighter proteins travel further than heavier proteins)

Question 23

How can collagenolysis be assessed?

Answer 23

SDS-PAGE

Question 24

What are the factors affecting enzyme activity?

Answer 24

1) pH
2) temperature
3) [substrate]
4) presence of inhibitors

Question 25

How does pH affect enzyme activity?

Answer 25

pH outside optimum range will change conformation + may denature enzymes

Question 26

How does temperature affect enzyme activity?

Answer 26

1) affects kinetic energy of substrate + enzyme 2) determines frequency of substrate + enzyme interaction 3) increases rate of reaction until enzyme is saturated

Question 27

How does [substrate] affect enzyme activity?

Answer 27

1) determines frequency of substrate + enzyme interaction | 2) increases rate of reaction until enzyme is saturated

Question 28

coenzyme

Answer 28

organic (non-metal) cofactor required for action of certain enzymes

Question 29

V₀

Answer 29

initial velocity

Question 30

Vₘₐₓ

Answer 30

maximum velocity of enzymatic reaction when binding site is saturated with substrate

Question 31

Kₘ

Answer 31

1) substrate concentration at which enzyme-catalysed reaction proceeds at 1/2 maximum velocity 2) inverse measure of substrate's affinity for enzyme

Question 32

rate, v =

Answer 32

1) ∆[P]/∆t (product formation | 2) -∆[S]/∆t (substrate depletion)

Question 33

ES

Answer 33

enzyme-substrate complex

Question 34

EP

Answer 34

enzyme-product complex

Question 35

What is the following equation simplified? | E + S ⇌ ES ⇌ EP ⇌ E + P

Answer 35

E + S ⇌ ES ➝ E + P

Question 36

Why is the initial velocity the maximum rate?

Answer 36

enzyme + substrate concentrations are at highest

Question 37

What is the relationship between {S] and rate?

Answer 37

as [S] increases, enzyme becomes saturated with substrate + rate reaches Vₘₐₓ

Question 38

Michaelis-Menten equation, V₀ =

Answer 38

Vₘₐₓ[S]/Kₘ + {S]

Question 39

reversible/irreversible inhibitors

Answer 39

depends on strength of bond between inhibitor + substrate

Question 40

What are the types of inhibitors?

Answer 40

1) reversible 2) irreversible 3) competitive 4) uncompetitive 5) non-competitive

Question 41

What happens in the presence of a competitive inhibitor?

Answer 41

1) Vₘₐₓ unchanged (sufficient [S] out-competes inhibitor) | 2) Kₘ increased (reduced binding affinity as ES can dissociate + EI form, due to competition)

Question 42

What happens in the presence of an un-competitive inhibitor?

Answer 42

1) Vₘₐₓ reduced (some unproductive ESI complex will always be present) 2) Kₘ reduced (formation of ESI to maintain equilibrium, more S binds to E + lower [S] required)

Question 43

What happens in the presence of a non-competitive inhibitor?

Answer 43

1) Vₘₐₓ reduced (like un-competitive inhibitor) | 2) Kₘ unchanged (no change in position of equilibrium)

Question 44

What does less signal mean on a spectrophotometer?

Answer 44

more product

Question 45

What does more signal mean on a spectrophotometer?

Answer 45

less product

Question 46

Why are spectrophotometers used?

Answer 46

to measure product formation

Question 47

What does a small Kₘ indicate?

Answer 47

high affinity (rate will approach Vₘₐₓ more quickly)