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Bio Chem > Final exam ( enzymes and mechanismd) > Flashcards

Final exam ( enzymes and mechanismd) Flashcards

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1
Q

Holoezyme (active) is

A

apoenzyme (inactive) + cofactor

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2
Q

What are two type of cofactors

A

metal ions (inorganic)
coenzymes (organic)

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3
Q

what are the two subgroups in coenzymes

A

cosubstrates: loosely bound, cycle on and off
Prosthetic groups: tightly/covalenty bound

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4
Q

What are the 5 catalytic mechanism

A
  1. acid-base
  2. covalent
  3. metal ion
  4. proximity and orientation effect
  5. preferential binding of transition state (ES complex)
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5
Q

explain acid-base

A

partial proton donation ( general acid catalysis) or abstraction (general base catalysis)

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6
Q

how does covalent catalysis take place

A

via transient formation of covalent E-S intermediate

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7
Q

Explain metal ion catalysis

A

-Enzymes that require metal ions for catalysis

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8
Q

What are metalloenzymes

A

-metal ion catalysis
- tightly bound, usually transition metals

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9
Q

what are metal- activated enzymes

A

loosely bound metal from solution, alkaline

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10
Q

Explain proximity and orientation effect

A

-binding to E forces substrate to orient in a certain way -> rotational, translational motions cease-> active groups face each other -> reaction

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11
Q

explain preferential binding

A
  • affinity for E binding ES» E+S or E+P
  • Time at transition state increases -> ES increases-> chance to form product increases
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12
Q

what is given by its exponent

A

Reaction order

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13
Q

what is Km ( michealis constant)

A

-enzyme binding affinity

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14
Q

higher Km means

A

weaker affinity

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15
Q

What does Vmax mean

A

Maximum rate of the reaction

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16
Q

What is Vmax related too

A

Kcat and [Et] by Vmax

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17
Q

Vmax=

A

Kcat[Et]

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18
Q

What does Kcat represent

A

-speed of catalysis
- measured product formation ( substrate turnover)

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19
Q

Higher Vmax =

A

higher max rate

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20
Q

Higher Kcat=

A

higher speed

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21
Q

Kcat/Km is a measure of

A

Catalytic efficiency of enzyme

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22
Q

V=

A

-VmaxKm/(Km+Km)
- 1/2* Vmax

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23
Q

When [s]=Km the rate is

A

half-maximal

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24
Q

what can the Lineweaver-burk plot show

A

can determine Km and Vmax graphically

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25
Q

what is the x- intercept of burk plot

A

-1/Km

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26
Q

y-intercept of burk plot

A

1/Vmax

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27
Q

what is the slope of burk plot

A

Km/Vmax

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28
Q

What are the 3 types of reversible inhibition

A
  1. competitive
  2. uncompetitive
  3. noncompetitive ( mixed) inhibition
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29
Q

Competitive inhibition

A

-structurally similar to S-> compete with S for active site bonding
- Km increases but Vmax stays the same

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30
Q

Uncompetitive inhibition

A
  • binds only ES (not to the active site) but not to the free enzyme
  • both Km and Vmax change
  • does not change the slope
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31
Q

noncompetitive

A
  • binds both E and ES (not in the active site)
  • changes the slope steeper
    -When K1=K’1
    - y-intercept moves up but x-intercept stats the same
    - Vmax decreases but Km stays the same
32
Q

Feedback inhibition

A
  • inhibited by the final product
  • homeostasis: balancing product with cells need
33
Q

Product inhibition

A
  • Inhibited by an immediate product
34
Q

Modulator binding to enzyme->

A

different shape

35
Q

Conformations change in one subunit -> …->

A

change in other subunits in complex-> other subunits affinity to S

36
Q

most allosteric effectors affect only … but some change…

A

Km: Vmax

37
Q

What involves electron transfer between 2 molecules

A

Oxidation -reduction

38
Q

oxidized is

A

loos of electron

39
Q

Reduction is

A

gain of electron

40
Q

biological oxidation loses…

A

2H + 2e or gaines Oxygen

41
Q

Biological reduction gains

A

2H+2e or loose Oxygen

42
Q

What is the most oxidized form of carbon found in living organisms

A

CO2

43
Q

Where does glycolysis take place

A

cytosol

44
Q

How much ATP do you spend in step 1 of glycolysis

A

2ATP

45
Q

ATPs are consumed in steps… by…

A

1 and 3 by hexokinase and phosphofructokinase

46
Q

How many ATPS are yieled in step 2

A

4 ATP

47
Q

in step 2 two GAP ->

A

2 pyruvate

48
Q

what steps are ATP synthesized in and by what enzymes

A

7 and 10 and by PGK and PK by substrate-level phosphorylation

49
Q

What are the three control points

A

-Hexokinase (step 1)
- Phosphofructokinase (step 3)
- pyruvate kinase (step 10)

50
Q

What inhbits Hekokinase

A

its product

51
Q

PFK is inhibited by …but activated by

A

ATP and citrate
AMP

52
Q

PK is inhibited by… by activated by

A

ATP and Acetly-CoA
AMP and fructose-1, 6-biphosphate

53
Q

Where does TCA take place

A

Mitochondrial matrix

54
Q

Step 1 of TCA allosterically …

A

inhibited

55
Q

What acts as the intracyclic regulatory in step 1

A

Succinyl-CoA

56
Q

what is the indicator of enegertic status in step one

A

NADH

57
Q

what step is the 1st oxidative reaction in TCA

A

step 3

58
Q

step 3 is inhibited by…activated…by

A

ATP and NADH
ADP and NAD

59
Q

does high or low ratio mean green light

A

high ratio

60
Q

Step 4 is the…

A

2nd oxidative reaction

61
Q

step 4 is actived by and inhibited by

A

AMP
NAHD and Succinyl-CoA

62
Q

was is oxidized and reduced in step 6 of TCA

A

Succinate
FAD

63
Q

what is substrate-level phosphorylation

A

phosphorylation of ADP into ATP
forms a product containing a high-energy bond

64
Q

Where does Oxidative phos. take place

A

ETC in the mitochondria

65
Q

What is reduction potential

A

tendency of a give reacting species to gain e when paired with a standard

66
Q

Positive reduction potential means

A

tendency to attract/ accept en

67
Q

negative reduction potential

A

give up e

68
Q

positive potential is

A

reduced

69
Q

negative potential is

A

oxidized

70
Q

e always spontaneously flow from half-rxn with

A

more neg tendency to more pos. tendency

71
Q

O state is

A

open
inactive
cannot bind to ADP

72
Q

L state is

A

loose binding
inactive

73
Q

T state

A

tight binding
active

74
Q

Step 1 in ATP synthase

A

ADP+Pi bind to L site

75
Q

Step 2 ATP synthase

A

L-> T
T->O
O->L

76
Q

Step 3 ATP synthase

A

ATP is released from O

Bio Chem (3 decks)

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