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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
what is the x- intercept of burk plot
-1/Km
26
y-intercept of burk plot
1/Vmax
27
what is the slope of burk plot
Km/Vmax
28
What are the 3 types of reversible inhibition
1. competitive 2. uncompetitive 3. noncompetitive ( mixed) inhibition
29
Competitive inhibition
-structurally similar to S-> compete with S for active site bonding - Km increases but Vmax stays the same
30
Uncompetitive inhibition
- binds only ES (not to the active site) but not to the free enzyme - both Km and Vmax change - does not change the slope
31
noncompetitive
- 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
Feedback inhibition
- inhibited by the final product - homeostasis: balancing product with cells need
33
Product inhibition
- Inhibited by an immediate product
34
Modulator binding to enzyme->
different shape
35
Conformations change in one subunit -> ...->
change in other subunits in complex-> other subunits affinity to S
36
most allosteric effectors affect only ... but some change...
Km: Vmax
37
What involves electron transfer between 2 molecules
Oxidation -reduction
38
oxidized is
loos of electron
39
Reduction is
gain of electron
40
biological oxidation loses...
2H + 2e or gaines Oxygen
41
Biological reduction gains
2H+2e or loose Oxygen
42
What is the most oxidized form of carbon found in living organisms
CO2
43
Where does glycolysis take place
cytosol
44
How much ATP do you spend in step 1 of glycolysis
2ATP
45
ATPs are consumed in steps... by...
1 and 3 by hexokinase and phosphofructokinase
46
How many ATPS are yieled in step 2
4 ATP
47
in step 2 two GAP ->
2 pyruvate
48
what steps are ATP synthesized in and by what enzymes
7 and 10 and by PGK and PK by substrate-level phosphorylation
49
What are the three control points
-Hexokinase (step 1) - Phosphofructokinase (step 3) - pyruvate kinase (step 10)
50
What inhbits Hekokinase
its product
51
PFK is inhibited by ...but activated by
ATP and citrate AMP
52
PK is inhibited by... by activated by
ATP and Acetly-CoA AMP and fructose-1, 6-biphosphate
53
Where does TCA take place
Mitochondrial matrix
54
Step 1 of TCA allosterically ...
inhibited
55
What acts as the intracyclic regulatory in step 1
Succinyl-CoA
56
what is the indicator of enegertic status in step one
NADH
57
what step is the 1st oxidative reaction in TCA
step 3
58
step 3 is inhibited by...activated...by
ATP and NADH ADP and NAD
59
does high or low ratio mean green light
high ratio
60
Step 4 is the...
2nd oxidative reaction
61
step 4 is actived by and inhibited by
AMP NAHD and Succinyl-CoA
62
was is oxidized and reduced in step 6 of TCA
Succinate FAD
63
what is substrate-level phosphorylation
phosphorylation of ADP into ATP forms a product containing a high-energy bond
64
Where does Oxidative phos. take place
ETC in the mitochondria
65
What is reduction potential
tendency of a give reacting species to gain e when paired with a standard
66
Positive reduction potential means
tendency to attract/ accept en
67
negative reduction potential
give up e
68
positive potential is
reduced
69
negative potential is
oxidized
70
e always spontaneously flow from half-rxn with
more neg tendency to more pos. tendency
71
O state is
open inactive cannot bind to ADP
72
L state is
loose binding inactive
73
T state
tight binding active
74
Step 1 in ATP synthase
ADP+Pi bind to L site
75
Step 2 ATP synthase
L-> T T->O O->L
76
Step 3 ATP synthase
ATP is released from O

Bio Chem (3 decks)

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