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Biochem 385 Unit 1 > Lecture 8: Metabolic Redox Reactions > Flashcards

Lecture 8: Metabolic Redox Reactions Flashcards

1
Q

reduction potentials are a measure of

A

electron affinity

E

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2
Q

electrons flow…

A

from reductants to oxidants

toward compinds with higher (more pos) E values

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3
Q

Pyruvate dehydrogenase (PDH)

A

converts pyruvate to acetyl-CoA

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4
Q

acetyl-CoA is used for…

A
  1. complete oxidation by citrate cycle

2. fatty acid synthesis

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5
Q

how is energy avalible from ReDox reactions?

A

based on nrg avalible from redox reactions

due to differences in electron affinity of 2 compounds

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6
Q

coupled reactions

A

2 half reactions

oxidation reaction and reduction rxn

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7
Q

oxidant

A

will accept electrons

are REDUCED

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8
Q

reductants

A

donate electrons

are OXIDES

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9
Q

Fe-Cu redox reaction

A

occurs in cytochrome c oxidase

in electron transport system

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10
Q

aerobic resiration transfer…

A

electrons from GLUCOSE to O2 (oxygen)

to form CO2 and H2O

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11
Q

see slide 5

A

see slide 5

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12
Q

who owns the electrons in a CH bond?

A

Hydrogen is less electronegative than carbon!

so carbon owns the electrons

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13
Q

Who owns electrons in an OH bond

A

oxygen is more electronegative than carbon!

Oxygen owns the electrons

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14
Q

NAD+ and NADH

A

reduction of NAD+ to NADH

transfer of hydride ion (:H-)
-contains 2e- and 1 H+
and release of proton (H+)

NAD+ + 2e- + 2H+ NADH+ H+

electrons added as a pair associated with a hydride ion (proton gets lost)

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15
Q

FAD and FADH2

A

FAD reduced by SEQUENTIAL ADDITION of one Hydrogen (1e- and 1 H+) at a time to get fully reduced FADH2

differs from NADH b/c e- can be added one at a time

FAD + 1e- +1H+ FADH +1e- + H+FADH2

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16
Q

hydrogen half reaction

A

0 value

what we compare everything else to

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17
Q

electron affinity measured by…

A

comparing it to hydrogen half reaction

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18
Q

E^0’

A

Standard

under same standard conditions as deltaG^0’

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19
Q

review how to read table on slide 9!

A

review how to read table on slide 9!

hydrogen half reaction is in middle!

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20
Q

table is read…

A

standard reduction potentials are written in the direction of reduction reaction

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21
Q

facts about E^0’

A

subtract reduction potential of donor from acceptor
proportional to standard free energy change
A CONSTANT
(it is favorable when value is POSITIVE)

22
Q

n in G^0’ / e^0’ equation means…

A

NUMBER OF ELECTRONS

23
Q

tip for doing reduction potential reactions

A

keep everything as reduction (don’t flip signs) and SUBTRACT donor from acceptor
(can flip reaction to show oxidation and change sign of E^0’, but that’s harder)

24
Q

review/ listen to slide 11

A

review/ listen to slide 11

25
Q

if you know ACTUAL CONCENTRATIONS of oxidants and reductants, use….

A

Nernst equation

26
Q

Pyruvate converted to acetyl-CoA by…

A

Pyruvate dehydrogenase complex (PDH)

27
Q

acetyl-CoA and the citrate cycle

A

metabolized to convert redox nrg to ATP

Oxidative phosphorylation

28
Q

acetyl-CoA used as a form of stored energy

A

conversion to fatty acids

go to adipocytes as triglycerides

29
Q

pyruvate dehydrogenase complex

A

made up of 3 subunits E1 (22 of them) E2 (60) and E3(6)

lots of active sites (60)
so 1 enzyme can do this reaction a bunch of times simulatneously

30
Q

PDH coenzymes

A

TPP attached to E1
lipoamide attached to E2
FAD covalently bound to E3

31
Q

see slide 16 for how PDH works

A

see slide 16 for how PDH works

32
Q

PDH step 1

A

E1 loses CO2, attach acetyl group of pyruvate to E1

33
Q

PDH step 2

A

in PDH subunit, theres a lipoamide group with a disulfide bond

acetyllipoamide made when disulfide bond reduced

that makes acetyl Co-A b/c acetyl groupd transfered onto

left with oxidized molec

34
Q

transfer of the acetyl group in PDH

A

take it off pyruvate
transfer on to TPP
transfer onto lipoamide
put onto Co-a to make acetyl CoA

35
Q

PDH step 3

A 
regenerating for turnover
use FAD that is attached to E3
oxidized molec left from 2
reduce FAD, redoxidzes the thing left from 2
use NAD to reoxidze FAD
we get reduced NADH
36
Q

REVIEW SLIDE 17

A

REVIEW SLIDE 17

reaction and red questions

37
Q

what comes out of the PDH reaction

A

pyruvate + CoA + NAD+—–> Acetyl CoA + CO2 + NADH

38
Q

is the PDH reaction reversible?

A

NO

39
Q

what does the PDH complex do?

A

catalyzes oxidative decarboylation of pyruvate to make CO2 and acetyl-CoA

40
Q

Arsenite

A

inhibitor of lipoamide

ingestion can lead to death b/c it irreversibly blocks ability of lipoamide-containing enzymes like PDH

found in arsenic

41
Q

REVIEW SLIDE 19

A

REVIEW SLIDE 19

42
Q

NAD+

A

redox
transfer of hydride ion
from B3

43
Q

FAD

A 
redox
transfer of electrons (2) (H)
from B2 (riboflavin)
44
Q

CoA

A

acetyl group transfer
from B5 (panthothenic acid)
carrier molec for acetate units to make acetyl-CoA

45
Q

TPP

A 
aldehyde transfer
from B1 (thiamine)
46
Q

lipoamide

A

acetyl group transfer

not a vitamn

47
Q

biocytin

A

carboxyl group transfer

from Biotin

48
Q

Catabolic redox reactions

A

use redox pair NAD+/NADH

49
Q

the “+” in NADH

A

does NOT refer for charge of NAD moelc

only refers to charge on ring nitrogen in oxidized state

50
Q

anabolic redox reactions use

A

NADP+/NADPH

51
Q

Acetate

A

covalently attached to CoA through activated thiosester bond

requires high deltaG^0’ values

Biochem 385 Unit 1 (13 decks)

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