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Biochem 385 Unit 1 > Lecture 10: ETS > Flashcards

Lecture 10: ETS Flashcards

1
Q

What does ETS do?

A

convert redox nrg to PROTON MOTIVE FORCE

oxidation of NADH and FADH2 couped with reduction of water and oxygen

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2
Q

Chemoisomotic Theory

A

energy from redox (or light) coupled with electron transfer. move protons across membrane

ESTABLISH PROTON GRADIENT
source of electrochem energy

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3
Q

Chemiosmotic theory overview

A

oxidize NADH and FADH2 by ETS to link redox nrg to ATP synth

outward pumping of H+ thorugh 3 complexes

proton flow back down gradient through ATP synthase complex

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4
Q

inner mitochondrial membrane permiablity

A

impermable to ions

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5
Q

why do protons flow down gradient?

A

chemical gradient

electric gradient

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6
Q

complex one pumps

A

4 protons

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7
Q

complex three pumps

A

4 protons

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8
Q

complex 4 pumps

A

2 protons

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9
Q

when protons moved from matrix to intermembrane space…

A 
chemical potential (different pHs)
electrical potential
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10
Q

ATP synthase

A

driven by proton flow

ads a phosphate to make ATP

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11
Q

protons flow…

A

out through ETS (makes the gradients)

in through ATP synthase

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12
Q

Z in the equation

A

charge on molecule being transported

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13
Q

F in the equation

A

Faraday constant

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14
Q

The change in pH in mitochondria vs. chloroplasts

A

only about 25 fold in mitochondrial, pH difference makes much less change than MEMBRANE POTENTIAL DIFFERENCE

in chloroplasts: change in pH conttributes to delta G hugely! its about 1000 fold difference

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15
Q

If the delta G for transporting 1H+ across the membrane is 21.8kJ/molm what is the source of NRG for the mitochondria?

A

the redox reaction of NADH and FADH2

slide 9

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16
Q

What does ETS/oxidative phosphorylation accomplish for cell

A

generates 28 of 32 ATP from glucose catabolism

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17
Q

UPC

A

uncoupling protein

short circuts ETS and produces heat for thermoregulation

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18
Q

key enzymes

A

NADH dehydorgenase (1)
ubiquionse-cytochrome c oxioreductase (3)
cytochrome c oxidase (4)
ATP synthase

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19
Q

electrons flow spontaneouly…

A

from compounds with low reduction potential to compounds with high reduction potential. THINK PHYSICS!

less negative is more favorable?

20
Q

electrons start from

A 
NADH
to complex one (with FMN)
to coenzyme Q (ubiqinone)
to complex 3
to cytochrome C
to complex 4
end up on water
21
Q

how many protons per NADH pumped through complex 1?

A

4! 4 go through complex 1

so think about glucose, how many NADH per glucose?

22
Q

how many protons per NADH through complex 3?

A

4!

23
Q

cytochrome C

A

carries electrons from complex 3 to complex 4

24
Q

how many protons per NADH through complex 4?

A

2!

25
Q

how many protons come from a NADH molecule

A

10

26
Q

how many protons from an FADH2 proton

A

6!

27
Q

where to electrons go after complex 4?

A

they land on water

28
Q

What about complex 2???

A

It doesn’t pump protons

This is where elctrons from FADH2 enter the ETS!

29
Q

why does NADH give rise to more protons than FADH2????

A

b/c the electrons of FADH2 enter at complex 2
they bypass compound 1
that means they have 4 less protons!

30
Q

why does FADH2 even exist?

A

carries electrons that come from places besides the citrate cycle

31
Q

How are protons physically pumped?

A

2 ways:

1) Redox Loop Mechanism (complex 3)
2) Proton Pump mechanism (complexes 1 and 4)

32
Q

Redox Loop Mechanism

A

complex 3: Q cycle
electrons transferred from 1 molec to another
when electrons enter the protein, protons and electrons are sent in different directions

electrons end up on second molec
protons end up in intermembrane space

33
Q

Proton Pump mechanism

A

electrons transferred from one molec to another
this drives conf changes in protein, which changes affinity of amino acid side chains for proteins (changes whether proton is bound or released)

changes pKa values

this accomplishes directional movement of proton flow

slide 15

34
Q

Complex 1

A

where electrons from NADH enter ETS
huge, electrons flow through it to various electron carrying sites within it

transferes e- from NADH to ubiquinone (Q), making QH2 complex

4 protons from matrix to intermembrane space (per NADH)

35
Q

Iron Sulfer clusters

A

can form a structure that connects cistine residues?

WORK AS ELECTRON CARRIERS
lots in complex 1

36
Q

Complex 2

A

IS succinate dehydrogenase (citrate cycle: this reaction from the CC actually happens at this location)

where electrons from FADH2 enters, they are sent to Q to form QH2 also
other enzymes can also take these enzymes into the ETS

NOT A PROTON PUMP

37
Q

note about ubiquinone

A

each QH2 molec can take 2 e-

38
Q

Complex 3

A

transfers e- from QH2 to cytochrome c (which go from C3 to C4)
ONE AT A TIME
Q cycle!
translocates 4 H+ from matrix to intermembrane space per QH2

39
Q

cytochromes

A

small heme containing molecs
take e- from complex 3 to complex 4
has 2 diff sites for binding ubiquinonse

40
Q

Q cycle

A

Part of complex 3
mobile e- carier and a transformer

can carry 1 or 2 e-

converts 2e- transport system to ONE e- transport system (used by C 1 and 2)

why??? Cytochrome C only carries 1e- at a time

NET OXIDATION: 1 QH2 molec (2 get oxidized, but one gets reformed)

41
Q

4 steps of the Q cycle

A

2 binding cytes of QH2 (1 closer to intermembrane (1) space, one closer to matrix(2))

at 1; e- and protons separated
goes to 2, gets one e- back (the other goes to cytochrome C)

send in another QH2. same thing happens, but the e- that goes back to the OLD QH2 molec. SO THE FIRST QH2 MOLEC IS REFORMED!

SLIDE 21 SO MUCH SLIDE 21

42
Q

cytochrome C

A

transports ONE electron at a time from C3 to C4

has an iron

43
Q

Complex 4

A

happens 1 at a time!
2 cytochrome C molecs per 2 e-
e-s go through different sites, conf changes happen
as conf changes, protons pumped out
2 protons move from matrix to intermembrane space per 2 cytochrome c’s (e-s end up on water)

44
Q

BOOKKEEPING!

A

start with 2e- per NADH
translocation of 10 protons from matrix to intermembrane space
this sets up proton gradient (so outside is postive, higher pH)
ATP synthase
takes about 3 protons to make an ATP
then 1 more proton to move ATP because we need to move inorganic phospate into the matrix (its negative, so is the place it needs to be)
(so we do this by trading ADP and Pi for ATP, ADP can move in on its own, but Pi needs energy b/c its accross its conc gradient)

45
Q

how many ATP from each thing?

A

1 NADH gives 2.5 ATP
so 2 NADH makes 5ATP
1 FADH2 makes 1.5 ATP
so 2 FADH2 makes 3 ATP

how to get this? take the protons pumped and divide by 4!

46
Q

why only 32 and not 38 ATP made per molec?

A

BECAUSE WE HAVE TO USE A PROTON TO MOVE ATP OUT

Biochem 385 Unit 1 (13 decks)

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