lecture 6+7 Flashcards by Aneeka Phadnis

mitochondrial proton gradient

proton-motive force- potential energy for ATP synthesis

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electric transport chain & ATP synthesis

chemical potential ∆ph (inside alkaline)
->ATP synthesis driven by proton-motive force
-> electric potential ∆psi (inside negative)

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electron transport and oxidation phosphorylation

capture the energy in the redox potential of NADH and FADH2

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coupling depends on

-sequential redox reactions that pass electrons from NADH to O2
-the compartmentalization of these reactions in the mitochondrion
-the generation of a proton gradient from the above

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energy from glucose

is used to produce ATP

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2 ways ATP is produced

-substrate level phosphorylation
-oxidative phosphorylation

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electron transport

electrons carried by reduced coenzymes are passed through a chain of proteins and coenzymes
-drives the generation of a proton gradient across the inner mitochondrial membrane

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oxidative phosphorylation

the proton gradient runs downhill to drive the synthesis of ATP

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electrons pass

from electron donors to acceptors

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each subsequent electron acceptor

“wants” the electron more than the previous acceptor

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E°’ = standard reduction potential

A measure of how easily a compound can be reduced

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the more positive the standard reduction potential

the more the compound “wants” electrons

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in the ETC

carrier function is in the order of increasing reduction potential

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electrons move spontaneously

from carriers of low E°’ to carriers of higher E°’

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electrons flow through

a series of membrane-bound carriers

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four groups: complexes

includes integral and peripheral membrane proteins
use metal containing prosthetic groups or flavins to carry electrons

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Ubiquinone

a lipid-soluble carrier molecule

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Coenzyme Q/benzoquinone

lives in mitochondria membrane

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isoprenoid side chain

hydrophobic anchor

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for coenzyme Q to complete reduction it requires

2 electrons and 2 protons
(gets them from matrix)

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Q shuttles electrons from

complex I and II to complex III

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electron carrying groups

heme prosthetic groups(cytochromes), iron-sulfur groups(complexes I-III)

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protein complex

includes FMN and Fe-S centers

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electrons flow:

NADH - FMN
FMNH2-Fe3+
Fe3+-Fe2+

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electrons ultimately

shuttled to Q

energy of electron transfer

used to pump 4 H+

complex 1

NADH -dehydrogenase

complex 2

succinate dehydrogenase

succinate + FAD

fumerate + FADH2

Complex III:

Ubiquinone:Cytochrome C reductase

electron flow

ubiquinone to cytochrome C

oxidation of one QH2

moves 4+ across the inner mitochondrial membrane

complex 4

uses the energy of reduction of O2 to pump one H+ into the intermembrane space for each electron that passed through

4 Cyt C(red) +8 H+n +O2

4 Cyt C(oxi) +4 H+p + 2 H2O

it takes 2 NADH and uses 4 H+

to reduce one O2

for one pair of electrons

creates electrochemical gradient for protons to flow down and drive ATP synthesis

NADH 10 H- pumped

3 ATP

FADH2 6 H+ pumped

2 ATP

ETC inhibitors

rotenone,antimycin A ,cyanide

ATP synthase

protons move passively back into the matric through this. special transmembrane protein using electrochemical gradient

Complex V (atp synthase)

a multisubunit transmembrane protein

two functional units of atp synthase

F1 and F0

water-soluble peripheral membrane protein complex

generates 1 ATP

for every 3 protons through the complex

F0: transmembrane proton core

3 subunits:ab2c10-12

b subunit

stabilizes F1

C subunit

made up of small hydrophobic a-helices arranged in concentric circles

what causes the rotation of the c subunit

protons flow through c pores

F1 synthase structure

alternating alpa and beta subunits around a central gamma subunit

one domain of gamma forms central shaft

second domain associates with beta subunits

Three interacting catalytic beta subunits

each with a different conformational state

beta-adp

not catalitically active, binds adp and p

beta -atp

catalytically active, binds atp

beta empty

low affinity for adp or atp

free energy generated with proton movement is harnessed

to interconvert the conformation states to make and release ATP

conformational changes are

driven by the rotation of the rotor(c and gamma subunits) relative to the alpha beta subunits

3H+

for every 120 turn

conversion of beta-ADP to beta-ATP

synthesis of atp

conversion of beta -ATP to beta-ADP

release of ATP

when one beta subunit assumes beta empty

one neighbor assumes beta-adp one neighbor assumes beta atp

one complete rotation of gamma

causes each of beta to assume all 3 conformations 3 ATP FOR 360°

actin filament "jumps" in 3 steps of 120 moves in one direction

supports 3-stage binding change model

cellular respiration: the payoff

yield: an average of 3 atp per nadh; 2 ATP per FADH2

anaerobic fermentation

only 2 ATP/glucose

isolated mitochondria

O2 electrodes buffer assayed for ATP

need both a source of electrons(succinate) and ADP+P

to get respiration and atp synthesis

what blocks atp synthesis

venturicidin & oligomycin H+ build up but soon energy to pump H+ against gradient exceeds energy of ETC

uncouplers such as DNP can carry protons from P to N side

this dissipates the H+ gradient so etc begins again thus can etc without ATP synthesis

electron transport can be uncoupled from atp synthesis

2,4-dinitrophenol very hydrophobic, dissociable proton can carry H+ across inner mitochondrial membrane (destroys H+ gradient)

occurs in brown fat:

many mitochondria and cytochromes

oxidation of NADH uncoupled from ATP synthesis

energy of ETC is released as heat (found in newborn mammals)

pore protein called thermogenin

allows protons to flow down gradient and release as heat

lecture 6+7 Flashcards

(72 cards)