Oxidative Phosphorylation Flashcards
2,4-dinitrophenol is what class that prevents oxidative phosphorla?
uncoupler
mechanism fo action of 2,4-dinitrophenol
Discharges the pH gradient
2,4-dinitrophenol sx? use?
Marked increase in metabolism profuse sweating, collapse, death.
Formerly used for weight reduction
what class is Gramicidin?
Ionophores
what sit he mechanism of action of Gramicidin
Forms a membrane pore permeable to protons
what are the sx of Gramicidin
Antimicrobial at low concentration. High concentration is fatal
what class is valinomycin?
Ionophores
Valinomycin mechanism of action
A membrane soluble, diffusional carrier of K+
valinomycin sx?
fatal
Oligomycin is a ___
Phosphoryl- ation
Inhibitors
Oligomycin MOA?
Prevents use of the electrochem. grad. to drive ATP synthesis
sx of Oligomycin
Fatal
what are the Inhibitors of Electron
Transport? (5)
- Rotenone
- Amytal (barbiturates)
- Antimycin A
- CN-
- CO
Rotenone MOA
inhibits chain at 1st coupling site
Rotenone sx? uses?
sx – Nausea, vomiting, convulsions, death from respiratory paralysis.
use – Used in a topical ointment for treatment of chiggers. Also used as a poison for harvesting fish and as an insecticide
what meds Inhibits chain at 1st coupling site?
Amytal (barbiturates)
rotenone
Amytal (barbiturates) sx?
Nausea, vomiting, convulsions, death from respiratory paralysis.
(same as rotenone)
Antimycin A MOA
Inhibits chain at 2nd coupling site
Antimycin A sx? uses?
Fatal, used as fungicide and insecticide
CN- mOA
Inhibits chain at cytochrome a3, blocks
O2 binding by binding to FeIII
CN- sx?
Convulsions, unconsciousness, death from respiratory paralysis.
cyanide antidote
Antidote: nitrite and thiosulfate intravenously (oxidizes some hemoglobin to met
hemoglobin which binds CN-). Administer O2
what  Inhibits chain at cytochrome a3, blocks O2 binding by binding to FeII??
CN and CO
what does death from co result from?
interaction with hemoglobin before it can reach the respiratory chain.
sx of CO poisoning
Dizziness, vomiting, increase then decrease of pulse and respiration, collapse, death.
what to tx CO poisoning with
O2
Inhibitors of mitochon-
drial trans- port systems
 include (2)
Atractyloside Bongkrekic Acid
Mercurous salts
Mercurous salts sx
Muscle spasms, depression, death from kidney failure usually within a week of exposure.
Mercurous salts MOA
Inhibits Pi transport by
reaction with essential - SH
what were Mercurous salts formely used for?
treating syphilis
Atractyloside Bongkrekic Acid MOA?
Inhibits ADP/ATP transport. ATR. prevents binding
of ADP. B.A. prevents release of ADP
Atractyloside Bongkrekic Acid sx?
Convulsions of a hypoglycemic nature (logical, isn’t it?), collapse, death
Uncouplers uncouple ____ from phosphorylation
oxidation
The effect of uncouplers on respiratory control. Uncouplers stimulate ____ in the absence of ADP.
oxygen consumption
Uncouplers dissipate the proton gradient by providing an
alternate route for proton re- entry into the matrix
what happens in absence of a graident?
the synthase runs in reverse hydrolyzing ATP.
Properties of uncouplers?
weak acids, hydrophobic, delocalized charge
A natural ____ present in mitochondria of brown adipose tissue is involved in non-shivering thermogenesis and weight regulation
uncoupler
structure of the uncoupler protein in the mitocondria of brown adipose tissue. what regulates it?
The uncoupler protein contains a proton pore which is under careful hormonal regulation
Oligomycin blocks ___
ADP
Oligomycin blocks ADP- but not
uncoupler- stimulated respiration.
Oligomycin blocks proton movement through ___
FoF1
why does respiration slow with olgiomycin?
protons no longer reenter the matrix through FoF1.
Uncouplers stimulate respiration, but ____.
no ATP is made.
A natural phosphorylation inhibitor (the inhibitor protein) protects against
rapid ATP hydrolysis during ischemia
when does the natural phosphorylation inhibitor bind to FoF1? how?
in the absence of O2, the pH of the matrix space drops and the inhibitor protein is protonated changing its conformation to a form that binds tightly to FoF1.
Oxygen consumption measurement showing effect of cyanide
what is blocked?
ADP- and uncoupler-stimulated respiration are blocked.
In heart mitochondria, the response to cyanide is
the inhibitor protein will bind to the ATP synthase to inhibit ATP hydrolysis.
(like with ischemia)
Cyanide acts by competing with O2 for binding to(3)
the heme a3 iron and CuB.
Unlike O2, CN- cannot accept ___
electrons
The basic premise of the chemiosmotic theory is that a ____ gradient is a required intermediate in coupling the exergonic redox reactions to the endergonic synthesis of ATP
delocalized electrochemical
Mitchell proposed a ___ mechanism for generating the gradient called: “Mitchell’s Loops”.
direct coupling
the net result of a mitchells loops like Q
two protons have been transported out of the mitochondrion against an electrochemical gradient.
Mitchell’s proposed Loops cannot function in
cytochrome oxidase, since tehre is no hyodrgen donor/acceptor
The principle of pumps is that proton transport is coupled to ____ indirectly through protein conformational changes
exergonic redox reactions
The FoF1-ATP synthase is now recognized to be a tiny molecular motor. Instead of being driven by a current of electrons it is driven by
current of protons
Shuttles of reducing equivalents from glycolytic NADH to the Respiratory Chain.
(1) Glycerol phosphate shuttle
(2) Malate/aspartate shuttle
ADP/ATP and Pi Translocases
involves One ADP moves in and one ATP moves out with the net exit of
one negative charge (electrogenic).
One P - and one H+ move in with a net loss of one H+
2 predictions by mitchell
predictions
- membranes impermeable to protons
- electrochemical gradient exists
2 things are needed for mitchells loops to work (q cycle)
alternate between electron donors
and hydrogen donor acceptors
and you are going to alter which
side of the membrane reduction and
oxidation occur
in mitchells loops, 2 protons are moving ___. this is driven by ___.
against the gradient
driven by redux reactions
stoichimotery of mithcells loops?
2H+/e- or 4H+/2 e-.
On the inside surface, an iron-sulfur center of a dehydrogenase and Cyt bh donate 1 e- each to___
Q
Q must also pick up ___ from the aqueous inside phase
after getiting electron from iron-sulfur center of a dehydrogenase and Cyt bh
2 H+
after Q picks up 2 electrons and 2 ptorons it then must ___ to be oxidized
diffuse outside surface to be oxidize
after QH2 2 electorn complex diffuses to outside surface what happens?
1 electron is rtansferred to iron sulfur center and another to cyt b
once Q gets rid of its electrons..
loses both hydrogens to become fully oxidized
then diffuses back inside to begin next cycle
a hydrogen acceptor (i.e., H+ + e-) such as Q is reduced on the inside surface of the inner mitochondrial membrane by electron donors that can supply
electrons but not the required protons
protons are received from the matrix
once Q is reduced, the hydrogen donor can move to be
oxidized
where does Q dump the protons?
in the intermembrane space
explain the rotatry wheel of atp synthease
A H+ enters a channel and hops on to c subunit
c subunit rorates until the proton is aligned with a second channel
- c rotary wheel is anchored to γ, when c subunits rotate realtive to a, γ is forced to rotate relative to the catlaytic subunits
- the drive is protons moving down gradient is coupled with need to break atp off, allowing atp to be broken off
The ___synthase is now recognized to be a tiny molecular motor.
FoF1-ATP
what are the only known proton driven rotary motor
- bacterial flagella motor
- FoF1-ATP synthase
with Glycerol phosphate shuttle you only get ___ atp
2 atp/2 e
why do you only get 2 atp with Glycerol phosphate shuttle
Doesn’t involve membrane transport since the mitochondrial glycerol-phosphate dehydrogenase is on the outside surface of the inner membrane.
just goes to complexes 2 and 3
Malate/aspartate shuttle gives ____ atp
3 atp/2e
Malate/aspartate shuttle (~3 ATP/2 e-) present in___
liver and heart
Glycerol phosphate shuttle (~2 ATP/2 e-), present in
some muscle and nerve cells.
adp/atp trnsslocator is ___
electrogenic
bc you are eliminating one of the positive charges
One P - and one H+ move in trnaslocator results in
a net loss of one H+ from the concentration gradient i
but with no change in charge (electroneutral).
what are the roles of H gradient?
