ETC & Ox Phos Flashcards
Only ~35% of the E released from the oxidation of NADH is captured by the synthesis of 2.5 ATP molecules. The rest of the free E is released as
heat
Summary of ETC & OxPhos:
- ETC: Electrons are stripped from NADH or FADH2 and passed along the electron transport chain until transferred to O2 –> H2O
- Meanwhile, H+ are pumped across the IM out of the matrix into the cytosol
- Ox Phos: H+ ions are allowed back into the matrix via ATP synthase
- The potential E of dissipating this ion gradient is captured to power the synthase –> ATP produced from ADP
Cytochromes types A, B, and C each have different ___.
Cytochrome electron carriers have ____ in their center, which is important because___
Each have different protoporphyrin ring structures
All have iron (Fe) which goes between the 2+ (reduced) and 3+ (oxidized) states to carry electrons
Iron-sulfur proteins
Fe is coordinated to the protein through cystein sulfur-containing side groups. Fe cycles between the +2 (reduced) and +3 (oxidized) states
Ubiquinone (coenzyme Q) carries ___ electrons, so it has 3 redox states: __, ___, and __.
carries 2 electrons
Ubiquinone (Q)
Semiquinone (QH)
Ubiquinol (QH2)
What is the order of the protein complexes of the ETC?
I - NADH dehdyrogenase
II - succinate dehydrogenase
III - ubiquinone cytochrome c oxidoreductase
IV - cytochrome oxidase
What happens at complex I
NADH dehydrogenase turns NADH to NAD+
4 H+ pumped out of matrix
Complex II of ETC
Succinate dehydrogenase- entry point for FADH2
FADH2 it produces from CAC is transferred into the ETC through iron/sulfur proteins
No H+ pumped
Complex III of ETC
Ubiquinone/CoQ is a lipid-linked carrier that receives e- from Complex I or II and transfers it to…
Complex III, which contains heme and iron/sulfur protein e- carriers.
4H+ are pumped out of the matrix
After complex III, electrons are transferred to ___ and then to ___, which has heme & copper to transfer these electrons to O2 to create H2o.
In the process, __ additional H+ ions are pumped out of the matrix
Complex III > Cyt C > Cytochrome oxidase > O2
2 additional H+ are pumped out of the matrix
Distingusih electron flow from NADH and FADH2
NADH skips Complex II : Complex I > CoQ …..
FADH2 skips Complex I : Complex II > CoQ…
Different electron sources that enter Co enzyme Q
NADH dehydrogenase (Complex I)
Succinate dehydrogenase (Complex II)
IMM G3P dehydrogenase (Glycerol-phosphate shuttle)
Acyl-CoA Dehydrogenase (FA-oxidation)
Electrons from NADH in complex I provide enough E to pump a total of _ H+ out of the matrix
Electrons from FADH2 in complex II provide enough E to pump a total of __H+ out of the matrix.
Generating a negative matrix and a positive intermembrane space.
NADH .. 10 H+
FADH2 .. 6 H+
Describe the ATP synthase complex
-
F0 is embedded in the membrane; its C10 ring forms a pore in the membrane that lets H+ enter the matrix.
- As H+ enters, they cause the ring to rotate in the lipid bilayer (electrochemical E is converted to mechanical E)
- F1 spins when the ring does, causing the B subunit to bind ADP Pi and then synthesize ATP when it strikes the F0 gamma subunit.
It takes ~ __ H+ to spin the F1 subunit sufficiently to generate ox phos of ADP to ATP
4 H+
Rotenone
broad-spectrum pesticide/insecticide that inhibits electron transfer between Complex I and CoQ
Everything downstream stays oxidized - no oxphos.
Antimycin A
Fish poison
blocks cytochrome C oxidoreductase
Cyanide or CO inhibit
cytochrome oxidase in complex IV
Poisons that inhibit either the ETC or ATP synthase caues
heart attack because without ATP, the heart doesn’t pump and the lungs don’t fxn
Aurovertin, Oligomycin, Venturicidin, and DCCD inhibit..
ATP synthase
Chemical uncouplers
Allows H+ to re-enter the matrix without ATP synthase
The E is released as heat instead of proton motive force (can cause hyperthermia)
DNP
An uncoupler.
In the acidic cytosol, it binds a proton that makes it neutral –> can penetrate IMM to enter matrix –> loses its proton, dissipating the proton gradient
FCCP
similar to dNP
Where does uncoupling occur naturally?
Brown fat in your shoulders and back have a bunch of cytochrome-containing mitochondria and expresses a natural uncoupler, thermogenin to generate heat.
Regulation of oxidative phosphorylation
- Stimulated by ADP
- Inhibited by ATP (& lowkey lactic and pyruvic acid)
- Requires oxygen
Ions and other polar molecules are transported across the inner membrane by
specific protein translocases that nearly balance charge during the transport process
How do ATP and ADP enter the inner mitochondrial membrane?Co
ATP-ADP antiporter (type of cotransporter)
Maintains charge across the membrane
Transporters that dissipate the overall positive H+ ion charge and the proton motive force:
- Pyruvate & H+ symporter into the matrix
- HPO42- & H+ symporter into the matrix
- Ca2+ enters the matrix
THIS IS ANOTHER REASON WHY ATP FROM ETC AND OXPHOS IS LESSENED (2.5 and 1.5 instead of 3 and 2)
Total net ATP yield from complete oxidation of glucose is
30 or 32, depending on the shuttle system used
All o the electron transfer reactions in the ETC result in the translocation of protons from the matrix to the inner membrane space EXCEPT the one catalyzed by
Complex II
What do we mean when we say that the processes of electorn transport and ATP synthesis are coupled?
If ATP synthesis does not occur, the H+ gradient becomes so steep that H+ cannot be translocated
CO binds specifically to cytochrome a in Complex IV and disrupts its ability to transfer electorns. IF high conc of carbon monoxide are added to actively respiring mitochondria,
- CoQ will become more oxidized, while cytochrome c will become more reduced
- CoQ will become more reduced, while cytochrome c will become more oxidized
- both CoQ and cytochrome c will become more reduced
- both will become oxidized
- both CoQ and cytochrome c will become more reduced
What will be the consequences of adding an uncoupler to actively respiring mitochondria?
Rate of electorn ransport will increase, but the extent of proton gradient and the rate of ATP synthesis will both decrease
