Exam 2 Lecture 20 OxPhos Flashcards
What are the 2 membrane systems of the mitochondria
Outer and inner membrane
Why is the outer membrane permeable?
Presence of porin aka voltage dependent anion channel VDAC
Why is the inner membrane impermeable
Has metabolite transporters; very selective NADH and FADH2 are polar and use special transport
What are the 2 compartments of the mitochondria
Intermembrane space and matrix
Matrix of mitochondria is site of
TCA cycle and fatty acid oxidation
Ox Phos occurs where
In inner membrane
TCA cycle generates NADH and FADH2 which, in Ox Phos, flow through
4 protein complexes called the ETC
E-s reduce molecular O2 to
H20
Protons return to matrix by flowing through another complex called
ATP synthase
What is the mission of Ox Phos
- To transfer e-s from NADH and FADH2 to O2
- To establish proton gradient across the inner mito membrane
- To synthesize ATP
Electron flow is exergonic or endogonic?
Exergonic
Succinate Q reductase mechanism
Does not produce protons but moves protons from one complex to another
Succinate Q reductase has succinate dehydrogenase which
Generates FADH2 in TCA cycle
Complex I, III, and IV called
Respirasome
What are the 3 complexes that shuttle e-s from NADH to O2?
- NADH Q oxidoreducatase (complex I)
- Q cytochrome c oxidoreductase (complex III)
- Cyctochrome c oxidase (complex IV)
What are the 2 mobile e- carriers? Ie helpers?
- Coenzyme Q aka ubiquinone
2. Cytochrome c
Mechanism of coenzyme Q
Transfers e-s from NADH Q oxidoreductase and the Succinate Q reductase to Q cytochrome c oxidoreductase
E-s from complex I and II and transfers to complex III
What makes coenzyme Q hydrophobic
Long tail made of 5 - C isoprene units
Mechanism of cytochrome c
Shuttles e-s from Q cytochrome c oxidoreductase to cytochrome c oxidase
Ie shuttles e-s from complex complex III to complex IV
Cytochrome catalyzes _
Reduction of O2
What is the first point of entry of e-s from NADH
Complex I aka NADH dehydrogenase aka NADH-Q oxidoreductase
Complex I is encoded by both _ and _ genes
Nuclear and mitochondrial genes
Iron sulfur clusters undergo what reaction?
Redox; donates e-s
Do protons leave iron sulfur clusters present in iron sulfur proteins?
No
FADH2 enters the ETC through
Complex II aka succinate-Q reductase
Complex II connects _ to Oxphos (succinate dehydroenase)
TCA
Which complexes produce protons?
Complex I, III, and IV
Does FADH2 leave complex II?
No, donates e-s; e-s will be moving foward not FADH2
- e-s -> FeS -> Q to from QH2 *
What is occurring in Complex III?
E-s from QH2 (complex II) are passed on to cytochrome c via complex III.
Flow of e-s through complex III leads to transport of 2 protons to cytoplasmic side
What is happening in Complex IV, the final stage of the ETC cascade?
4 e-s are funned to O2 (final acceptor) to reduce it to H20. Concomitantly, protons are pumped from matrix to cytoplasmic side of inner membrane
What is the 1 job of Cytochrome c Oxidase and what is it made of (structurally)?
One job is to transfer e-s; made of 2 heme and 3 Cu
Free radical is a toxic derivative of _
Oxygen
How are reactive oxygen species (ROS) formed?
By partial reduction of O2
ROS include:
- superoxide ion
- peroxide ion
- hydroxyl radical
Mitochondria are a result of an _ event
An endosymbiotic event is thought to have occurred whereby a free-living organism capable of oxidative phosphorylation was engulfed by another cell.
Superoxide dismutase (SOD) functions to do what?
cellular defense strategy that scavenges superoxide radicals by catalyzing the conversion of two of these radicals into hydrogen peroxide and molecular oxygen
what is the function of catalse
takes the hydrogen peroxide formed from SOD and catalyzes the dismutation of hydrogen peroxide into water and molecular oxygen
Glutathione peroxidase functions to
cellular defense as it scavenges hydrogen peroxide
T/F: Vit E and C are other cellular defenses against oxidative damage
true. Vit E is lipophilic so is useful in protecting membranes from lipid peroxidation
Eukaryotes contain 2 forms of SOD, which are:
- Mn/Zn SOD present in mitochondria
- Cu/Zn SOD dependent cytoplasmic form
transfer of a _ e- to O2 forms superoxide ion, whereas the transfer of _ e- yields peroxide
transfer of 1 e- = superoxide and transfer of 2 e-s = peroxide
Glucose + 10NAD+ + 2FAD + 2(ADP + Pi) + 2 (GDP + Pi) ->
6CO2 + 10(NADH + H+) + 2FADH2 + 2ATP + 2GTP
THE OXIDATION OF FUELS (phase 1 of respiration)
10 NADH = 25 ATP (2.5 per H+) 2 FADH = 3 ATP (1.5 per H+) 2 GTP = 2 ATP 2 ATP = 2 ATP NET TOTAL = 32 ATP
