Electron Transport Chain Flashcards
ETC Outline
Final common pathway for electron carriers. Electrons pass down through protein carriers, releasing energy to form ATP from ADP and Phosphate (excess used in thermogenesis and Ca2+ transport).
where does glycolysis take place
Cell cytosol
Where does TCA cycle take place
Mitochondrial matrix (except for succinct dehydrogenase in membrane)
Transport of Molecules between cytosol and matrix
Substrate shuttles (transport proteins). Only carries electrons from cytosolic NADH (rebinds to NAD+ in matrix)
Glycerol-3-phosphate Shuttle Outline
Transfer of electrons from cytosolic NADH to matrix FAD
Malate-Aspirin Shuttle Outline
Transfer of electrons from cytosol NADH to matrix NAD+
Complex 1 Outline
NADH - Ubiquinoine oxireductase. Transfers electrons and proton from NADH to CoQ. Site of proton NADH pumping
Complex 2 Outline
Succinate Dehydrogenase. FAHH2 Transfers electrons from succinate to Co Q. Site of proton FADH2 pumping
Complex 3 Outline
Transfers electrons from Co Q and Cytochrome C
Complex 4 Outline
Electron transfer from cytochrome C to Oxygen
Number of NADH pumps
- Produce 3 ATP
Number of FADH2 pumps
- Produce 2 ATP
What gives electron carriers good affinity for electrons
Iron, Iron-sulfur and copper molecules attached. Fe3+ reduced to Fe2+ and reoxidised
Purpose of H+ conc gradient across mitochondrial matrix and membrane
Energy created from H+ moving down conc gradient through complex 5 produces ATP
Chemiosmotic Hypothesis Outline
Protons pumped (via 3 complexes of ETC) from membrane to inter membrane space (inner membrane is impermeable so H+ is trapped). The proton gradient is used to form ATP
ETC Complex 5 (F0 Unit) Outline
Integral membrane protein, H+ channel. Attached to ATP synthase (F1 unit). H+ moving through F0 causes confirmational change (rotation) resulting in F1 forming ATP out of ADP + P
Result of protein uncoupling in ETC
Transporters breakdown, H+ gradient isn’t formed. ATP isn’t formed, heat is formed instead (protein: thermogenin, found in brown fat)
Synthetic Uncouplers Outline
Drugs that increase the permeability of the inner-mitochondrial membrane (preventing H+ gradient forming). No ATP synthesis, heat synthesised (presents as fever). Eg aspirin overdose
Endogenous Uncouplers Outline
Compounds that increase permeability of inner mitochondrial membrane eg excess bilirubin (kernicterus) , uncouples electron oxidative-phosphorylation
Mitochondrial/OXPHOS Diseases
Defects in oxidative phosphorylation in ETC proteins due to mutations in mtDNA or nuclear DNA. Eg Parkison’s, Alzhimer’s
Heteroplasmy Def
Some DNA is mutated
Leber Hereditary Optic Neuropathy
Heteroplasmy, point mutations of mitochondrial components of ETC. Results in sudden onset blindness in young adults as optic nerve has high energy demand and oxidative phosphorylation is impaired
Result of any 1 complex in ETC being inhibited
ATP inhibition and cell death
Causes of complex inhibition
Iron deficency, riboflavin deficeny (complexes 1 and 2), cyanide (complex 4) and carbon monoxide (complex 4)
NAD Coenzyme
Niacin (B3)
FAD Coenzyme
Flavin (B2)
