Mitochondrial Shuttles and ETC Flashcards
give a summary of the electron transport
- Complex I (NADH dehydrogenase) and Complex II (succinate dehydrogenase) can donate electrons to the lipid-mobile electron carrier Coenzyme Q (found within the inner-mitochondrial membrane)
- CoQ can donate electrons to Complex III (cytochrome reductase)
- Complex III can donate electrons to the mobile protein cytochrome C (foud within the inner-membrane space)
- cytochrome C will donate electrons to complex IV (cytochrome oxidase)
- complex IV will donate electrons to oxygen
name the prosthetic groups of each complex
- Compex I: FMN (riboflavin derivative)
- Complex II: FAD (riboflavin derivative)
- Complex III: heme groups (Fe3+)
- Complex IV: Cu2+ and heme groups (Fe3+)
where did the NADH electrons come from?
- NADH oxidized by CoQ at complex I
- pyruvate dehydrogenase
- isocitrate dehydrogenase
- a-KG dehydrogenase
- malate dehydrogenase
where did the FADH electrons come from?
- FADH electrons came from succinate dehydrogenase activity
- FADH oxidized by CoQ at Complex II
describe the oxidative phosphorylation and the chemiosmotic gradient
- as electrons flow down the electrochemical potential, protons are pumped into the intramembrane space
- protons are pumped into intramembrane space at complexes I, III and IV
- this creates a pH gradient that is relieved by pumping protons back through complex V
- the energy released in this process is coupled to ATP synthesis from ADP + P
describe the function of rotenone, piericidin A (antibiotic) and the barbituate amytal
- inhibit NADH dehydrogenase in complex I
describe the function of antimycin A (antibiotic)
- inhibits cytochrome b of cytochrome reductase (complex III)
describe the function of CO, azide, hydrogen sulfide (H2S) and cyanide (CN-)
- inhibit cytochrome oxidase (complex IV)
describe the function of oligomycin (antibiotic)
- inhibits ATP synthase
describe the transport of ATP and ADP
- adenine nucleotide translocase (ANT): unidirectional exchange of ATP for ADP (antiport)
- symport of Pi and H+ is electroneutral
name inhibitors of ANT
-
atractyloside: toxic glycoside from plant
- binds the outward facing (inter-membrane space) portion of the adenosine nucleotide transporter
-
bongkrekic acid: respiratory toxin produced in coconuts
- binds the inward facing (matrix) portion of the ANT
describe uncouplers of oxidative phosphorylation
- certain uncouplers (dinitrophenol, DNP), ASA (aspirin), thermogenin, ionophores act by destroying the proton gradient
- uncouplers decrease ATP synthesis and increase ETC and O2 consumption
describe thermogenin (aka UCP1)
- uncoupling protein
- found exclusively in brown adipocytes in mammals
- found in newborns in neck and upper back
- the H+ gradient generated from electron transport is uncoupled from ATP synthesis and generates heat
- this is the physiological function of brown adipose tissue
describe ionophores
- compounds that make the inner-membrane permeable to compounds that cannot usually cross
- both uncouplers and ionophores allow for dissipation of the proton gradient
name examples of ionophores
- gramicidin is a channel forming ionophore
-
valinomycin is a mobile carrier
- associated with carrying K+ across bilayers
describe the 2 shuttle mechanisms
- cells needs a mechanism to shuttle electrons from NADH (from glycolysis in the cytosol) across inner mt membrane
- 2 shuttle mechanisms:
- glycerophosphate shuttle results in the synthesis of 2 ATPs per cytosolic NADH oxidized (lower because NADH -> FADH)
- malate-aspartate shuttle results in the synthesis of 3 ATPs per cytosolic NADH oxidized (higher bc NADH stays as NADH)
describe the malate-aspartate shuttle
describe the glycerophosphate shuttle
