Cellular Respiration and Oxidative Phosphorylation Flashcards
The Steps of Cellular Respiration (and location)
- Glycolysis: glucose -> pyruvate; occurs in cytosol
- Pyruvate Dehydrogenase Complex: pyruvate -> acetyl CoA; occurs in mitochondria
- TCA Cycle: acetyl CoA -> CO2; occurs in mitochondria
- —- energy captured as NADH or FADH2 —- - Oxidative Phosphorylation: coupling of electron transport to ATP synthesis; occurs in mitochondria
- ETC: OXIDATIVE step; electrons captured as NADH and FADH2 in the preceding pathways are used to reduce oxygen to water
- ATP Synthesis: PHOSPHORYLATION step; energy captured in ETC is used to ADP -> ATP
Reduced form
H
FADH2 transfers e- directly to
CoQ; misses first H+ transfer step, no pumping H+=less energy made per FADH2
Oxidative Phosphorylation results in
O2->H2O
1ATP = __ H+?
3H+ = 1 ATP
ETC and ATP Synthesis is
COUPLED! a decrease in one results in an decrease in all
H+ gradient is referred to as
proton-motive force
Prerequisites for Oxidative Phosphorylation
- reduced forms of NADH and FADH2
- O2
- low ATP (high ADP)
- sufficient quantity of mitochondria
If the ETC were deficient, what would happen?
Pyruvate levels would decrease, and lactate levels would increase
Anaerobic Glycolysis
in cytoplasm; net yield of 2 mol ATP
2 ways to interfere with OxPhos
Inhibitors of the Respiratory Chain
-bind to one of the complexes in the ETC and stop oxidation-reduction reactions and electron transfer
Uncouplers
- break link between the rate of ET and synthesis of ATP
Atractyloside
- binds and inhibits ATP/ADP antiporter, preventing transport and availability of ADP in matrix for ATP synthesis
- in turn slows down ETC
Inhibitors that Disrupt Respiratory Chain
- Rotenone
- Antimycin
- CO
- Cyanide
- Oligiomycin
- Rotenone: (I)
- Antimycin: (III)
- CO: (IV)
- Cyanide: (IV)
- Oligiomycin: V
Rotenone
- potent inhibitor of NADH dehydrogenase (Complex I) of ETC
-
** WILL NOT COMPLETELY INHIBIT ETC ** No NADH will be able to be used, however FADH2 will still be able to be used as it enters at Complex II
^ significantly decreases proton gradient and amount of ATP produced
Antimycin
- inhibitor of Complex III
- electron carriers before III become fully reduced, and after III are completely oxidized
Cyanide (CN) Poisoning
- inhibitor of Complex IV; binds tightly to ferric iron Fe3+ state of cyt a3 (IV)
- NO NET ATP PRODUCTION: a3 gives e- to O2
- CN Antidote: Nitrite followed by thosulfate treatment (converts ferrous to ferric and allows for transport to hemoglobin rather than having in ETC)
CN distinct odor
bitter almonds
Carbon Monoxide
- inhibits Complex IV
Oligomycin
- binds to F0 portion of ATP synthase
- prevents transport of protons
- no ATP can be made
Uncouplers
molecules that allow protons to reenter the mitochondrial matrix from the intermembrane space INDEPENDENT of the proton-channeling function of ATP synthase
- allow ETC to proceed but ATP synthesis does not occur because no proton gradient established
- energy linked with the transport of electrons is dissipated as heat
- ** OXYGEN CONSUMPTION CONTINUES but NOT ATP IS PRODUCED **
2,4-dinitrophenol (DNP)
- Uncoupler
- Starves cells of ATP
(like high dose asprin)
Thermogenesis: Heat Production and Maintenance
- Shivering: uses ATP and generates heat
- Non-shivering Thermogenesis: use uncoupling to generate heat
- Thermogenin found in brown fat generates heat and maintains body temp (found in babies and bears)
Cyanide poison result
O2 will not be consumed, and no ATP will be generated
Oligomycin poison
O2 will not be consumed and no ATP will be produced
- blocking ATP synthase also inhibits the consumption of O2
DNP posion
DNP = uncoupler ( H+ “smuggler”)
- O2 will be consumed by no ATP will be produced
Malate-Aspartate Shuttle
transports cytoplasmic NADH into mitochondrial matrix in order to participate in OxPhos
- ** COMPLEX I ** 1 NADH = 3 ATP **
- NADH cytosol -> mitochondria
- reversible
- no ATP loss (Malate -> OAA conversion “pumps” NADH in)
- only works if [NADH]/[NAD+] is higher in cytoplasm than in matrix
- operates in liver, heart, and kidneys
Glycerol Phosphate Shuttle
transports cytoplasmic NADH into mitochondrial matrix in order to participate in OxPhos
- ** COMPLEX 3 ** BYPASS RXN ** 1NADH = 2 ATP ***
- irreversible
- NADH -> FADH2 exchange (NADH cytosol -> FADH2 mitochondria)
- yields 1 less ATP
- operates in brain and skeletal muscle: where you need energy fast!
- Faster than malate-aspartate
