Lecture_No_5-Regulation_of_Respiration

Lecture_No_5-Regulation_of_Respiration - Respiratory...

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Respiratory control: Rate of oxidative phosphorylation is determined by the need for ATP 1. Electron transport and ATP synthesis is coupled. 2. Electrons do not flow through the electron-transport chain to O2 unless ADP is simultaneously phosphorylated to ATP. 3. When [ADP] rises, the rate of oxid. phos. increases to meet the ATP needs. (This is the case in active muscle) 4. The regulation of the rate of oxid. phos. by the ADP level is called Respiratory control or Acceptor control.
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Respiratory control: [ADP] affects the rate of TCA cycle In a resting muscle, [ADP] is low, NADH and FADH2 are not consumed by the ETC. Less NAD+ and FAD available, thus the TCA cycle slows. As [ADP] rises and oxid phos. speeds up, NADH and FADH2 are oxidized, leading to a more active TCA cycle.
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UCP-1, Brown Fat and uncoupling Some organisms have the ability to uncouple oxid. Phos. from ATP synthesis to generate heat. This is used to maintain body temp in hibernating animals or newborn animals. In response to a temp drop, the release of hormones leads to the liberation of free fatty acids from triacylglycerols that in turn activate UCP-1. UCP-1 (uncoupling protein 1) forms a pathway for the flow of H+ from the cytoplasm to the matrix. UCP-1 generates heat by short-circuiting the mitochondrial proton battery. The tissue with high UCP-1 called brown fat. (combination of greenish cytochromes and red hemoglobin in blood supply)
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Cyanide (CN - ), azide (N 3 - ) react with the ferric (Fe 3+ ) form of heme a3. Carbon monoxide (CO): Inhibits the ferrous (Fe 2+ ) form. Inhibits electron flow from Cyt b H Inhibits electron flow in Complex I Prevents the utilization of NADH as a substrate. Site of action of some inhibitors of electron transport
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Inhibition of ATP synthesis Oligomycin and DCCD (dicyclohexylcarbodiimide) Prevent the influx of protons through ATP sythase. In the presence of these drugs, the electron-transport chain ceases to operate. Thus, further confirming that electron transport and ATP synthesis are normally tightly coupled.
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The compound 2,4-dinitrophenol (DNP) acts as a proton ionophore, that is, it binds protons on one side of a membrane, and being fat-soluble it drifts to the opposite side where it loses the protons. In the presence of DNP, electron transport from NADH to O2 is normal, but no ATP synthesis, since the proton gradient is disrupted. This leads to further increased O2 consumptioin and NADH oxidation. Eventually, large amounts of metabolic fuels are consumed, but no energy is captured as ATP. Energy is releasd as heat. DNP is used as a weight-loss drug for some people. Soviet soldiers were given DNP to keep warm during the long Russian winters. Uncoupling electron transport form ATP synthesis
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This note was uploaded on 04/11/2011 for the course BCHM 562 taught by Professor Staff during the Winter '08 term at Purdue.

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Lecture_No_5-Regulation_of_Respiration - Respiratory...

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