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Biochemistry

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Chemiosmotic Theory: Effect of Inhibitors

BIOCHM-R1EGPJ

Below is a generic drawing of a mitochondrial (mt) electron transport chain with the 4 electron transfer complexes (I-IV), associated proton pumping, and the ATP synthase shown relative to the inner membrane, as labeled.

Use your understanding of the Chemiosomotic theory and this drawing as a reference to determine which of the following statements accurately describes the coupling of electron transport with ATP synthesis as studied in isolated animal mitochondria.

M. Rumpho-Kennedy. Created for Albert.io. Copyright 2016. All rights reserved.

A

In the presence of the uncoupler dinotrophenol (DNP; see structure below), electron transfer and oxygen consumption will continue, but ATP synthesis will decrease. DNP is a lipophilic proton transporting ionophore that dissipates the proton gradient.

MantOs. DNP. Wikimedia Commons, 18 Jan. 2007. Web. 5 Feb. 2016.

B

In the presence of oligomycin, which physically blocks the ATP synthase proton channel, electron transfer and oxygen consumption will increase, but ATP synthesis will decrease.

C

In the presence of cyanide, an inhibitor of cytochrome oxidase, electron transfer from NADH or succinate will decrease. However, oxygen consumption will increase and heat will be generated.

D

In the presence of an inhibitor of electron flow from NADH to complex III, electron transfer and ATP synthesis will stop.