Cellular Respiration

AP Biology· difficulty 4/5

DNP, a small lipid-soluble acid, was added to mitochondria. O2 consumption rose sharply but ATP production fell.

What best explains DNP's effect?

A
$DNP inhibits O2 binding at Complex IV$
B
$DNP blocks ATP synthase but not the ETC$
C
$DNP increases NAD+ recycling in glycolysis only$
D
$DNP carries H+ across the inner membrane, dissipating the proton gradient and uncoupling ETC from ATP synthesis$
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Explanation

Uncouplers like DNP transport H+ across the membrane independently of ATP synthase. The gradient collapses, ETC runs faster (more O2 used) but no ATP is made; energy is lost as heat.

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