Cellular Respiration

AP Biology· difficulty 4/5

Isolated mitochondria consume O2 normally until cyanide is added.

Cyanide blocks Complex IV. Why does O2 consumption stop?

A
$Cyanide directly converts O2 to H2O$
B
$Cyanide replaces O2 in glycolysis$
C
$Cyanide breaks down ATP synthase, which is needed for O2 binding$
D
$O2 cannot accept electrons because Complex IV cannot transfer them, so the chain backs up$
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Explanation

Complex IV transfers electrons to O2. Blocking it halts electron flow through the entire chain, so NADH and FADH2 cannot be reoxidized and O2 use stops.

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