Atractyloside, a plant toxin, is added to isolated respiring mitochondria supplied with abundant ADP, Pi, and substrate. Oxidative phosphorylation soon ceases even though all respiratory chain complexes remain intact. Atractyloside produces this effect by acting on:

• A Cytochrome c oxidase
• B ATP synthase stalk (F1)
• C The phosphate carrier protein
• D The adenine nucleotide translocase ✓

Explanation

Atractyloside binds the inner membrane adenine nucleotide translocase (ANT), locking it and preventing exchange of matrix ADP for cytosolic ATP. With no ADP delivered to the matrix, ATP synthase stalls, the proton gradient builds to its limit, and respiration falls by respiratory control, although the chain itself is intact. Oligomycin targets Fo, and cyanide targets complex IV, mechanisms different from this transport blockade.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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