GATE 2020 BT Q.14: solution and answer

Official answer: BSource: Official answer key, GATE 2020 BT (IIT Delhi)

1. An energy-transducing membrane converts one form of energy into another. It carries an electron transport chain that pumps protons, and an ATP synthase (${\text{F}}_0{\text{F}}_1$) that uses the resulting proton-motive force to make ATP.

2. P, the bacterial plasma membrane, carries the respiratory electron transport chain and ${\text{F}}_0{\text{F}}_1$ ATP synthase. Bacteria have no mitochondria, so this membrane does the job. P is energy transducing.

3. Q, the inner membrane of the chloroplast (the inner envelope membrane), is a permeability barrier. It holds transporters but no photosystems, no electron transport chain and no ATP synthase. The photosystems and ATP synthase sit in the thylakoid membrane, which is a separate internal membrane system. Q is not energy transducing.

4. R, the inner mitochondrial membrane, carries complexes I to IV and ATP synthase. It couples the oxidation of $\text{NADH}$ to ATP synthesis. R is energy transducing.

5. Only P and R qualify, so the answer is option (B).