GATE 2023 ES – Question 39
Consider i Endogenous aerobic metabolism uses an electron acceptor inside cells;ii Its acceptor is DO;iii Endogenous metabolism is linked to fermentation;iv Exogenous aerobic metabolism has enzyme-mediated electron transfer inside cells. Choose the correct option.
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Correct answer: (A) i and iii correct
Explanation
The official key is **A**,using endogenous to describe internal donor/acceptor fermentation. This terminology conflicts with the common wastewater meaning of endogenous aerobic respiration, where stored/cellular material is oxidized and oxygen remains the terminal acceptor; under that usage ii is true and iii is not generally true. Enzymatic respiratory electron transfer also occurs within the cell/membrane system. The original statements and official answer are preserved, but the solution distinguishes the source’s fermentation-based use from standard endogenous aerobic decay.