Question
NEET 2022 (paraphrased): Regarding the detailed mechanism of photosynthesis, which of the following statements is correct? (a) photolysis refers to only ATP, no NADPH, only PS I (b) cyclic photophosphorylation is characterised by 2H₂O → 4H⁺ + 4e⁻ + O₂ at PS II (c) C₄ pathway — PEP carboxylase fixes CO₂ first, reduces photorespiration (d) quantum yield has no role in the detailed mechanism of photosynthesis
Solution — Step by Step
This option swaps the definitions. photolysis is actually 2H₂O → 4H⁺ + 4e⁻ + O₂ at PS II, not what (a) claims. So (a) is out.
Similarly, cyclic photophosphorylation means only ATP, no NADPH, only PS I. Option (b) is mismatched. Out.
This one reads correctly: C₄ pathway — PEP carboxylase fixes CO₂ first, reduces photorespiration. Match with NCERT wording confirms it.
quantum yield — ~8 photons per O₂ molecule released — plays a real role in the detailed mechanism of photosynthesis, so option (d) is factually wrong.
Correct answer: (c) C₄ pathway — PEP carboxylase fixes CO₂ first, reduces photorespiration.
Why This Works
NEET PYQs on the detailed mechanism of photosynthesis rely on definition swapping. The examiner takes two correct facts and pairs them with the wrong terms. If you know each fact cold, the MCQ dissolves in 20 seconds.
Alternative Method
For definition-swap MCQs, don’t read all four options first. Read option (a), decide true/false, then (b), and so on. This prevents confusion between similar-looking options.
NEET reuses the same fact set every 2–3 years with different distractors. Master the four NCERT facts on the detailed mechanism of photosynthesis listed here and you’ll handle almost any MCQ on this chapter.
Common Mistake
Students second-guess themselves when they see a familiar option listed as “wrong” in the stem. Trust the elimination — if you know the definition, stick with it.
Keep a one-page sheet of definitions for every NEET chapter. Revise only that sheet in the last 48 hours before the exam.