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In sugarcane, 14CO2 is fixed into malic acid. The enzyme that fixes CO2 here is

  • (a) ribulose phosphate kinase Your answer
  • (b) phosphoenol pyruvate carboxylase Correct
  • (c) ribulose bisphosphate carboxylase Your answer
  • (d) fructose phosphatase Your answer
Your answer: Correct answer: (b)
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Explanation

Why (b) is correct

Sugarcane is a C4 plant. CO2 is first fixed in the mesophyll by PEP carboxylase, giving oxaloacetic acid, which becomes malic acid.

Why the other options are wrong

  • (a) · your answer Ribulose phosphate kinase regenerates RuBP; it does not fix CO2.
  • (c) · your answer RuBisCO fixes CO2 into PGA in the bundle sheath, not into malic acid.
  • (d) · your answer Fructose phosphatase is a sugar-processing enzyme, not a carboxylase.
NCERT point: In C4 plants, the mesophyll cells are rich in PEPcase but lack RuBisCO.
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