Question

The reaction which is responsible for the primary fixation of CO₂ is catalysed by

• A. PGA synthase
• B. RuBP carboxylase and PEP carboxylase
• C. PEP carboxylase
• D. RuBP carboxylase

Answer 1

The correct option is B

RuBP carboxylase and PEP carboxylase

RuBP carboxylase is responsible for the fixation of CO₂ in C₃ plants, while PEP carboxylase fixes CO₂ in C₄ plants. RuBP carboxylase uses ribulose-1, 5- bisphosphate as the CO₂ acceptor for the carboxylation reaction, while PEP carboxylase uses phosphoenol pyruvate as a CO₂ acceptor for carboxylation.

RuBisCO is the most abundant enzyme in the world and present in very high concentration in chloroplasts. It is required in very high concentration for