Question

Dark reaction of photosynthesis is

• A. Hill reaction
• B. Calvin cycle
• C. Cyclic photophosphorylation
• D. Non-cyclic photophosphorylation

Answer 1

Answer: (B)

Calvin cycle

Dark reaction of photosynthesis is Calvin cycle. Calvin cycle may be supported by $C_4$ cycle or Crassulacean Acid Metabolism (CAM) in certain plants. Calvin cycle was discovered by Melvin Calvin. The first stable product in Calvin cycle is 3-phosphoglyceric acid (PGA), hence it is also known as $C_3$ pathway. The primary acceptor molecule during $C_3$ cycle is a five-carbon ketose sugar- Ribulose bisphosphate (RuBP). The enzyme for $C{O}_2$ fixation is RuBIsCO (Ribulose Bisphosphate Carboxylase Oxygenase). It is the most abundant enzyme on earth. Calvin cycle occurs in three stages- Carboxylation, Reduction, and Regeneration.