In C₃ plants, which enzyme first reacts with CO₂ to form PGA?

Correct option is B

• In C₃ plants, the first step of the Calvin cycle (C₃ cycle) involves the enzyme Ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco).

• Rubisco catalyzes the fixation of CO₂ to Ribulose-1,5-bisphosphate (RuBP), forming an unstable six-carbon compound.

• This compound immediately breaks down into two molecules of 3-Phosphoglycerate (PGA).

• PGA is then used in subsequent steps of the Calvin cycle to produce glucose and other organic molecules.

• C₃ plants include wheat, rice, and barley, where PGA (3-phosphoglycerate) is the first stable product of photosynthesis.

• Rubisco is the most abundant enzyme on Earth but has low efficiency because it can also react with O₂, leading to photorespiration.

  

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