Question

How does photorespiration lower the efficiency of photosynthesis?

Answer 1

Photorespiration:

1. The Calvin cycle's first stage, carbon fixation by (RuBP Ribulose bisphosphate carboxylase-oxygenase) to create 3PGA (3-phosphoglycerate), is catalysed by the enzyme RuBisCO.
2. RuBisCO is attracted to both CO₂ and O₂. Some RuBisCO binds to O₂ in C₃ plants, which reduces carbon fixation.
3. When RuBP binds to O₂ in the photorespiration pathway, it creates phosphoglycerate and phosphoglycolate.
4. It makes use of ATP (Adenosine triphosphate) and emits CO₂. There is no ATP, NADPH, or sugar synthesis.
5. C₄ plants contain a mechanism that raises CO₂ concentration at the enzyme site, reducing photorespiration and increasing production.