Simulation · Biology · Class 11
RuBisCO's choice
From the lesson Photorespiration in Photosynthesis in Higher Plants. Change the values and watch what happens.
RuBisCO's choiceBiology · Class 11
The idea behind it
NCERT §11.9
- RuBisCO can bind both CO₂ and O₂ at its active site, and the binding is competitive: whichever gas is relatively more concentrated tends to bind. RuBisCO has a much greater affinity for CO₂ when CO₂ and O₂ are present in similar amounts.
- In C₃ plants some O₂ does bind RuBisCO. RuBP then combines with O₂ to give one molecule of phosphoglycerate and one of phosphoglycolate; this oxygenase route is photorespiration.
- Photorespiration makes no sugar and no ATP or NADPH. Instead it uses ATP and releases CO₂, making it a wasteful process.
- In C₄ plants photorespiration does not occur, because the mechanism concentrates CO₂ at the enzyme site in bundle sheath cells, so RuBisCO acts as a carboxylase and its oxygenase role is minimised.
- Lacking photorespiration helps explain why C₄ plants give better productivity and yields. They also tolerate higher temperatures. The biological function of photorespiration is still not known.