Photorespiration

Why photorespiration ?

Because Rubisco is not 100% specific for CO₂ ; Km for CO2 is 9 μM whereas for O2 is 350 μ M. In 3-4 turnovers , Rubisco catalyzes the condensation of O2 in place of CO2. As a result of this one C₃ ( 3-PG) and one C₂ ( 2- phosphoglycolate ) are formed.

Photorespiration	Normal respiration
1. Chloroplast + peroxisome + mitochondria	mitochondria
2. Gly immediate precursor	TCA intermediates
3. O2 utilized in the first step	O2 utilized in the last step
4. consumes ATP	Produces ATP
5. does not produce NADH	Produced NADH
6. Salvage pathway	Main pathway
7. No electron transfer	Electron transfer
8. Peroxide is produced	No peroxide formed