Question

What is wrong with photorespiration?

Answer 1

Photorespiration:

1. Photorespiration is the process that involves the loss of fixed carbon as CO₂ in plants in presence of light.
2. It is also known as the C2 cycle. It is initiated in the chloroplasts, but it seems to occur in peroxisomes.
3. This process does not produce ATP or NADPH & is a wasteful process.
4. Photorespiration occurs usually when there is a high concentration of oxygen.
5. Under such circumstances, RuBisCO, the enzyme that catalyzes the carboxylation of RuBP during the first step of the Calvin cycle, functions as an oxygenase.
6. Some O₂ does not bind itself to RuBisCO and hence CO₂ fixation is decreased.
7. The RuBP binds with Oxygen to form one molecule of PGA (3C compound) and phosphoglycolate (2C compound) in the pathway of photorespiration.
8. Rather, it results in the release of CO₂ with the utilization of ATP.
9. It leads to a 25% loss of the fixed CO₂​. O₂ is first utilized in chloroplasts and then in peroxisomes.