During photorespiration, the phosphoglycolate (PGO) produced by RuBP oxygenation is eventually converted to phosphoglycerate (PGA); 75% of the carbon in PGO is recovered. How many molecules of PGO are required to generate two molecules of PGA through this route

Explanation:

1. Photorespiration occurs in plants and it is a wasteful pathway, it competes with the Calvin cycle. It begins when rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO) catalyzes both CO2 and O2 fixation) acts on O₂ instead of CO₂.

2. Photorespiration is initiated by the oxygenase activity of rubisco, the same enzyme that is also responsible for CO2 fixation.

3. Phosphoglycolate formed by O₂ fixation is recycled to the Calvin cycle intermediate phosphoglycerate in the photorespiratory pathway.

4. During oxygen fixation,1 molecule of PGA and 1 molecule of 2-phosphoglycolate are formed. The 2-phosphoglycolate  is converted back to PGA in the photorespiratory cycle.