Question

In photorespiration, which is a light induced cyclic oxidation of photosynthetic intermediates with the help of oxygen, the substrate is:

• A. Glycolate
• B. Glucose
• C. Pyruvic acid
• D. Acetyl Co-A

Answer 1

The correct option is A Glycolate

In the presence of high concentration of $O_2$, the enzyme RuBP oxygenase splits the molecule of Ribulose-1, 5 bisphosphate into one molecule of 3-phosphoglycerate and one molecule of 2-phosphoglycerate. The 2-phosphoglycerate undergoes dephosphorylation (loss of a phosphate group) and forms glycolate, hence it is also called the glycolate pathway. This process interferes in the activity of RuBisCo enzymes in binding of ${\mathrm{CO}}_2$. The lack of ${\mathrm{CO}}_2$ fixation inhibits photosynthesis and ATP production.