Let me share with you a difference between photorespiration and Calvin cycle.
| Aspect | Photorespiration | Calvin Cycle |
| Introduction | Photorespiration is a wasteful pathway that competes with the Calvin cycle. | Calvin cycle is an essential metabolic pathway for carbon fixation. |
| Takes place in | · Chloroplasts · Peroxisomes · Mitochondria | Chloroplasts |
| Initiation | First step of photorespiration is the oxygenation of ribulose-1,5-bisphosphate by Rubisco. | First step of Calvin cycle is carboxylation of RuBP by Rubisco. |
| Role in carbon fixation | No role in fixation of carbon dioxide and CO2 is released | Net fixation of carbon dioxide to form organic compounds. |
| Products | · No direct production of glucose or other useful organic molecules. · Produces no ATP | · Glucose · ATP · NADP+ |
| Energy consumption | Consumes ATP | Consumes ATP and NADPH |
| CO2 uptake or release | Uptake O2 and release of CO2 | Uptake CO2 and release O2 |
| Effect on photosynthesis | Reduction in the efficiency of photosynthesis. | Essential for the synthesis of organic compounds. |
| Occurrence | Common in C3 plants, particularly under high temperatures and high light conditions | Occurs in all photosynthetic plants |