Let me share with you a difference between cyclic and non-cyclic phosphorylation.
| Aspect | Cyclic Photophosphorylation | Non-Cyclic Photophosphorylation or Z-Scheme |
| Electron pathway | Electrons follow a circular or cyclic pathway, returning to the same chlorophyll molecule | Electrons follow a linear pathway, moving from water to NADP+ |
| Destination of electrons | Electrons return to Photosystem I | Electrons move between both Photosystem II and Photosystem I |
| Production of ATP | ATP is produced during cyclic electron flow | ATP is produced during both Photosystem II and Photosystem I electron transport |
| Production of NADPH | No NADPH is produced | NADPH is produced in non-cyclic photophosphorylation |
| Oxygen evolution | Lower or absent in cyclic | Oxygen is evolved as a byproduct of water splitting in Photosystem II |
| Role in carbon fixation | Does not directly contribute to carbon fixation | Provides NADPH that are crucial for the reduction of carbon dioxide during the Calvin Cycle |
| Energy source | Uses light energy absorbed by Photosystem I chlorophyll | Utilizes light energy absorbed by both Photosystem II and Photosystem I chlorophylls |
| Occur in | · Common in certain bacteria · Some photosynthetic algae |
· Plants
· Algae · Cyanobacteria |