Question

Which one is involved in the path of electron transport in case of both cyclic and non-cyclic photophosphorylation?

• A. Plastoquinone
• B. Cytochrome f
• C. P680
• D. Pheophytin

Hint:

Think about which carrier is shared between the electron transport chains of both PSI cyclic flow and PSII-PSI linear flow.

Answer 1

The Correct Option is A

Step 1: Non-cyclic photophosphorylation uses both Photosystem II and Photosystem I, moving electrons through pheophytin, plastoquinone, the cytochrome b6f complex containing cytochrome f, and finally to NADP+.

Step 2: Cyclic photophosphorylation involves only Photosystem I, where electrons from P700 pass through ferredoxin and back through the cytochrome b6f complex and plastoquinone, returning to P700 without ever reaching Photosystem II or NADP+.

Step 3: P680 and pheophytin belong specifically to Photosystem II and are not part of the cyclic pathway. Plastoquinone is the carrier common to the shared electron path in both cyclic and non-cyclic schemes as it shuttles electrons between the photosystem complex and the cytochrome b6f complex in both routes.