Question

Select the correct option:

The Z scheme of photophosphorylation follows the following sequence:

PS II$\underset{A}{\to }{e}^{-}acceptor\underset{B}{\to }ETS\underset{B}{\to }PSI\underset{C}{\to }{e}^{-}acceptor\underset{D}{\to }NAD{P}^{+}$
Which of the following option for A, B, C and D transfer of electrons?
A B C D

• A. A-Uphill; B-Downhill; C-Uphill; D-Downhill
• B. A-Downhill; B-Uphill; C-Downhill; D-Uphill
• C. A-Downhill; B-Uphill; C-Uphill; D-Downhill
• D. A-Uphill; B- Downhill; C-Downhill; D-Uphill

Answer 1

Answer: (A)

A-Uphill; B-Downhill; C-Uphill; D-Downhill

• A: The electron transfer from PS II to the electron acceptor is uphill.
• B: The electron transfer from the electron acceptor to the electron transport system (ETS) and from the ETS to the PSI are both downhill.
• C: The electron transfer from the PSI to the electron acceptor is uphill.
• D: The electron transfer from the electron acceptor to NADP+ is downhill.

So, the correct answer is 'A-Uphill; B-Downhill; C-Uphill; D-Downhill'.