Question

In the absence of $NAD{P}^{+}$, electrons of photosynthetic electron transport system pass to

• A. Cyt. f
• B. Cyt. $b_6$
• C. Plastocyanin
• D. Quinine

Answer 1

The correct option is B Cyt. $b_6$

In cyclic electron transport pathway:

1. The P${}_{700}$ pigment complex absorbs solar energy. They transfer their energy to PS I reaction centre- P${}_{700}$. The outer valance electron of excited P${}_{700}$ is raised to a higher energy level which is captured by the primary acceptor of PS I. The primary acceptor transfers electron to ferredoxin.

2. Reduced ferredoxin, unable to reduce NADP${}^{+}$ returns the electron to PS I via cytochrome b${}_6$, plastoquinone (PQ), cytochrome-f and plastocyanin.

3. The electron transport is called cyclic because the electron emitted from PS I returns back to PS I passing through several intermediate carriers.

Hence, the correct answer is 'Cyt.b6'.