Question

In the above schematic diagram, which is plastocyanin?

A)a
B)b
C)c
D)d

Answer 1

Hint: The schematic diagram represents the transfer of electrons through the photosystems involved in the photosynthesis. The Photosystems are the structural and functional protein complexes which altogether carry out the process of photosynthesis and produce energy.

Complete answer:
PSII- The photosystem II is a protein complex which is a multi- pigment complex. This complex receives electrons through the photolysis of water. The oxygen evolved combines to form molecular oxygen which is released into the atmosphere.
PSI- It is an integral membrane protein complex which utilises the light energy and transfers the electron across the membrane of the thylakoid from plastocyanin to ferredoxin. This electron transfer produces the energy carrier molecule called NADPH.

The electron transfers start from PSII and pass through primary electron acceptor ferredoxin (a) and then to plastoquinone (b) and then to cytochrome f. The electron moves to PS I through plastocyanin (d). This produces oxygen and NADPH.

Ferredoxin- It is an iron-sulphur protein complex which involves flow of electrons.
Plastoquinone- It is a quinone molecule which takes part in the electron transport chain of light reaction in photosynthesis.

Hence, the correct answer is option (D)

Note: Plastocyanin is a copper containing molecule which helps in transfer of electrons from PSII to PSI. It receives the electron from cytochrome f and transfers it to the PSI. The plastocyanin also helps in cyclic electron flow in the photosynthetic prokaryotes.