Question

Steps in noncyclic photophosphorylation include passage of electrons along
(A) ${ FRS\rightarrow { FD\rightarrow { Cytb6 } } }\rightarrow { Cytf }\rightarrow { PC }\rightarrow { Chla }\\ $
(B) ${ Chla\rightarrow { Cytb6\rightarrow { Cytf } } }\rightarrow { PC }\rightarrow { PSI }{ \rightarrow FRS }\rightarrow { FD }\\ \\ $
(C) ${ Chla\rightarrow { PQ\rightarrow { Cytb6 } } }\rightarrow { Cytf }\rightarrow { PC }{ \rightarrow PS1 }\rightarrow { FRS\rightarrow }{ FD }\\ \\ \\ $
(D) ${ { PQ\rightarrow { Cytb6 } } }\rightarrow { Cytf }\rightarrow { PC }{ \rightarrow PS1 }\rightarrow { FRS\rightarrow }{ FD }\\ \\ \\ \\ \\ $

Answer 1

Hint: In non-cyclic photophosphorylation, the electrons which are released by ${ P 680 }$( photosystem II) after absorbing light are first accepted by the primary electron acceptor and finally reach the NADP at the end.

Complete answer:
In non-cyclic photophosphorylation, electrons are excited by PSII and then first accepted by the primary electron acceptor which transfers electrons to PQ.PQ transfer electrons to the cytochrome complex in which ${ Cyt b6 }$ is followed by Cyt f. Further electrons are passed to PC which transfers electrons to PSI and further helps in the excitation of electrons. Those excited electrons are again accepted by the primary electron acceptor and passed to FD.
In Non-cyclic photophosphorylation, when electrons are accepted by the primary electron acceptor, the chlorophyll molecules which are present in PSII are oxidized and an electron-hole is created which is to be filled. So, the electrons are extracted from water and passed to the PSII in order to fill the electron-hole. This splits water molecules into two hydrogen ions and one oxygen atom. This single oxygen atom combines with another oxygen atom to form ${ O }_{ 2 }$.
When at last the electron reaches $NAD{ P }^{ + }$ reductase, it results in the formation of NADPH. NADPH is further used in the production of glucose in the Calvin cycle.

So, the correct answer is ‘${ { PQ\rightarrow { Cytb6 } } }\rightarrow { Cytf }\rightarrow { PC }{ \rightarrow PS1 }\rightarrow { FRS\rightarrow }{ FD }\\ \\ \\ \\ \\ $’.


Note: Non-cyclic photophosphorylation is also known as a Z-scheme. The name Z- scheme was coined because the redox diagram represents the Z. The movement of electrons from different sites leads to the formation of the characteristic shape of the alphabet Z.