Question

In non-cyclic electron transport system, the path of electron is

• A. $PS-I\to PS-II\to NADP$
• B. $PS-II\to PS-I\to NADP$
• C. $NADP\to PS-II\to PS-I$
• D. $NADP\to PS-I\to PS-II$

Answer 1

The correct option is B $PS-II\to PS-I\to NADP$

• Photosystem II has P${}_{680}$ reaction centre wherein oxygen atoms of two water molecules bind to a cluster of manganese atoms.
• These Mn atoms are associated with an enzyme that splits water, removes electrons one at a time.
• After the removal of four electrons from the two water molecules, O${}_2$ is released. Sunlight-driven splitting of water is called as photolysis.
• Noncyclic photophosphorylation includes the flow of electron from PSII through quinone, cytochrome b6-f complex and plastocyanin to NADPH via PSI.
• NADP reductase enzyme is located on the stromal side of PSI and catalyzes the reduction of NADP into NADPH.
• Splitting of water and flow of electron through cytochrome b6-f complex add protons to thylakoid lumen.
• These protons are transported which drives the synthesis of ATP.

Thus, the correct answer is option B.