Question

Which one of the following statements about the events of noncyclic photophosphorylation is incorrect?

• A. Photolysis of water takes place
• B. $O_2$ is released
• C. Only one photosystem participates
• D. ATP and NADPH are produced

Answer 1

The correct option is C Only one photosystem participates

Photosystem II has P680 reaction center 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. Immediately after removal of four electrons from the two water molecules, O2 is released. Sunlight driven splitting of water is called as photolysis. Noncyclic photophosphorylation includes the flow of electron from PSII through quinone, cyt $b_6$ 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. Both PSI and PSII are involved; absence of PSII leads to cyclic photophosphorylation. Splitting of water and flow of electron through cytochrome $b_6$f complex add protons to thylakoid lumen. These protons are moved back to stroma through proton channels of ATP synthesis drives the synthesis of ATP. Thus, the correct answer is option C.