Question:- Which of the following statements about photosynthesis are FALSE?  a) Photosystem II has a higher redox potential than water.  b) Plastocyanin donates its electrons to photosystem I.  c) Chloroplast ATP synthase releases ATP into the thylakoid space d) Water-splitting enzyme releases four protons into the thylakoid space for every water molecule that is split. e)cytochrome b6-f complex pumps protons into the thylakoid space.
Question:-
Which of the following statements about photosynthesis are FALSE?
 a) Photosystem II has a higher redox potential than water.
 b) Plastocyanin donates its electrons to photosystem I.
 c) Chloroplast ATP synthase releases ATP into the thylakoid spaceÂÂ
d) Water-splitting enzyme releases four protons into the thylakoid space for every water molecule that is split.ÂÂ
e)cytochrome b6-f complex pumps protons into the thylakoid space.
The Correct Answer and Explanation is:
Correct Answer: c) Chloroplast ATP synthase releases ATP into the thylakoid space
Photosynthesis is a complex process that occurs in the chloroplasts of plant cells, primarily involving the light-dependent reactions within the thylakoid membranes. Let’s examine each statement:
a) Photosystem II has a higher redox potential than water – FALSE
This statement is true, not false. Photosystem II (PSII) must have a lower (more positive) redox potential than water in order to oxidize it. In redox chemistry, a molecule with a higher redox potential accepts electrons more readily. Thus, PSII can extract electrons from water because it has a higher (more positive) redox potential than water.
b) Plastocyanin donates its electrons to photosystem I – TRUE
This is a true statement. Plastocyanin is a copper-containing electron carrier that transfers electrons from the cytochrome b6-f complex to Photosystem I (PSI) during the light reactions.
c) Chloroplast ATP synthase releases ATP into the thylakoid space – FALSE
This is the false statement and thus the correct answer to the question. Chloroplast ATP synthase synthesizes ATP on the stromal side of the thylakoid membrane, not into the thylakoid space. Protons accumulate in the thylakoid lumen, and the resulting proton gradient drives the production of ATP in the stroma where it is used for the Calvin cycle.
d) Water-splitting enzyme releases four protons into the thylakoid space for every water molecule split – TRUE
This is correct. The oxygen-evolving complex (part of PSII) splits two water molecules into O₂, four protons, and four electrons, releasing the protons into the thylakoid lumen.
e) Cytochrome b6-f complex pumps protons into the thylakoid space – TRUE
This statement is also true. The cytochrome b6-f complex is part of the electron transport chain and helps maintain the proton gradient by actively pumping protons into the thylakoid lumen.
Therefore, the FALSE statement is option (c).
