Light reaction, photosystems and photophosphorylation — practice questions

Question 1 · difficulty L1 · recall

What is the reaction-centre chlorophyll of Photosystem II called?

• A. P700, the reaction centre of Photosystem I
• B. P600
• C. P680
• D. P450

Question 2 · difficulty L2 · understanding

What is the immediate purpose of photolysis of water during the light reaction?

• A. To regenerate PEP in C4 plants
• B. To supply carbon dioxide for the Calvin cycle
• C. To produce glucose directly
• D. Replacement electrons for Photosystem II

Question 3 · difficulty L2 · understanding

How does cyclic photophosphorylation differ from non-cyclic photophosphorylation?

• A. Photosystem I only; ATP but no NADPH or oxygen
• B. It involves only Photosystem II and produces NADPH
• C. It produces oxygen but no ATP
• D. It requires both photosystems and splits water

Question 4 · difficulty L3 · understanding

Which out of the following statements is incorrect?

• A. Grana lamellae have both PS I and PS II
• B. Cyclic photophosphorylation involves both PS I and PS II
• C. Both ATP and NADPH + H$$^+$$ are synthesised during non-cyclic photophosphorylation.
• D. Stroma lamellae lack PS II and NADP reductase

Question 5 · difficulty L3 · understanding

The reaction centre in PS II has an absorption maxima at

• A. 700 nm
• B. 660 nm
• C. 780 nm
• D. 680 nm

Question 6 · difficulty L3 · application

A chloroplast preparation is illuminated, but Photosystem II is selectively blocked while Photosystem I remains functional. Which process could still occur?

• A. Non-cyclic electron flow from water to NADP+
• B. Cyclic photophosphorylation
• C. Photolysis of water coupled to oxygen evolution
• D. Normal production of both ATP and NADPH through linear flow

Question 7 · difficulty L3 · understanding

In light reaction, plastoquinone facilitates the transfer of electrons from

• A. PS-I to ATP synthase
• B. Cytb 6 f complex to PS-I
• C. PS-I to NADP +
• D. PS-II to Cytb 6 f complex

Question 8 · difficulty L4 · analysis

During non-cyclic electron flow, an electron originating from water eventually reduces NADP+. Which sequence best represents its path?

• A. NADP+ → Photosystem II → water → Photosystem I
• B. Water → Photosystem I → Photosystem II → NADP+
• C. H2O → PSII → carriers → PSI → NADP+
• D. Water → Calvin cycle → Photosystem I → NADP+

Question 9 · difficulty L5 · analysis

A thylakoid membrane can transport electrons normally, but it cannot maintain a proton concentration difference between its lumen and stroma. Which light-reaction product would be most directly reduced despite continued electron transfer?

• A. Reduction of electron carriers at the start of the chain
• B. Light absorption by pigments
• C. Excitation of reaction-centre chlorophyll
• D. ATP formation by chemiosmosis