With reference to the properties of Photosystem I (PS I) and Photosystem II (PS II):
I. In PS I, the reaction centre Chlorophyll a absorbs maximally at 700 nm wavelength. II. In PS II, the reaction centre Chlorophyll a absorbs maximally at 680 nm wavelength. III. PS I is present in both grana thylakoids and stroma lamellae. IV. PS II is present in both grana thylakoids and stroma lamellae.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct. PS I (P700) occurs in both grana and stroma lamellae, whereas PS II (P680) is confined to grana thylakoids. Statement IV is incorrect.
Question 82 of 100
📘 CLASS XI
Consider the following statements regarding the Z-scheme of electron transport:
I. Electrons excited from PS II are picked up by an electron acceptor and passed to an electron transport system of cytochromes. II. The movement of electrons down the cytochrome chain is an uphill process on the redox potential scale. III. Electrons from the cytochrome chain are delivered to PS I. IV. Concurrent excitation of PS I leads to electron transfer to an acceptor that ultimately reduces NADP⁺ to NADPH + H⁺.
Which of the statement(s) given above is/are correct?
Statements I, III and IV are correct because electrons move from PS II to PS I through the cytochrome chain and finally reduce NADP⁺. Statement II is incorrect because electron flow is downhill on the redox potential scale.
Question 83 of 100
📘 CLASS XI
Regarding the mechanism and location of photolysis of water:
I. Water splitting is catalysed by an enzyme complex physically associated with PS II. II. Water splitting occurs on the stroma-facing surface of the thylakoid membrane. III. Photolysis generates electrons that continuously replace those lost by PS II. IV. The oxygen generated during photolysis is released into the thylakoid lumen.
Which of the statement(s) given above is/are correct?
Statements I, III and IV are correct because photolysis occurs on the lumen side of the thylakoid membrane, replenishes PS II electrons and releases oxygen into the lumen. Statement II is incorrect because the water-splitting complex is located on the lumen-facing side, not the stroma side.
Question 84 of 100
📘 CLASS XI
Consider the following statements regarding cyclic photophosphorylation:
I. Cyclic photophosphorylation involves only Photosystem I. II. It occurs in stroma lamellae due to the absence of PS II and NADP reductase. III. In cyclic flow, excited electrons return to PS I via the electron transport chain. IV. Cyclic photophosphorylation produces both ATP and NADPH + H⁺.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because cyclic electron flow operates only through PS I in stroma lamellae where PS II and NADP reductase are absent, causing electrons to cycle back to P700. Statement IV is incorrect because cyclic photophosphorylation synthesizes only ATP and not NADPH + H⁺.
Question 85 of 100
📘 CLASS XI
Regarding the development of the proton gradient during thylakoid electron transport:
I. Splitting of water molecules releases protons directly into the thylakoid lumen. II. Plastoquinone transfers protons from the stroma across the membrane into the lumen. III. The NADP reductase reaction consumes protons from the stroma side of the membrane. IV. These processes create a high proton concentration (low pH) in the stroma and a low proton concentration (high pH) in the lumen.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because photolysis releases protons into the lumen, plastoquinone transports protons from the stroma to the lumen, and NADP reductase consumes protons from the stroma. Statement IV is incorrect because the lumen has high proton concentration (low pH), while the stroma has low proton concentration (high pH).
Question 86 of 100
📘 CLASS XI
Consider the following statements regarding ATP Synthase (CF₀-CF₁ complex):
I. The CF₀ channel is embedded in the thylakoid membrane and facilitates proton diffusion across the membrane. II. The CF₁ headpiece is situated on the stroma-facing surface of the thylakoid membrane. III. Proton flow through CF₀ occurs from stroma to lumen against the electrochemical gradient. IV. Conformational change in the CF₁ particle drives the catalytic synthesis of ATP from ADP and inorganic phosphate.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because CF₀ forms the proton channel, CF₁ projects into the stroma, and proton flow induces conformational changes that synthesize ATP. Statement III is incorrect because protons move from the lumen to the stroma down their electrochemical gradient.
Question 87 of 100
📘 CLASS XI
Regarding the primary carbon fixation product in C₃ and C₄ photosynthetic pathways:
I. In C₃ plants, the first stable product of carbon fixation is 3-phosphoglyceric acid (3-PGA), a 3-carbon compound. II. In C₄ plants, the first stable product of carbon fixation is oxaloacetic acid (OAA), a 4-carbon compound. III. Melvin Calvin used radioactive ¹⁴C to identify 3-PGA in algal photosynthesis studies. IV. Both C₃ and C₄ plants use RuBP as their initial carbon dioxide acceptor in mesophyll cells.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because 3-PGA is the first stable product in C₃ plants, OAA is the first product in C₄ plants, and Calvin identified 3-PGA using ¹⁴C-labelled carbon dioxide. Statement IV is incorrect because C₄ plants initially use PEP, not RuBP, as the primary CO₂ acceptor in mesophyll cells.
Question 88 of 100
📘 CLASS XI
Consider the following statements regarding the primary CO₂ acceptor in C₃ plants (RuBP):
I. RuBP is a 5-carbon ketose sugar. II. Combination of one RuBP molecule with one CO₂ molecule produces two molecules of 3-PGA. III. The carboxylation reaction of RuBP is catalysed by RuBisCO. IV. RuBP is permanently consumed in carboxylation and cannot be regenerated inside the cell.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because RuBP is a 5-carbon ketose sugar that combines with CO₂ under the action of RuBisCO to yield two molecules of 3-PGA. Statement IV is incorrect because RuBP is regenerated during the regeneration phase of the Calvin cycle.
Question 89 of 100
📘 CLASS XI
Regarding the total input and output stoichiometry of the Calvin cycle for synthesis of one molecule of glucose:
I. Synthesis of one glucose molecule requires 6 turns of the Calvin cycle. II. Fixation of 6 CO₂ molecules requires an input of 18 ATP molecules. III. Fixation of 6 CO₂ molecules requires an input of 12 NADPH molecules. IV. The output of 6 turns of the Calvin cycle includes 1 molecule of glucose, 18 ADP, and 12 NADP⁺.
Which of the statement(s) given above is/are correct?
All four statements are correct. Six turns of the Calvin cycle fix six molecules of CO₂ to produce one glucose molecule while consuming 18 ATP and 12 NADPH, yielding glucose, ADP and NADP⁺ as products.
Question 90 of 100
📘 CLASS XI
Consider the following statements regarding Kranz anatomy in C₄ plants:
I. Bundle sheath cells form several tight layers around vascular bundles in C₄ leaves. II. Bundle sheath cells contain a large number of chloroplasts. III. Bundle sheath cell walls are thick and impervious to gaseous exchange. IV. Intercellular spaces are abundant between adjacent bundle sheath cells to allow rapid gas diffusion.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because Kranz anatomy consists of tightly packed bundle sheath cells with abundant chloroplasts and thick gas-impermeable walls. Statement IV is incorrect because bundle sheath cells lack intercellular spaces.
