Consider the following statements regarding the proton gradient development in chloroplast chemiosmosis:
I. Water splitting on the inner side of the thylakoid membrane accumulates protons inside the lumen. II. Plastoquinone removes protons from the stroma while accepting electrons and releases them into the lumen side. III. The NADP reductase enzyme on the stroma side removes protons from the stroma to reduce NADP+. IV. These combined steps increase proton concentration in the stroma while decreasing proton concentration in the lumen.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because water splitting, plastoquinone activity and NADP reduction contribute to proton gradient formation. Statement IV is incorrect because proton concentration increases inside the lumen and decreases in the stroma.
Question 12 of 100
📘 CLASS XI
Regarding the ATP Synthase enzyme complex in thylakoids, evaluate the following statements:
I. ATP synthesis is driven by the breakdown of the proton gradient across the thylakoid membrane. II. The CF0 portion is embedded in the thylakoid membrane and forms a transmembrane channel. III. Protons cross the CF0 channel from stroma to lumen by active transport. IV. The CF1 headpiece protrudes into the stroma and undergoes conformational changes to synthesize ATP.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because ATP synthase utilizes proton diffusion from lumen to stroma through CF0, driving ATP synthesis by CF1. Statement III is incorrect because proton movement is passive and occurs from lumen to stroma.
Question 13 of 100
📘 CLASS XI
Consider the following statements regarding the biosynthetic phase (dark reaction) of photosynthesis:
I. The biosynthetic phase is directly light-driven and ceases immediately in dark conditions. II. It depends on the products of the light reaction (ATP and NADPH) along with CO2 and H2O. III. When light becomes unavailable, the biosynthetic phase continues for some time and then stops. IV. Calling the biosynthetic phase "dark reaction" is a misnomer because it does not require darkness to occur.
Which of the statement(s) given above is/are correct?
Statement I is incorrect because the biosynthetic phase is not directly dependent on light. Statements II, III and IV are correct because it depends on ATP and NADPH from light reactions and may continue briefly after light is removed.
Question 14 of 100
📘 CLASS XI
Regarding the primary CO2 acceptor and first stable product in the C3 pathway, evaluate these statements:
I. Melvin Calvin used radioactive 14C in algal photosynthesis to map the carbon assimilation pathway. II. The first stable product identified in C3 plants was 3-phosphoglyceric acid (3-PGA), a 3-carbon organic acid. III. Scientists initially searched for a 2-carbon acceptor compound expecting a 2+1=3 carbon addition. IV. The primary CO2 acceptor in C3 plants is Ribulose-1,5-bisphosphate (RuBP), a 5-carbon ketose sugar.
Which of the statement(s) given above is/are correct?
All four statements are correct. Calvin used radioactive carbon to trace carbon fixation, identified 3-PGA as the first stable product, scientists initially searched for a 2-carbon acceptor, and RuBP was later established as the 5-carbon primary CO2 acceptor.
Question 15 of 100
📘 CLASS XI
Consider the following statements regarding the three stages of the Calvin Cycle:
I. Carboxylation is the fixation of CO2 into RuBP, catalysed by RuBisCO, producing two molecules of 3-PGA. II. Carboxylation is catalysed by RuBP carboxylase-oxygenase because the enzyme possesses both carboxylation and oxygenation activities. III. Reduction requires 2 molecules of ATP for phosphorylation and 2 molecules of NADPH for reduction per CO2 molecule fixed. IV. Regeneration of one RuBP molecule requires 2 molecules of ATP and 1 molecule of NADPH.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because RuBisCO catalyses carboxylation and reduction requires ATP and NADPH. Statement IV is incorrect because RuBP regeneration requires ATP only and does not require NADPH.
Question 16 of 100
📘 CLASS XI
Regarding the overall stoichiometry and energetics of the Calvin cycle for the synthesis of one glucose molecule:
I. Six turns of the Calvin cycle are required for the formation of one molecule of glucose. II. The fixation of 6 CO2 molecules requires a total input of 18 ATP molecules. III. The fixation of 6 CO2 molecules requires a total input of 12 NADPH molecules. IV. The net output for 6 CO2, 18 ATP, and 12 NADPH entering the cycle is 1 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 are required to synthesize one glucose molecule, consuming 18 ATP and 12 NADPH. The overall products include one glucose along with 18 ADP and 12 NADP+.
Question 17 of 100
📘 CLASS XI
Consider the following statements regarding Kranz anatomy in C4 plants:
I. Large cells forming several layers around vascular bundles in C4 leaves are called bundle sheath cells. II. Bundle sheath cells are characterized by having a large number of chloroplasts and thick cell walls. III. Bundle sheath cells possess prominent intercellular spaces to facilitate gas exchange. IV. Maize and Sorghum are classic examples of plants exhibiting Kranz anatomy.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because Kranz anatomy includes chloroplast-rich bundle sheath cells with thick walls and is found in plants such as maize and sorghum. Statement III is incorrect because bundle sheath cells lack intercellular spaces.
Question 18 of 100
📘 CLASS XI
Regarding primary carbon dioxide fixation in C4 plants, consider the statements below:
I. The primary CO2 acceptor is Phosphoenolpyruvate (PEP), a 3-carbon molecule located in mesophyll cells. II. Fixation of CO2 in mesophyll cells is catalysed by PEP carboxylase (PEPcase). III. Mesophyll cells of C4 plants are rich in the enzyme RuBisCO. IV. The initial product of CO2 fixation in mesophyll cells is Oxaloacetic acid (OAA), a 4-carbon organic acid.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because PEP accepts CO2 through PEP carboxylase to produce OAA. Statement III is incorrect because mesophyll cells of C4 plants lack RuBisCO.
Question 19 of 100
📘 CLASS XI
Consider the following statements regarding the Hatch and Slack Pathway (C4 Cycle):
I. OAA formed in mesophyll cells is converted into malic acid or aspartic acid and transported to bundle sheath cells. II. In bundle sheath cells, 4-carbon acids are decarboxylated to release CO2 and a 3-carbon molecule. III. The released 3-carbon molecule is transported back to mesophyll cells where it is converted back to PEP. IV. Bundle sheath cells lack RuBisCO but contain high levels of PEPcase.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because C4 acids transport CO2 to bundle sheath cells and the resulting 3-carbon compound returns to mesophyll cells to regenerate PEP. Statement IV is incorrect because bundle sheath cells contain RuBisCO and lack PEP carboxylase.
Question 20 of 100
📘 CLASS XI
Regarding spatial division of photosynthetic pathways in C3 versus C4 plants:
I. In C3 plants, the Calvin cycle takes place in all photosynthetic mesophyll cells. II. In C4 plants, initial fixation occurs in mesophyll cells, while the Calvin cycle occurs exclusively in bundle sheath cells. III. C4 plants do not require the Calvin cycle because sugars are formed directly in the mesophyll. IV. The basic pathway resulting in sugar synthesis (Calvin cycle) is common to both C3 and C4 plants.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because the Calvin cycle is common to both C3 and C4 plants, occurring in mesophyll cells of C3 plants and bundle sheath cells of C4 plants. Statement III is incorrect because C4 plants also require the Calvin cycle.
