Consider the following statements regarding early experiments on photosynthesis:
I. Joseph Priestley discovered oxygen in 1774 and hypothesized that plants restore to the air whatever breathing animals and burning candles remove. II. Jan Ingenhousz showed that sunlight is essential to the plant process that purifies air. III. Ingenhousz used an aquatic plant to demonstrate that small bubbles were formed around green parts only in darkness. IV. Priestley's experiment demonstrated that a mint plant placed under a bell jar enabled a mouse to stay alive and a candle to continue burning.
Which of the statement(s) given above is/are correct?
Statement I is correct because Priestley discovered oxygen in 1774 and proposed that plants restore air spoiled by animals and burning candles. Statement II is correct because Ingenhousz proved that sunlight is essential for air purification by plants. Statement III is incorrect because oxygen bubbles were produced only in sunlight, not darkness. Statement IV is correct because the mint plant allowed the mouse to survive and the candle to burn.
Question 2 of 100
📘 CLASS XI
Consider the following statements regarding historical milestones in photosynthesis research:
I. Julius von Sachs provided evidence in 1854 that glucose is produced when plants grow and is usually stored as starch. II. Sachs demonstrated that chlorophyll is located in special bodies (later called chloroplasts) within plant cells. III. T.W. Engelmann used a prism to split light and illuminated a red alga placed in a suspension of anaerobic bacteria. IV. Engelmann described the first action spectrum of photosynthesis, which resembles the absorption spectra of chlorophyll a and b.
Which of the statement(s) given above is/are correct?
Statements I and II are correct because Sachs demonstrated glucose formation, starch storage, and chlorophyll localization. Statement III is incorrect because Engelmann used a green alga (Cladophora) with aerobic bacteria. Statement IV is correct because Engelmann obtained the first action spectrum of photosynthesis.
Question 3 of 100
📘 CLASS XI
Regarding Cornelius van Niel's contributions to understanding photosynthesis, evaluate the following statements:
I. Cornelius van Niel demonstrated that photosynthesis is essentially a light-dependent reaction where hydrogen from a suitable oxidisable compound reduces carbon dioxide. II. In purple and green sulphur bacteria, H2S acts as the hydrogen donor and O2 is evolved as the oxidation product. III. Van Niel inferred that the oxygen evolved by green plants originates from H2O and not from carbon dioxide. IV. The origin of evolved oxygen from water was later conclusively proven using radioisotopic techniques.
Which of the statement(s) given above is/are correct?
Statement I is correct because Van Niel proposed the general equation of photosynthesis. Statement II is incorrect because sulphur bacteria produce sulphur or sulphate instead of oxygen. Statements III and IV are correct because oxygen in photosynthesis originates from water and this was confirmed using radioisotopes.
Question 4 of 100
📘 CLASS XI
Consider the following statements regarding chloroplast structure and internal division of labour:
I. Within the chloroplast, the membranous system consists of grana, stroma lamellae, and matrix stroma. II. The membrane system is responsible for trapping light energy and synthesizing ATP and NADPH. III. Enzymatic synthesis of sugars leading to starch formation takes place in the stroma matrix. IV. Starch granules and lipid droplets are located inside the thylakoid lumen.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct. The membrane system performs light reactions, while sugar synthesis occurs in the stroma. Statement IV is incorrect because starch grains and lipid droplets occur in the stroma, not the thylakoid lumen.
Question 5 of 100
📘 CLASS XI
With reference to photosynthetic pigments and chromatographic separation, consider the statements below:
I. Chromatographic separation reveals that leaf colour is due to four pigments: Chlorophyll a, Chlorophyll b, Xanthophylls, and Carotenoids. II. On a chromatogram, Chlorophyll a appears bright or blue-green, while Chlorophyll b appears yellow-green. III. Xanthophylls appear yellow, whereas carotenoids range from yellow to yellow-orange. IV. Chlorophyll a shows maximum light absorption exclusively in the green region of the visible spectrum.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct. Statement IV is incorrect because chlorophyll a absorbs mainly blue and red wavelengths while reflecting green light.
Question 6 of 100
📘 CLASS XI
Consider the following statements regarding accessory pigments in photosynthesis:
I. Chlorophyll b, xanthophylls, and carotenoids are categorized as accessory pigments. II. Accessory pigments transfer absorbed light energy directly to NADP+. III. Accessory pigments enable a broader range of incident light wavelengths to be utilized for photosynthesis. IV. Accessory pigments protect Chlorophyll a from photo-oxidation.
Which of the statement(s) given above is/are correct?
Statements I, III and IV are correct because accessory pigments broaden the absorption spectrum and protect chlorophyll a. Statement II is incorrect because they transfer energy to chlorophyll a rather than directly to NADP+.
Question 7 of 100
📘 CLASS XI
Regarding photosystems and light-harvesting complexes (LHC), evaluate the following statements:
I. Photosystem I (PS I) and Photosystem II (PS II) are named according to the functional sequence in which they operate during the light reaction. II. Each photosystem contains hundreds of pigment molecules bound to proteins, forming an antenna system. III. In PS I, the reaction centre Chlorophyll a has an absorption peak at 700 nm (P700). IV. In PS II, the reaction centre Chlorophyll a has an absorption peak at 680 nm (P680).
Which of the statement(s) given above is/are correct?
Statement I is incorrect because PS I and PS II were named according to their order of discovery rather than functional sequence. Statements II, III and IV are correct because photosystems possess antenna pigments and reaction centres P700 and P680 respectively.
Question 8 of 100
📘 CLASS XI
Consider the following statements concerning non-cyclic photophosphorylation and the Z-scheme:
I. Light absorption at 680 nm by PS II excites electrons that are transferred downhill along an electron transport chain of cytochromes on a redox potential scale. II. Electrons lost from PS II are permanently consumed in the cytochromes and never reach PS I. III. Excitation of PS I by 700 nm light transfers electrons to an acceptor with greater redox potential, ultimately reducing NADP+ to NADPH + H+. IV. Non-cyclic photophosphorylation results in the synthesis of both ATP and NADPH + H+.
Which of the statement(s) given above is/are correct?
Statements I, III and IV are correct because electron flow from PS II through cytochromes to PS I and finally to NADP+ constitutes the Z-scheme, producing both ATP and NADPH. Statement II is incorrect because electrons are transferred from PS II to PS I through the electron transport chain.
Question 9 of 100
📘 CLASS XI
Regarding the splitting of water (photolysis) during light reaction, consider the statements below:
I. The water-splitting complex is physically associated with PS II and located on the inner side (lumen side) of the thylakoid membrane. II. Splitting of water provides a continuous supply of electrons to replace those removed from PS II. III. Photolysis yields protons (H+), oxygen (O2), and electrons. IV. The oxygen and protons produced during photolysis are directly released into the stroma.
Which of the statement(s) given above is/are correct?
Statements I, II and III are correct because photolysis occurs on the lumen side of PS II and supplies electrons, protons and oxygen. Statement IV is incorrect because protons and oxygen are released into the thylakoid lumen, not the stroma.
Question 10 of 100
📘 CLASS XI
Consider the following statements regarding cyclic photophosphorylation:
I. Cyclic photophosphorylation occurs when only PS I is functional and excited electrons are cycled back to PS I through an electron transport system. II. Stroma lamellae membranes lack PS II as well as the NADP reductase enzyme. III. Cyclic photophosphorylation leads to the synthesis of both ATP and NADPH + H+. IV. Cyclic electron flow takes place predominantly when light of wavelengths beyond 680 nm is available.
Which of the statement(s) given above is/are correct?
Statements I, II and IV are correct because cyclic photophosphorylation involves only PS I and synthesizes ATP under conditions favouring cyclic flow. Statement III is incorrect because cyclic photophosphorylation does not produce NADPH.
