Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. Arrange the events by which an accessory pigment contributes to photosynthetic electron excitation.
P. An accessory pigment absorbs a photon.
Q. Excitation energy moves through the antenna pigments.
R. Reaction-centre chlorophyll a becomes excited.
S. A high-energy electron is transferred to a primary acceptor.

2. Van Niel’s general relation may be written as:

If a photosynthetic organism uses as the hydrogen donor while fixing carbon-dioxide molecules, which symbolic outcome follows?

3. Cell fractions from a normal C4 leaf are accidentally mixed before enzyme analysis. Both PEP carboxylase and RuBisCO are then detected in the mixed sample. Why is the result insufficient to conclude that both enzymes normally function in the same cell?

4. A green plant is supplied with and carbon dioxide containing ordinary oxygen. The oxygen gas released during photosynthesis is enriched in . The strongest inference is that:

5. A graph plots proton concentration against time for the lumen and stroma of illuminated thylakoids. After light is switched on, Curve P rises while Curve Q falls. When light is switched off, the curves gradually move toward one another as ATP formation briefly continues. The curves represent:

6. Chloroplasts are treated so that all thylakoid membranes are destroyed, while stromal enzymes remain functional. The preparation is placed in darkness and supplied with carbon dioxide, RuBP, ATP and NADPH. Which outcome is most likely during the initial incubation?

7. A C3 crop and a C4 crop are exposed to a gradual rise from to under strong light and adequate water. Atmospheric carbon dioxide remains unchanged. Which change is most likely?

8. A C4 plant carries out normal PEP carboxylation, four-carbon-acid transport and bundle-sheath decarboxylation. An inhibitor selectively blocks ATP-dependent regeneration of RuBP in bundle-sheath chloroplasts. Which response is expected after the initial RuBP pool is consumed?

9. A compound makes the thylakoid membrane freely permeable to protons but does not initially inhibit pigment excitation or electron transfer. Soon after treatment, oxygen evolution and electron movement are still detectable, yet ATP production falls sharply. This pattern is best explained by:

10. Which statement best represents how external factors affect photosynthesis under natural conditions?

11. Arrange the events of Calvin-cycle carboxylation.
P. An unstable -carbon state is formed.
Q. Carbon dioxide combines with RuBP through RuBisCO.
R. Two molecules of PGA appear.
S. RuBP is available as the -carbon acceptor.

12. A mutation leaves all photosynthetic pigments chemically intact and preserves their normal wavelength absorption, but prevents reaction-centre chlorophyll a from transferring its excited electron to the primary acceptor. Which spectral result is expected?

13. A chloroplast has abundant ATP, normal RuBisCO activity and sufficient carbon dioxide, but NADPH formation has stopped. PGA continues to appear briefly but accumulates while triose-phosphate production falls. The best explanation is:

14. Four C4 leaf treatments are compared under high light and high temperature.

Which treatment most specifically indicates defective carbon-dioxide retention by unusually gas-permeable bundle-sheath walls?

15. A specific inhibitor completely blocks the channel without damaging electron carriers or the catalytic head. During illumination, the most likely pattern is:

16. Consider the following plant structures.
I. A mature green leaf
II. A chlorophyll-containing young stem
III. A colourless underground root
IV. A green sepal exposed to light
Which structures can reasonably contribute directly to photosynthesis under suitable conditions?

17. Mesophyll cells are exposed either to low light or to intense light for the same duration. Microscopy shows different chloroplast arrangements along their walls, while chloroplast number remains unchanged. The observations most strongly support the inference that chloroplast movement:

18. An intact thylakoid has lumen pH and stroma pH , while electron transport is absent. ADP and inorganic phosphate supplied only to the lumen produce no ATP, but supplying them to the stromal side produces a brief ATP pulse. Which inference is best supported?

19. Assertion: The term dark reaction is misleading when interpreted to mean that carbon fixation requires darkness.
Reason: Carbon reactions are not directly driven by photons, but they depend on ATP and NADPH normally produced in light.

20. An illuminated aquatic green plant releases bubbles that are collected in an inverted tube. The collected gas supports the renewed glowing of a splint. The most justified inference is that:

21. Under high light and abundant carbon dioxide, a photosynthetic-rate curve reaches a low plateau at . When temperature is raised to , the plateau shifts upward. Which factor was most directly limiting the original plateau?

22. Illuminated thylakoids are compared under the following conditions.

Which treatment contains the complete immediate requirements for strong chemiosmotic ATP formation?

23. Photosynthetic rate is measured at increasing light intensities.

Which conclusion best fits the complete dataset?

24. Illuminated thylakoids are subjected to the following treatments.

Which comparison most directly isolates the importance of membrane integrity while keeping electron transport and ATP synthase functional?

25. Non-cyclic electron flow must supply NADPH molecules. Assume each NADPH requires electrons and all electrons originate from photolysis according to . How many water molecules are split and oxygen molecules released?

26. Three regions of a chloroplast are described below.

Which interpretation correctly classifies the regions?

27. Which of the following is an internal factor that can influence the photosynthetic rate of a whole plant?

28. A learner rewrites as and then treats one unit of light as a molecule consumed in the reaction. The main error is that:

29. Two thylakoid systems begin with relative proton units in the lumen and in the stroma. Before any proton return through ATP synthase, photolysis adds units to the lumen and carrier action transfers units from stroma to lumen. In System P, NADP reduction additionally consumes stromal proton units; in System Q, NADP reduction is blocked. Which comparison is correct?

30. Organism P uses water during light-driven carbon fixation and evolves oxygen. Organism Q uses hydrogen sulphide, deposits sulphur and does not evolve oxygen. Their relationship is best described as:

31. A plant is supplied with while its carbon dioxide and initially stored carbohydrates remain unlabelled. Which observation is consistent with both isotope evidence and the expanded photosynthetic equation?

32. In a sulphur bacterium that normally uses during photosynthesis, the supply of is removed while light and carbon dioxide remain available. The most immediate expected effect is:

33. Twelve RuBP molecules react with RuBisCO under two gaseous conditions. In Condition P, undergo carboxylation and undergo oxygenation. In Condition Q, undergo carboxylation and undergo oxygenation. Which change from P to Q is correct?

34. Arrange the following consequences of developing water stress in a leaf.
P. Internal carbon-dioxide availability declines.
Q. Soil-water shortage develops.
R. Stomata close.
S. Carbon fixation decreases.

35. Consider the following statements about suppression of photorespiration in C4 plants.
I. Carbon dioxide is released from four-carbon acids in bundle-sheath cells.
II. The released carbon dioxide raises its concentration near RuBisCO.
III. High local carbon dioxide favours the carboxylase activity of RuBisCO.
IV. The mechanism requires phosphoglycolate to accumulate around RuBisCO.
Which combination is valid?

36. Mesophyll and bundle-sheath cells from a C4 leaf are homogenised together without destroying PEP carboxylase or RuBisCO. Initial PEP fixation and Calvin-cycle reactions can still be detected, but photorespiration rises compared with the intact leaf. Which explanation is most appropriate?

37. Intact thylakoids are first placed in an acidic medium so that their lumen becomes proton-rich. They are then rapidly transferred in darkness to an alkaline medium containing . ATP is formed briefly even though no light-driven electron transport is occurring. The result shows that:

38. An unknown plant displays the following characteristics: a -carbon primary acceptor, a -carbon first stable product, coordinated mesophyll and bundle-sheath reactions, negligible photorespiration and a high temperature optimum. Which single classification fits all observations?

39. A plant receives and unlabelled . Which symbolic outcome is consistent with the established source of photosynthetic oxygen?

40. Compare the two RuBisCO reactions.

Which conclusion follows from the comparison?

41. Fixation of carbon-dioxide molecules requires ATP and NADPH. Non-cyclic electron flow supplies exactly ATP and NADPH. How much additional ATP must cyclic photophosphorylation provide?

42. A filamentous aquatic plant has alternating green and colourless regions. Under uniform illumination, bubbles appear mainly beside the green regions. This spatial pattern provides the strongest support for the idea that:

43. Assertion: Mesophyll cells form the major cellular site of photosynthesis in a typical green leaf.
Reason: Mesophyll cells usually contain numerous chloroplasts positioned within the internal photosynthetic tissue of the leaf.

44. Two C3 chloroplast preparations receive identical light-reaction supplies of ATP and NADPH and initially show equal RuBisCO carboxylation. Preparation P is exposed to conditions causing extensive photorespiration, while Q experiences little oxygenation. Even when carbon dioxide is replenished continuously, P shows lower sustained Calvin-cycle turnover. Which explanation is most appropriate?

45. A leaf retains normal chlorophyll-b absorption, but its action spectrum becomes selectively depressed in wavelength regions where chlorophyll b previously made a major contribution. The red action peak associated strongly with chlorophyll a remains nearly normal. Which defect best explains the result?

46. The results of four isotope treatments are summarised below.

Which pair provides the most direct comparison for identifying the molecular source of oxygen released during photosynthesis?

47. Assertion: ATP-dependent regeneration of RuBP is essential for sustained operation of the Calvin cycle.
Reason: Without regenerated RuBP, the pathway loses the -carbon acceptor required for additional carbon-dioxide fixation.

48. Two leaves have equal area and receive identical environmental conditions. Leaf P has well-developed mesophyll with many chloroplasts, while Leaf Q has poorly developed mesophyll with fewer chloroplasts. Which prediction is most justified?

49. A mature leaf increases its photosynthetic rate from to units after moderate carbon-dioxide enrichment. A senescent leaf from the same plant rises only from to units under the same treatment and has low chlorophyll and RuBisCO content. Which conclusion is best supported?

50. Examine the proposed Calvin-cycle relations.

Which proposal is internally consistent?