Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. Isolated chloroplast stroma is kept in darkness and supplied with carbon dioxide, ATP and NADPH. Organic compounds are formed for a limited period. This result shows that:

2. A graph plots photosynthetic carbon fixation on the vertical axis and incident light intensity on the horizontal axis. Near the origin, the graph is approximately a straight rising line. This region indicates that:

3. Two artificial photosystems contain identical reaction centres. System P has functional antenna pigments, while System Q has . Under weak light, each antenna pigment independently captures the same average amount of usable light. The expected ratio of captured excitation events in P and Q is:

4. Consider the following statements about the energy balance of carbon fixation.
I. The Calvin cycle requires ATP and NADPH in a ratio per carbon dioxide fixed.
II. Its ATP requirement is proportionally greater than its NADPH requirement.
III. Cyclic photophosphorylation directly produces additional NADPH.
IV. Cyclic electron flow can supplement ATP when non-cyclic flow supplies insufficient ATP relative to NADPH.
Which combination is valid?

5. Illuminated thylakoid preparations give the following results.

Which preparation most clearly demonstrates complete non-cyclic photophosphorylation?

6. Before transfer from mesophyll to bundle-sheath cells, OAA may be converted into another -carbon acid such as ______.

7. Consider the following statements about Priestley’s observations.
I. A candle and a mouse each altered the limited air of a closed enclosure.
II. A mint plant could restore the ability of enclosed air to support burning and animal survival.
III. The experiments established that plant-mediated restoration occurs only in sunlight.
IV. The experiments proved that evolved oxygen is derived from water.

8. Six external carbon-dioxide molecules are initially fixed by six PEP molecules in mesophyll cells. Each four-carbon product is later decarboxylated in bundle-sheath cells. Ignoring intermediate names not required here, which symbolic summary correctly represents the carbon flow?

9. A chloroplast fixes carbon-dioxide molecules through the Calvin cycle. Assuming complete pathway accounting, which outcome is consistent with the carbon and energy requirements?

10. A chloroplast contains stacked thylakoids, unstacked membranes connecting the stacks, and a fluid matrix surrounding the membrane system. The carbon-fixation enzymes are located mainly in the:

11. Four curves plot photosynthetic rate against light intensity for the same plant.
Curve P: suitable temperature and high carbon dioxide
Curve Q: suitable temperature and low carbon dioxide
Curve R: low temperature and high carbon dioxide
Curve S: low temperature and low carbon dioxide
All four curves nearly overlap at very low light. At high light, P has the highest plateau, S the lowest, and Q and R have intermediate plateaus. Which interpretation is best supported?

12. All chlorophyll a molecules are selectively removed from a photosynthetic membrane, while chlorophyll b, xanthophylls and carotenoids remain intact and continue absorbing light. Which outcome is most likely?

13. 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:

14. Arrange the carbohydrate-related events represented by Sachs’s interpretation in the most appropriate order.
P. Light acts on chlorophyll-containing green tissue.
Q. Glucose is formed through photosynthetic activity.
R. Part of the glucose is converted into stored starch.
S. Iodine reveals the accumulated starch.

15. Equal chloroplast preparations are supplied with carbon dioxide and suitable light-reaction products.

Which treatment most strongly indicates failure of the reduction phase?

16. A transported C4 acid enters a bundle-sheath cell, but its decarboxylation enzyme is inactive. Initial mesophyll fixation and acid transport continue briefly. The most immediate downstream consequence is:

17. Which paired symbolic directions correctly represent proton movement during gradient formation and gradient use?

18. Photosystem II remains illuminated and initially transfers electrons into the interphotosystem chain, but photosystem I cannot absorb usable light. Which pattern is expected during the early response?

19. A leaf that has been photosynthesising steadily is suddenly placed in darkness while carbon dioxide and temperature remain suitable. The most likely short-term sequence is:

20. An illuminated chloroplast treatment produces the following pattern: oxygen evolution remains near normal, NADPH formation is substantial, the lumen-to-stroma proton difference is very small, ATP formation is strongly reduced, PGA accumulates and RuBP regeneration declines. Which primary defect best explains the complete pattern?

21. Evaluate the following statements about wavelength and photosynthetic effectiveness.
I. Photosynthetic rate is generally high in blue and red light.
II. The green region is usually less effective than the major blue and red regions.
III. Photosynthesis must be exactly zero at every wavelength outside the major peaks.
IV. Accessory pigments can contribute to activity at wavelengths weakly absorbed by chlorophyll a.

22. A leaf-pigment chromatogram contains a blue-green chlorophyll band, a yellow-green chlorophyll band and a yellow-orange carotene band. The expected fourth principal pigment group, associated with a distinctly yellow band, is ______.

23. Two otherwise comparable preparations give the following results.

Which conclusion integrates all three observations?

24. Two identical plants receive red light of equal intensity. Plant P is illuminated for , while Plant Q is illuminated for . Temperature, water, carbon dioxide and dark-period respiration are otherwise comparable. If neither plant reaches another limitation during illumination, which prediction is most reasonable?

25. 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?

26. 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?

27. Use the pathway described below. Light excites , its electron enters an acceptor and carrier sequence, and the same electron returns to oxidised instead of reducing . This pathway is:

28. A transverse leaf section shows a vascular bundle surrounded by a continuous ring of large chloroplast-rich cells. Mesophyll cells form another layer outside this ring. This arrangement is identified as:

29. Stromal carbon reactions are receiving enough NADPH but require additional ATP to maintain their normal energy balance. Increasing which light-reaction route would meet this demand without supplying extra NADPH?

30. Arrange the events represented conceptually in van Niel’s photosynthetic relation.
P. The hydrogen donor loses reducing equivalents.
Q. Reducing equivalents become available for carbon reduction.
R. Carbon dioxide is reduced.
S. Generalised carbohydrate is formed.

31. Full sunlight at a site is light units, and photosynthesis of a particular leaf becomes light-saturated at approximately of full sunlight. An upper-canopy leaf receives units, while a lower-canopy leaf receives units. If light alone is changed, which prediction is most reasonable?

32. All light intensities in the following treatments lie within the linear low-light range, and contributions from different wavelengths are additive.

Treatment P supplies blue-light units and green-light units. Treatment Q supplies blue-light units and red-light units. Which prediction is correct?

33. A graph plots photosynthetic rate against external carbon-dioxide concentration for a well-watered leaf and a drought-stressed leaf. Both receive high light and suitable temperature. The well-watered curve rises strongly, while the drought-stressed curve remains low and responds only weakly to increasing external carbon dioxide. Stomata of the stressed leaf are mostly closed. Which explanation fits the graph?

34. Four proposed equations are shown below.

Which proposal is atom-balanced and consistent with water-derived oxygen evolution?

35. 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.

36. Consider the following statements about the net outcome of photorespiration.
I. Carbon dioxide is released.
II. ATP is consumed.
III. Sugar is produced as a net useful product.
IV. ATP and NADPH are generated.
Which combination is valid?

37. The overall green-plant relation is . If the process accounts for glucose molecules, which water and oxygen values are correct?

38. Match each investigator with the evidence most closely associated with the investigator’s contribution. A Column II entry is used once.

39. Photosystem II is experimentally inactivated, but photosystem I, suitable electron carriers, an intact thylakoid membrane and ATP synthase remain functional. Under illumination, which outcome is most plausible?

40. Match each product of photolysis with its principal immediate fate. A Column II entry is used once.

41. Compare two photosynthetic systems.

Which interpretation follows from the complete comparison?

42. Two chloroplast fractions produce the following results.

Which interpretation is correct?

43. Illuminated thylakoids are compared under the following conditions.

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

44. Which comparison correctly relates the major carboxylating enzymes in C3 and C4 plants?

45. A selective inhibitor blocks electron transfer from the photosystem-II acceptor system to the carriers that supply photosystem I. Both reaction centres can still absorb light, and water splitting remains initially functional. Which early pattern is expected?

46. Two treatments deliver the same total incident-light dose to identical leaves.

Which result follows from the data?

47. 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?

48. A mutation makes the walls of C4 bundle-sheath cells unusually permeable to gases while leaving PEP carboxylase and RuBisCO functional. The most likely consequence is:

49. Photosystem II is completely inhibited in an illuminated preparation, but photosystem I begins in a reduced state with an electron available at . A first flash produces a small amount of NADPH, whereas repeated flashes produce little additional NADPH and no oxygen. Which explanation is most appropriate?

50. Consider the following statements about interpreting photosynthetic response graphs.
I. A plateau after increasing light means that another factor may be limiting.
II. A decline at extremely high light can indicate photoinhibition rather than ordinary saturation.
III. One temperature optimum must apply universally to all plant species.
IV. External carbon-dioxide enrichment may produce little response when light remains very low.
Which combination is valid?