Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. Match each type of evidence with the conclusion it most directly supports. A Column II entry is used once.

2. A membrane complex contains many chlorophyll and carotenoid molecules bound to proteins around one specialised chlorophyll a molecule. A primary electron acceptor lies next to the specialised pigment. This arrangement is best identified as:

3. A C4 plant and a C3 plant are exposed to increasing temperatures while light, water and carbon dioxide remain adequate. The C4 plant maintains a high photosynthetic rate at temperatures that substantially reduce the C3 rate. The most relevant explanation is:

4. Assertion: At high light intensity, the photosynthetic rate may approach a plateau even when illumination is increased further.
Reason: Once light is adequate, another factor such as carbon-dioxide availability or temperature-dependent enzyme capacity may become limiting.

5. Three comparable regions of a destarched leaf are tested under illumination. Region P is enclosed in a sealed chamber containing fresh KOH and remains starch-negative. Region Q is enclosed in a sealed chamber containing water and becomes starch-positive. Region R is placed with KOH in a loosely sealed chamber; after the experiment, the KOH is found exhausted and R becomes starch-positive. Which interpretation best explains Region R?

6. Photosynthetic rate is measured at increasing light intensities.

Which conclusion best fits the complete dataset?

7. Two illuminated green plants are treated as follows. Plant P receives with unlabelled carbon dioxide and releases labelled oxygen. Plant Q receives unlabelled water with and releases unlabelled oxygen. A claim that carbon dioxide is the source of evolved oxygen is:

8. Isolated thylakoids are illuminated under four treatments.

Which treatment most specifically demonstrates that electron acceptance must follow reaction-centre excitation?

9. A chloroplast has normal excitation of both photosystems and an intact interphotosystem carrier chain, but is unavailable. The most direct consequence for non-cyclic flow is:

10. Arrange the steps used to identify an early stable product of carbon fixation with a radioactive-carbon pulse.
P. Separate the cellular compounds.
Q. Expose photosynthesising cells briefly to .
R. Detect which separated compounds contain radioactivity.
S. Stop metabolism rapidly at defined times.
T. Compare early and later labelling patterns.

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

12. A graph plots wavelength from to on the horizontal axis and the proportion of incident light absorbed by a purified pigment on the vertical axis. It has prominent peaks in blue and red regions and a trough in the green region. The graph is a:

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

14. Equal leaf areas of a C3 plant and a C4 plant are grown under high light and high temperature. Their results are shown below.

Which interpretation is most appropriate?

15. Four proposed equations are shown below.

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

16. Two plants show the following daily carbon fluxes under warm, bright conditions.

Which comparison of net carbon gain is correct?

17. Illuminated thylakoids are analysed after four treatments.

Which treatment most specifically indicates inhibition of NADP reductase?

18. Photosystem II is inhibited in four chloroplast preparations. Which treatment would most directly test whether ATP from cyclic electron flow can support Calvin-cycle reduction when NADPH is supplied separately?

19. A tropical C3 species has a measured optimum near the upper end of the usual C3 range, while a cool-climate C4 species has an optimum near the lower end of the usual C4 range. Their values lie close to one another. Which conclusion is most appropriate?

20. 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:

21. Consider the following statements about light as an external factor in photosynthesis.
I. Light quality refers to the wavelength or colour composition of incident light.
II. Light intensity refers to the amount of light reaching a surface per unit time.
III. Duration refers to the length of time for which a photosynthetic surface remains illuminated.
IV. Increasing any one of these dimensions always increases photosynthesis without limit.
Which combination is valid?

22. Equal-sized, destarched leaf regions are maintained under the conditions shown.

After adequate treatment, the region most likely to become blue-black with iodine is:

23. Plasmodesmatal connections between C4 mesophyll and bundle-sheath cells are selectively sealed, while PEP carboxylase, decarboxylating enzymes, RuBisCO and the Calvin cycle remain functional within their original cells. Which pattern is expected?

24. 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?

25. Organism P fixes , uses water as its hydrogen donor and releases oxygen. Organism Q also fixes , but uses hydrogen sulphide and releases sulphur. Which conclusion best follows?

26. After leaving the primary acceptor of photosystem II, an electron normally:

27. A drought-stressed leaf is placed in air containing moderately elevated carbon dioxide, but its stomata remain tightly closed. Why may photosynthesis still show little improvement?

28. Evaluate the following statements about chloroplast positioning in mesophyll cells.
I. Chloroplasts can alter their arrangement in response to incident light.
II. Their movement occurs along the cell walls within the peripheral cytoplasm.
III. One fixed arrangement is optimal under every light condition.
IV. Position changes can help cells obtain a favourable quantity of light.

29. 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:

30. 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?

31. Match each component of Engelmann’s experiment with its role. A Column II entry is used once.

32. An intact leaf initially shows an action spectrum with major blue and red peaks and a moderate shoulder in an intermediate wavelength region. Its chlorophyll-a absorption spectrum is low in that intermediate region. After selective destruction of most accessory pigments, the shoulder nearly disappears and prolonged intense illumination causes a faster decline in photosynthesis. Which inference integrates both changes?

33. On a carbon-dioxide response graph obtained under high light, curve P reaches a plateau near , whereas curve Q continues rising beyond before approaching saturation. Which identification and interpretation are most appropriate?

34. 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?

35. Two inhibitors produce the following observations in illuminated thylakoids.

Which pairing of defects best explains P and Q?

36. Arrange the electron pathway represented by the Z scheme.
P. Primary acceptor of photosystem II
Q. Reaction centre of photosystem I
R.
S. Reaction centre of photosystem II
T. Intermediate electron carriers
U. Primary acceptor of photosystem I

37. A green plant that has been restoring altered air in sunlight is transferred to complete darkness while temperature and gas access remain unchanged. What is the most likely outcome after its available photosynthetic energy intermediates decline?

38. Assertion: Every organism that uses light energy to synthesise organic matter releases oxygen.
Reason: The product formed by oxidation of the hydrogen donor depends on the donor’s chemical identity.

39. 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:

40. Assertion: RuBP is the primary carbon-dioxide acceptor of the Calvin cycle, whereas PGA is its first stable product.
Reason: PGA is a -carbon compound produced after a transient -carbon state divides.

41. Consider the following statements about the autotrophic role of green plants.
I. They can synthesise organic compounds from inorganic raw materials.
II. They convert captured light energy into chemical energy.
III. They obtain all required organic food directly from other organisms.
IV. They can photosynthesise without carbon dioxide or water.

42. 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:

43. Photosynthetic rates are measured under four treatments.

Which comparison most directly isolates the effect of temperature?

44. Most antenna pigments are removed from a photosystem, but its reaction-centre chlorophyll a and primary electron acceptor remain functional. Which response is most likely?

45. Consider the following statements about the ecological association of C4 plants.
I. They are commonly found in dry tropical regions.
II. Strong light and relatively high temperature often favour their performance.
III. Every plant growing in a dry habitat necessarily uses the C4 pathway.
IV. Habitat alone is insufficient to prove the photosynthetic pathway of an unknown plant.
Which combination is valid?

46. The following table gives four proposed interpretations of the empirical photosynthetic relation.

Which proposal gives the biologically appropriate mapping?

47. The balanced overall equation for green-plant photosynthesis contains water and oxygen on opposite sides. Why is this equation alone insufficient to prove that evolved oxygen originates from water?

48. Compare the two photosynthetic plants described below.

Which identification is correct?

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

50. A graph plots photosynthetic rate against light intensity for the same plant at and . The curves nearly overlap at very low light. At high light, the curve reaches a much higher plateau. Which interpretation is best supported?