Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. The midpoint of the stated C3 optimum range is compared with the midpoint of the stated C4 range . What is the difference between the two midpoints?

2. Two chloroplast fractions are tested under the conditions shown.

The most appropriate identification is:

3. 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:

4. Examine the proposed carbon relations.

Which proposal correctly describes initial carbon fixation?

5. 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:

6. A destarched variegated leaf is exposed to light. After the iodine test, only its green regions become blue-black, while the non-green regions remain yellow-brown. The strongest conclusion is:

7. Transport of four-carbon acids from mesophyll to bundle-sheath cells is strongly reduced despite normal amounts of PEP carboxylase and RuBisCO in a C4 plant. Which effect most directly weakens its carbon-concentrating mechanism?

8. 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:

9. Assertion: Tropical plants commonly have higher photosynthetic temperature optima than plants adapted to temperate climates.
Reason: The temperature optimum of photosynthesis reflects adaptation of the plant’s enzymes and cellular processes to its usual habitat.

10. 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?

11. Photosynthetic rate is measured at increasing light intensities.

Which conclusion best fits the complete dataset?

12. In an experiment testing the need for carbon dioxide in starch formation, potassium hydroxide is placed inside a sealed container mainly to:

13. In a grassland, prolonged failure of photosynthesis sharply reduces new organic-matter production by grasses. The most defensible ecosystem-level prediction is:

14. 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?

15. 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.

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

Which proposal gives the biologically appropriate mapping?

17. 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?

18. Priestley’s bell-jar observations, Ingenhousz’s light comparison and Engelmann’s bacterial distribution collectively show that illuminated green tissue restores combustion-supporting air and evolves most oxygen in blue and red light. Which claim still requires additional isotope evidence?

19. Purified pigments P, Q and R show the following relative absorption under equal incident light.

Which conclusion is best supported by the complete dataset?

20. A chloroplast preparation has functional stromal enzymes but severely damaged thylakoid membranes. It is supplied with light, water and carbon dioxide but no external ATP or NADPH. Carbohydrate synthesis soon declines most directly because:

21. The water-splitting complex is located on the lumen-facing side of the thylakoid membrane. A non-permeating inhibitor is added to the stromal side of intact thylakoids and has little effect on oxygen evolution. When the thylakoids are ruptured before the same inhibitor is added, oxygen evolution falls sharply. Which inference is strongest?

22. Two otherwise comparable preparations give the following results.

Which conclusion integrates all three observations?

23. Match each dimension of light with the observation that tests it most directly. A Column II entry is used once.

24. In a C4 leaf, a transported four-carbon acid is decarboxylated inside a bundle-sheath cell. What is the principal immediate use of the released carbon dioxide?

25. Compare the two photosynthetic plants described below.

Which identification is correct?

26. 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:

27. 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?

28. The Calvin cycle requires ATP and NADPH for each carbon dioxide fixed. What is the requirement for fixation of carbon-dioxide molecules?

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

30. Light near is selectively prevented from exciting its corresponding reaction centre, while photosystem I remains capable of absorbing suitable light. Under non-cyclic conditions, the most direct initial disruption is:

31. 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.

32. A photosynthetic sulphur bacterium uses as its hydrogen donor and deposits elemental sulphur. Which substituted relation is consistent with van Niel’s generalised equation?

33. Granum stacks are selectively destroyed in a chloroplast, but stroma lamellae, ATP synthase and stromal Calvin-cycle enzymes remain intact. The preparation is given far-red light, external NADPH, carbon dioxide and RuBP. Which outcome is most likely?

34. In a partially covered-leaf experiment, a transparent sheet is mistakenly used instead of opaque paper. Both regions later become blue-black with iodine. The main procedural defect is that:

35. Match each thylakoid region with the feature most closely associated with it in the stated chloroplast organisation. A Column II entry is used once.

36. A C4 plant has normal Kranz anatomy, functional PEP carboxylase and normal OAA formation. A mutation prevents four-carbon acids from moving efficiently from mesophyll to bundle-sheath cells. Under high temperature, OAA accumulates in mesophyll cells, bundle-sheath carbon dioxide falls and phosphoglycolate formation increases. Which interpretation best integrates these observations?

37. During carbon fixation, one molecule of carbon dioxide combines with an unknown acceptor. A transient -carbon state forms and immediately gives rise to molecules of -carbon PGA. The unknown acceptor is most consistently identified as:

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

39. Two sealed bell jars each contain a destarched green leaf in light. One jar contains potassium hydroxide and the other contains water. Only the leaf in the water jar becomes blue-black with iodine. The strongest conclusion is:

40. Enzyme activities are measured in isolated cell fractions from a leaf.

Microscopy identifies P as cells outside the bundle sheath and Q as the chloroplast-rich ring around vascular bundles. Which interpretation is most appropriate?

41. 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.

42. Assertion: Photosystem I operates before photosystem II during non-cyclic electron flow.
Reason: The photosystems were named in the order in which they were discovered rather than their functional order.

43. Consider the following statements about the carbon-concentrating role of the C4 pathway.
I. PEP carboxylase captures inorganic carbon in mesophyll cells.
II. Four-carbon acids carry fixed carbon into bundle-sheath cells.
III. Decarboxylation raises carbon-dioxide concentration around RuBisCO.
IV. The mechanism depends on releasing oxygen beside RuBisCO.
Which combination is valid?

44. Consider the following statements about biochemical compartmentation in a C4 leaf.
I. PEP carboxylase carries out initial inorganic-carbon fixation in mesophyll cells.
II. Four-carbon acids transport fixed carbon toward bundle-sheath cells.
III. RuBisCO and the Calvin cycle operate principally in bundle-sheath cells.
IV. Both initial PEP carboxylation and the complete Calvin cycle occur in the same mesophyll cell.
Which combination is valid?

45. In van Niel’s generalised relation , conversion of into indicates that the hydrogen donor has been ______ while carbon dioxide is reduced.

46. A leaf is supplied with saturating light, abundant carbon dioxide, adequate water and a suitable temperature. Its photosynthetic rate remains at a plateau. Doubling chlorophyll content produces no measurable change, but increasing RuBisCO content raises the rate substantially. Which factor was limiting the original plateau?

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

Which comparison of net carbon gain is correct?

48. An investigator compares the following treatments after enclosed air has first been altered by a burning candle.

Which comparison most directly isolates the effect of light on plant-mediated restoration?

49. Assertion: In normal non-cyclic electron flow, photosystem I does not receive its replacement electron directly from water.
Reason: Water replaces electrons lost by photosystem II, while the interphotosystem carrier chain delivers electrons from photosystem II to oxidised photosystem I.

50. 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?