Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. Two illuminated plant preparations are supplied with isotopes.

Which conclusion is justified by the combined evidence?

2. After a pulse of , an illuminated chloroplast accumulates labelled PGA but forms very little labelled triose phosphate. ATP concentration is normal, NADPH concentration is very low, and addition of external NADPH causes labelled triose phosphate to appear rapidly. Which conclusion is best supported?

3. A graph plots relative product formation against wavelength from to . Beyond , ATP formation remains measurable, but oxygen evolution and NADPH production fall sharply. The pattern is best explained by:

4. A carbon-dioxide concentration of is expressed as a volume fraction in . Which conversion and interpretation match the C3–C4 comparison?

5. Consider the following statements about temperature and photosynthesis.
I. Enzyme-controlled carbon reactions are strongly influenced by temperature.
II. Light absorption and primary photochemical events are generally less temperature-sensitive than stromal enzyme reactions.
III. Temperature can alter the overall rate even when light and carbon dioxide remain unchanged.
IV. Every photosynthetic reaction responds equally to the same temperature change.
Which combination is valid?

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

7. A variegated leaf is exposed to light without being destarched first. Why does this weaken the interpretation of the later iodine test?

8. 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?

9. Granal thylakoids are more suitable than stroma lamellae for complete non-cyclic electron flow mainly because granal membranes:

10. PEP carboxylase is completely inhibited in a C4 leaf. Investigators then supply a high carbon-dioxide concentration directly to isolated bundle-sheath cells while ATP, NADPH, RuBP and RuBisCO remain functional. Which result is most likely during the short experiment?

11. Match each observation with the strongest interpretation. A Column II entry is used once.

12. 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:

13. Use the circular arrangement described below. Structure P is a -carbon compound that accepts carbon dioxide. Structure Q is the resulting unstable -carbon state. Structure R represents identical -carbon stable products. P, Q and R correspond to:

14. A mutation makes C4 bundle-sheath walls highly permeable to carbon dioxide while leaving four-carbon-acid formation, transport and decarboxylation functional. Under hot conditions, the most likely result is:

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

Which comparison of net carbon gain is correct?

16. Which experimental design most effectively isolates light quality as the independent variable?

For S, temperature, carbon dioxide, water status and leaf condition are also identical.

17. 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?

18. 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?

19. 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:

20. 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?

21. Two temperature-response curves are obtained under high light, adequate water and sufficient carbon dioxide. Curve P reaches its maximum near and declines above . Curve Q reaches its maximum near and remains relatively high at . Which identification is most appropriate?

22. 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.

23. Arrange the events of cyclic photophosphorylation under far-red illumination.
P. Carrier activity establishes a proton gradient across the thylakoid membrane.
Q. absorbs light and donates an excited electron.
R. The electron travels through cyclic carriers and returns toward photosystem I.
S. Protons return through ATP synthase and ATP is formed.

24. Four light-dependent pathways show the following outputs.

Which identification is valid?

25. 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?

26. The following events occur in a light-harvesting complex.
P. An accessory pigment absorbs a photon.
Q. Excitation energy reaches reaction-centre chlorophyll a.
R. A high-energy electron moves from the reaction centre to the primary acceptor.
S. The antenna pigment returns to its ground state.
At which transition does the process change from excitation-energy transfer to electron transfer?

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

28. Consider the following statements about carbon dioxide as a photosynthetic factor.
I. Its atmospheric concentration is relatively low and commonly limits photosynthesis.
II. Moderate enrichment up to about can increase carbon fixation under suitable conditions.
III. Prolonged exposure to substantially higher concentrations may become damaging.
IV. Carbon-dioxide enrichment always increases photosynthesis equally, even under very low light.
Which combination is valid?

29. A chloroplast has sufficient NADPH but an ATP shortage. Cyclic electron flow around photosystem I is stimulated, yet the proton channel is simultaneously blocked. Which outcome is most likely?

30. 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.

31. 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?

32. The commonly cited approximate atmospheric carbon-dioxide concentration is:

33. A photosystem is described as a protein-associated pigment complex containing hundreds of surrounding pigment molecules and one centrally functional chlorophyll a molecule connected to a primary electron acceptor. The surrounding pigments and the specialised chlorophyll a function, respectively, as:

34. Arrange the following events linking light absorption with carbohydrate formation.
P. Protons return through ATP synthase.
Q. Photosystems initiate electron flow.
R. ATP and NADPH become available in the stroma.
S. Carbon dioxide is fixed and reduced.
T. A proton gradient develops across the thylakoid membrane.

35. Consider the following statements about non-cyclic photophosphorylation.
I. Both photosystem II and photosystem I participate.
II. Electrons ultimately reduce .
III. Water supplies replacement electrons and oxygen is evolved.
IV. ATP and NADPH are both formed.
Which combination is valid?

36. An absorption curve for purified chlorophyll a and an action-spectrum curve for an intact leaf share major blue and red peaks, but the action curve is higher than the chlorophyll a curve in some intermediate wavelengths. The mismatch most strongly indicates that:

37. A drought-stressed leaf initially has closed stomata, low internal carbon dioxide and reduced photosynthesis. Investigators then force the stomata open and restore internal carbon dioxide to the control value. The leaf remains severely wilted, stromal enzyme activity stays low and photosynthesis recovers only slightly. Which conclusion is strongest?

38. Compare two photosynthetic systems.

Which interpretation follows from the complete comparison?

39. The water-splitting complex of photosystem II is completely inhibited, and the leaf is supplied with a very high external oxygen concentration. Oxygen evolution, ATP formation and NADPH production remain low. Why does external oxygen fail to rescue the pathway?

40. During illumination, an experimental treatment rapidly increases proton concentration in the stroma until it nearly equals that in the thylakoid lumen. Electron carriers, water splitting and ATP synthase remain structurally intact. Which immediate response is most likely?

41. Assertion: Ingenhousz demonstrated that light is required for plant-mediated restoration of altered air.
Reason: Priestley had earlier observed that plants could restore air changed by burning and animal respiration.

42. Examine the proposed carbon relations.

Which proposal correctly describes initial carbon fixation?

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

44. During an experiment, non-cyclic electron flow releases molecules of oxygen. Assume each oxygen molecule corresponds to the electron supply required to form NADPH molecules. The stroma has ATP available, and fixation of each carbon-dioxide molecule requires ATP and NADPH. What is the maximum carbon-dioxide fixation and the ATP remaining?

45. 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?

46. Two genetically different varieties of the same crop are grown from germination under identical light, temperature, water, mineral supply and carbon-dioxide conditions. They develop different chlorophyll contents and maximum photosynthetic rates. The result most directly supports the influence of:

47. Consider the following statements about photosynthetic light-harvesting complexes.
I. Their pigments are associated with proteins in the thylakoid membrane.
II. Light-harvesting complexes occur in association with both photosystem I and photosystem II.
III. Antenna pigments funnel excitation energy toward a specialised reaction-centre chlorophyll a.
IV. Every antenna pigment transfers its own electron directly to the primary electron acceptor.
Which combination is valid?

48. Compare cyclic and non-cyclic photophosphorylation.

A treatment prevents electrons from returning to but leaves the complete PS-II-to-NADP route functional. Which shift is expected?

49. A researcher performs two measurements. In Setup P, a purified leaf-pigment extract is exposed to different wavelengths and the fraction of light absorbed is recorded. In Setup Q, an intact illuminated leaf is exposed to the same wavelengths and oxygen evolution is measured. The two setups are designed to compare:

50. Four chloroplast preparations are supplied with illuminated thylakoids and the substances shown.

Which preparation contains the complete immediate requirements for normal NADPH formation?