Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. Compare the two photosynthetic plants described below.

Which identification is correct?

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

3. A mutant plant fails to close its stomata during water shortage, but prolonged drought still causes severe wilting and reduced enzyme activity. Compared with its well-watered state, its photosynthesis is expected to:

4. Two grasses belong to the same plant family. Grass P has Kranz anatomy, mesophyll PEP carboxylase and OAA as its first stable product. Grass Q lacks Kranz anatomy, uses mesophyll RuBisCO directly and first forms PGA. Which conclusion is most appropriate?

5. A leaf lacks Kranz anatomy. RuBisCO occurs in mesophyll chloroplasts, PGA is the first stable fixation product, and measurable photorespiration occurs under hot conditions. The leaf is best classified as:

6. 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:

7. Assertion: Severe wilting can reduce photosynthesis even when some carbon dioxide remains available within the leaf.
Reason: Wilting can reduce exposed leaf area and depress metabolic activity in photosynthetic tissues.

8. Use the chloroplast arrangement described below. Region P consists of stacked thylakoids, Region Q is the surrounding stroma, Body R is a starch grain within Q, and Particles S are stromal ribosomes. If stromal carbon-fixation enzymes are selectively inhibited while thylakoids remain functional, which result is expected first?

9. 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?

10. A mutation prevents chloroplast movement but leaves pigment composition, thylakoid structure and stromal enzymes functional. Compared with normal mesophyll cells under changing light, the mutant cells would most likely show:

11. Arrange the following events in the early C4 pathway.
P. A four-carbon acid moves to a bundle-sheath cell.
Q. PEP carboxylase fixes inorganic carbon in a mesophyll cell.
R. OAA is formed.
S. OAA is converted into a transportable four-carbon acid.

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

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

13. 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?

14. Two plants have the same gross rate of carbon fixation, but Plant P releases considerably more carbon dioxide through photorespiration than Plant Q. If respiratory losses and other conditions are otherwise comparable, which prediction is most justified?

15. Within the approximately linear low-light region, a leaf has a relative photosynthetic rate of units at a light intensity of units. If light intensity rises to units and all other factors remain non-limiting, the most reasonable first approximation is a rate near:

16. C3 and C4 leaves are first measured under low light, where carbon-dioxide enrichment causes little change. They are then moved to high light without altering temperature or water supply. Which response to increased carbon dioxide is expected now?

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

18. Photosynthetic rates are measured under four treatments.

Which comparison most directly isolates the effect of temperature?

19. Assertion: OAA is the primary carbon-dioxide acceptor in the C4 pathway.
Reason: Initial fixation in mesophyll cells uses -carbon PEP and produces -carbon OAA.

20. Photosynthesising algae receive a brief pulse of , after which unlabelled carbon dioxide is supplied. Label appears first in PGA, later in triose phosphate and eventually in RuBP, while the total RuBP concentration remains approximately constant. Which inference is strongest?

21. Arrange the following discoveries from the broadest environmental observation to the most specific evidence about atomic origin.
P. A plant restores enclosed air altered by a candle or animal.
Q. Restoration occurs in light and is associated with green tissue.
R. Blue and red wavelengths produce the greatest local oxygen evolution.
S. Oxygen isotope from labelled water appears in the evolved gas.

22. 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?

23. 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?

24. Plants are grown under identical suitable light, temperature and water conditions.

Which conclusion is best supported?

25. 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.

26. 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.

27. A graph constructed from Engelmann’s observations plots wavelength on the horizontal axis and density of aerobic bacteria beside the algal filament on the vertical axis. High peaks occur in the blue and red regions, with a low value in much of the green region. The graph most directly represents:

28. 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?

29. Assertion: Raising the carbon-dioxide concentration around RuBisCO can reduce photorespiration.
Reason: Carbon dioxide and oxygen compete for the RuBisCO active site, and carbon dioxide favours the carboxylase reaction.

30. Chloroplasts are separated into a pigment-containing membrane fraction and a soluble stromal fraction. The membrane fraction produces ATP and NADPH in light but does not fix carbon dioxide. The stromal fraction fixes carbon dioxide only when ATP and NADPH are added. The strongest inference is:

31. A chloroplast is separated into three functional fractions. Fraction G contains granal membranes with both photosystems. Fraction L contains stroma lamellae supporting cyclic flow around photosystem I. Fraction S contains stromal enzymes. Under white light with water, ADP, inorganic phosphate, , carbon dioxide and RuBP, which minimum combination can produce both oxygen and carbohydrate?

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

33. 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:

34. If molecules of RuBP each undergo one successful carboxylation event, how many PGA molecules are formed, and how many carbon atoms do those PGA molecules contain altogether?

35. Arrange the following electron-replacement relations in the order that maintains non-cyclic electron flow.
P. An electron from the PS-II carrier chain reduces oxidised .
Q. Water supplies an electron to oxidised .
R. An electron from excited photosystem I reaches the pathway reducing .
S. Excited photosystem II transfers an electron into the carrier chain.

36. A photosynthetic bacterium grows in illuminated, oxygen-free water containing carbon dioxide and hydrogen sulphide. It forms organic matter and deposits sulphur granules but releases no oxygen. The observations indicate that:

37. A destarched leaf remains attached to a plant. One portion is enclosed in an airtight flask containing potassium hydroxide without touching it, while the rest stays exposed to air. Both portions receive light. The comparison primarily tests:

38. 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?

39. Despite normal leaf area and adequate light, water, temperature and carbon dioxide, the mesophyll cells contain very few chloroplasts with greatly reduced chlorophyll. The most likely effect is:

40. 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?

41. Two curves are plotted against wavelength. Curve P records light absorbed by chlorophyll pigments, while Curve Q records aerobic-bacterial accumulation around Engelmann’s illuminated alga. Both show prominent blue and red regions. Which interpretation is most appropriate?

42. Paper chromatography produces a yellow-orange carotenoid band. A claim is made that carotenoids must absorb orange light most strongly since the separated band appears orange. Which evaluation is scientifically appropriate?

43. Compare two photosynthetic systems.

Which interpretation follows from the complete comparison?

44. A three-carbon compound produced by bundle-sheath decarboxylation moves back to the mesophyll. The next essential event that permits repeated initial carbon fixation is:

45. 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:

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

47. A report claims that Sachs’s starch observations prove chlorophyll itself becomes starch in one direct light-driven reaction. Which correction is most accurate?

48. 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?

49. A chloroplast has accumulated sufficient NADPH, but its stromal carbon reactions remain limited by an ATP shortage. Water availability and photosystem-I function are normal. Which adjustment most directly corrects the imbalance without increasing oxygen evolution?

50. 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?