Photosynthesis in Higher Plants Mock Test – Class 11 Biology

1. A graph plots net photosynthetic rate against oxygen concentration at fixed carbon dioxide, high light and suitable temperature. Curve P falls steeply as oxygen increases, whereas Curve Q remains nearly horizontal. Additional anatomical analysis shows that only Q possesses Kranz anatomy. Which interpretation is most appropriate?

2. At the plateau of a leaf’s light-response curve, carbon-dioxide availability remains low. Which change is most likely to raise its photosynthetic rate without increasing light further?

3. Tomato and bell-pepper plants are grown in a well-lit greenhouse with adequate water and suitable temperature. Carbon dioxide is moderately enriched within a non-damaging range. The most likely agricultural outcome is:

4. Non-cyclic electron flow must supply NADPH molecules. Assume each NADPH requires electrons and all electrons originate from photolysis according to . How many water molecules are split and oxygen molecules released?

5. 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?

6. Match each part of a C4 leaf with its spatial or functional description. A Column II entry is used once.

7. An enzyme adds carbon dioxide to RuBP under one set of conditions and oxygen to RuBP under another. Its name is completed as ribulose bisphosphate ______, reflecting these two catalytic activities.

8. Four treatments are arranged as shown.

The most suitable pair for isolating the effect of carbon-dioxide availability while keeping enclosure and light conditions comparable is:

9. Chloroplasts are treated so that all thylakoid membranes are destroyed, while stromal enzymes remain functional. The preparation is placed in darkness and supplied with carbon dioxide, RuBP, ATP and NADPH. Which outcome is most likely during the initial incubation?

10. Isolated stroma is incubated in darkness with carbon dioxide, RuBP, ATP and NADPH and forms PGA followed by triose phosphate. In a parallel preparation lacking NADPH, PGA forms but accumulates and triose-phosphate production is very low. Which conclusion best integrates the results?

11. 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?

12. Two leaves have equal area and receive identical environmental conditions. Leaf P has well-developed mesophyll with many chloroplasts, while Leaf Q has poorly developed mesophyll with fewer chloroplasts. Which prediction is most justified?

13. 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:

14. Two graphs use wavelength on the horizontal axis. Graph P plots light absorbed by chlorophyll a, whereas Graph Q plots oxygen evolved by an illuminated green tissue. Graph P and Graph Q represent, respectively:

15. A stromal preparation has ATP and NADPH available, with sufficient RuBP, carbon dioxide and functional enzymes. Using the requirement of ATP and NADPH per carbon dioxide, the maximum number of carbon-dioxide molecules that can be fixed is:

16. Paper chromatography of a leaf extract reveals four distinct pigment bands. An investigator declares that the band moving farthest must represent the chief photosynthetic pigment. Which additional evidence would be most relevant for evaluating this claim?

17. Assertion: The term dark reaction is misleading when interpreted to mean that carbon fixation requires darkness.
Reason: Carbon reactions are not directly driven by photons, but they depend on ATP and NADPH normally produced in light.

18. 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:

19. 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:

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

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

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

22. Net photosynthetic rate is plotted against oxygen concentration for a C3 plant and a C4 plant at high temperature, high light and fixed carbon dioxide. Oxygen concentration is then lowered substantially. Which response is expected?

23. 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.

24. 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?

25. Twelve RuBP molecules react with RuBisCO under two gaseous conditions. In Condition P, undergo carboxylation and undergo oxygenation. In Condition Q, undergo carboxylation and undergo oxygenation. Which change from P to Q is correct?

26. An illuminated aquatic green plant releases bubbles that are collected in an inverted tube. The collected gas supports the renewed glowing of a splint. The most justified inference is that:

27. 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:

28. After addition of an inhibitor to an actively cycling chloroplast, the following time-course is observed: RuBP declines steadily, PGA continues to appear briefly, triose phosphate is initially detectable but later falls, and ATP plus NADPH remain available. Which step is most directly inhibited?

29. 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:

30. Three chloroplast fractions produce the following observations.

Which identification is correct?

31. 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?

32. Arrange the events in the broad order followed during non-cyclic light reactions.
P. Reaction-centre electrons become excited.
Q. Photosynthetic pigments absorb light.
R. Electrons pass through carriers and contribute to NADP reduction.
S. ATP and NADPH become available for carbon reactions.

33. During the reduction phase of the Calvin cycle, evaluate the following statements.
I. ATP supplies energy for reactions involving PGA.
II. NADPH supplies reducing power.
III. Reactions lead toward formation of triose phosphate.
IV. Photolysis directly converts PGA into RuBP.
Which combination is valid?

34. 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:

35. 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?

36. Which statement best represents how external factors affect photosynthesis under natural conditions?

37. Photosynthesis of each leaf increases linearly below light units according to , and saturates at rate units per leaf above that intensity. Plant P has leaves receiving light units each. Plant Q has leaves receiving units each. Assume all other factors are non-limiting and leaf rates are additive. Which comparison is correct?

38. Equal areas of four leaf tissues are examined under identical illumination.

If P and R are mesophyll tissues, which prediction is most justified?

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

40. RuBisCO is exposed to four gaseous environments while temperature and all other conditions remain suitable.

Which environment should most strongly favour carboxylation over oxygenation?

41. Consider the following statements about carbon fixation in C3 and C4 plants.
I. PGA is the first stable product in the C3 pathway.
II. OAA is the first stable product of initial fixation in the C4 pathway.
III. RuBP and PEP are the respective primary carbon-dioxide acceptors.
IV. The labels C3 and C4 indicate the carbon number of the primary acceptor.
Which combination is valid?

42. 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:

43. 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:

44. Complete the overall relation for oxygenic photosynthesis in a green plant.

45. Two chloroplast fractions produce the following results.

Which interpretation is correct?

46. A green plant is supplied with water, carbon dioxide and mineral nutrients, but it receives no usable light. The most immediate photosynthetic consequence is:

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

48. A specific inhibitor stops water splitting but leaves both reaction centres capable of absorbing light for a brief period. Which combination of changes is expected as non-cyclic electron flow continues to be attempted? A. Oxygen evolution rises, lumen protons increase and remains reduced B. Oxygen evolution falls, but electron replacement and lumen acidification remain normal C. Oxygen evolution, electron replacement in PS II and direct lumen proton input all decrease D. NADPH production rises as water is no longer competing with Answer: C. Oxygen evolution, electron replacement in PS II and direct lumen proton input all decrease Explanation: Photolysis supplies three linked outputs. Oxygen evolution depends on the oxidation of water, replacement electrons are delivered to oxidised PS II, and protons are released into the thylakoid lumen. Blocking water splitting removes all three contributions. The PS-II reaction centre may absorb photons initially, but after donates electrons, it cannot be reduced efficiently without water-derived replacement electrons. Electron flow from PS II therefore declines, and downstream NADPH formation also decreases rather than increases. The lumen may still receive some protons through carrier-associated transport, but the direct photolytic contribution is lost. Continued non-cyclic electron flow ultimately fails because PS II cannot replace its lost electrons, release oxygen or contribute lumen protons through photolysis.

146. 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.

49. Four regions of a destarched leaf are exposed to the following conditions for the same period.

Which conclusion is strongest?

50. Match each experimental component with its principal purpose. A Column II entry is used once.