Respiration in Plants Mock Test – Class 11 Biology

1. Assertion: Conversion of pyruvate into acetyl CoA is a substrate-level phosphorylation reaction.
Reason: During this conversion, one carbon is released as and is reduced to .

2. All three carbon atoms of one pyruvate molecule are radioactively labelled. After one normal link reaction, the labelled carbon is expected to be distributed as:

The expected distribution is:

3. A respirometric setup reports that a tissue releases of carbon dioxide and consumes of oxygen. A student instead divides ATP formed by oxygen volume. Which correction is required?

4. Five glucose molecules complete both ATP-investment reactions and split into ten PGAL-equivalent streams. All ten streams form BPGA and , but only six streams complete both substrate-level ATP-forming reactions and reach pyruvate. The remaining four stop before BPGA transfers phosphate to ADP. What is the resulting glycolytic record?

5. Equal masses of living plant tissue are cut into thin slices and thick blocks. Both are placed in air under identical conditions. Oxygen reaches the centres of thin slices more rapidly, while the centres of thick blocks become oxygen-deficient. The result supports the conclusion that:

6. A waterlogged germinating seed has abundant stored carbohydrate but limited access to oxygen. Ethanol and carbon dioxide accumulate, the seed gains only a small amount of ATP per glucose and reserve consumption becomes rapid. Which explanation fits all observations?

7. All six carbons of one glucose molecule are labelled. Which profile correctly describes the final labelled-carbon distribution under the three stated pathways?

8. Arrange the events that connect sucrose with the common glycolytic pathway.
P. Sucrose becomes available to a plant cell.
Q. Invertase hydrolyses the disaccharide.
R. Glucose and fructose are released.
S. The monosaccharides enter the glycolytic route after suitable processing.

9. Arrange the following events in the order that links sunlight to energy use in a non-green plant cell.
P. Light energy is captured by photosynthetic tissue.
Q. Organic carbohydrate is synthesised.
R. Organic food reaches or is stored in the non-green cell.
S. Respiration transfers part of the food's chemical energy to ATP.

10. A plant fixes labelled carbon dioxide into leaf carbohydrate. An insect eats the leaf, and a bird later eats the insect. Label is subsequently detected in carbon dioxide released by the bird. The most appropriate interpretation is:

11. An actively respiring yeast culture is shifted from an oxygenated medium to an oxygen-free medium while glucose remains abundant. The most appropriate pathway-level prediction is:

12. Carbohydrate supply is compared in three plant tissues.

The combined record best supports which conclusion?

13. A leaf admits oxygen through stomata, after which its cells oxidise organic molecules and form ATP. The relation between the two events is best stated as:

14. A cell must obtain equivalents. Under the theoretical values of per aerobically oxidised glucose and per fermented glucose, how many glucose molecules are required by the two pathways?

15. Consider the following statements about oxidative phosphorylation.
I. It links respiratory electron transfer with phosphorylation of ADP.
II. Its immediate energy source is the proton gradient across the inner mitochondrial membrane.
III. It forms ATP by direct phosphate transfer from a glycolytic intermediate.
IV. It depends on redox energy released as electrons move toward oxygen.

16. Assertion: Complete aerobic oxidation of pyruvate in a eukaryotic cell occurs entirely in the cytoplasm.
Reason: Pyruvate formed by glycolysis must enter the mitochondrial matrix before oxidative decarboxylation and the TCA cycle proceed.

17. Leaves, young stems and roots of an intact plant are enclosed in separate transparent chambers without damaging their connections. Each chamber shows its own change in oxygen and carbon-dioxide concentration. The strongest inference is:

18. A drug blocks the ATP-dependent conversion of fructose-6-phosphate into fructose-1,6-bisphosphate but leaves earlier reactions functional.

The expected metabolite pattern is:

19. Gas exchange is recorded for four aerobic samples.

Which sample is most consistent with complete oxidation of carbohydrate?

20. Assertion: Coenzyme A is released during formation of citrate from acetyl CoA and oxaloacetate.
Reason: Citrate contains a six-carbon skeleton.

21. Evaluate the following statements about the role of oxygen in aerobic respiration.
I. It receives electrons at the terminal end of the mitochondrial carrier chain.
II. Its reduction contributes to formation of water.
III. It is consumed directly during every reaction of glycolysis and the TCA cycle.
IV. Its absence causes upstream electron carriers to remain increasingly reduced.

22. Three inhibitors are classified according to their primary respiratory effect.
P. Hexokinase inhibitor
Q. Complex-IV inhibitor
R. Alcohol-dehydrogenase inhibitor in anaerobic yeast
Which classification is correct?

23. Assertion: Oxidative phosphorylation is the direct transfer of phosphate from phosphoenolpyruvate to ADP.
Reason: Oxidative phosphorylation uses energy from respiratory electron transfer to create proton-motive conditions that drive ATP synthesis.

24. Two oxidation processes are compared.

Process P and Process Q are, respectively:

25. Rates of several processes are measured in the same aerobic cell during one minute.

Which interpretation best explains why a simple sequential balance sheet may not equal the cell’s measured outcome?

26. One glucose molecule completes ATP investment and cleavage, but one of its two triose streams is then blocked before both ATP-producing reactions. The other triose stream completes glycolysis normally. What is the net direct ATP result?

27. Arrange the four-carbon intermediates in the order leading back to oxaloacetate.
P. Succinate
Q. Fumarate
R. Malate
S. Oxaloacetate

28. Assertion: Oxidative phosphorylation and photophosphorylation both use a proton gradient to support ATP synthesis.
Reason: The original energy establishing the gradient comes from respiratory redox reactions in oxidative phosphorylation and from light-driven reactions in photophosphorylation.

29. Arrange the events of alcoholic fermentation in their correct order.
P. Pyruvate decarboxylase acts on pyruvate.
Q. Acetaldehyde and are formed.
R. Alcohol dehydrogenase transfers reducing equivalents to acetaldehyde.
S. Ethanol forms while is regenerated.

30. A two-step pathway is described. Reaction P converts pyruvate into a compound with release of . Reaction Q converts the compound into ethanol while becomes . P and Q are catalysed by:

31. Four respiratory profiles are compared.

Which profile consistently represents predominant aerobic fat respiration?

32. Match each TCA event with its principal outcome. A Column II entry is used once.

33. Evaluate the following propositions about glycolysis.
I. It occurs in the cytoplasm.
II. One glucose molecule forms two molecules of pyruvic acid.
III. It completely oxidises all glucose carbon to carbon dioxide.
IV. It occurs in organisms using either aerobic or anaerobic metabolism.

34. Arrange the following events associated with the terminal ATP-producing step of glycolysis.
P. Two PEP molecules are available per glucose.
Q. Each PEP transfers a phosphate group to ADP.
R. ATP is formed through substrate-level phosphorylation.
S. Two pyruvate molecules remain as the carbon products.

35. A graph plots RQ against time in a germinating seed. The curve begins near , then gradually falls and stabilises near . Which change is most consistent with this trend?

36. Use the pathway arrangement described below. Region P contains glucose, PGAL and pyruvate. An arrow carries pyruvate into Region Q, where acetyl CoA, citrate and oxaloacetate occur. Reduced carriers formed in Q transfer electrons to complexes in Boundary R, where oxygen is reduced and ATP synthase operates. Which interpretation is correct?

37. Equal amounts of glucose undergo anaerobic metabolism in yeast and oxygen-limited muscle. Which comparison is correct?

38. Equal numbers of electron pairs are supplied to intact mitochondria in two treatments. In Treatment P, the electrons enter from NADH through complex I. In Treatment Q, they enter from succinate-linked FADH through complex II. Oxygen consumption is equal, but Treatment P produces more ATP. The difference is best explained by:

39. Cytochrome c is selectively removed from otherwise intact mitochondria. Complex III can still reduce its normal acceptor site, and complex IV remains structurally present. The most likely outcome is:

40. Assertion: Blocking the proton channel may eventually slow respiratory electron transfer even when the electron-carrier complexes are not directly inhibited.
Reason: Continued proton translocation without proton return steepens the gradient, making further proton pumping increasingly difficult.

41. A plant tissue depleted of readily available carbohydrate continues consuming oxygen and producing ATP when supplied with an organic acid. Fat and protein mobilisation are experimentally prevented. This result classifies the organic acid as:

42. Consider the following statements about the stated ATP yields of respiratory electron donors.
I. Oxidation of one NADH is assigned .
II. Oxidation of one FADH is assigned .
III. Both donors produce identical yields since their electrons reach oxygen.
IV. Their different entry points help explain the difference in assigned yield.

43. Consider the following statements about respiratory quotient.
I. Carbon-dioxide volume forms the numerator.
II. Oxygen-consumption volume forms the denominator.
III. RQ is ordinarily interpreted for aerobic respiration.
IV. ATP production is not included directly in its calculation.

44. A mitochondrial preparation supplied continuously with acetyl CoA shows the following changes: citrate rises markedly, isocitrate remains very low, alpha-ketoglutarate and succinyl CoA decline, and carbon-dioxide production falls. Which reaction is most likely impaired?

45. Arrange the electron-transfer route followed by reducing equivalents associated with succinate oxidation.
P. Complex II
Q. Ubiquinone
R. Complex III
S. Cytochrome c
T. Complex IV
U. Oxygen

46. Arrange the events by which protein-derived carbon enters respiration.
P. Protein is hydrolysed.
Q. Amino acids are released.
R. Deamination removes the amino group.
S. The remaining carbon skeleton enters at a suitable respiratory intermediate.

47. Assertion: GTP formation in the TCA cycle is classified as substrate-level phosphorylation.
Reason: Oxidation of succinate produces .

48. Preparation P contains acetyl CoA and active citrate synthase but lacks oxaloacetate. Preparation Q contains acetyl CoA and oxaloacetate but has inactive citrate synthase. Malate and are added to both preparations. Citrate forms only in P. Which interpretation is correct?

49. A pathway map shows a stored fat dividing into Component P and Component Q. P is converted into an intermediate that enters near PGAL, while Q supplies acetyl CoA for the TCA cycle. P and Q are, respectively:

50. A cell can phosphorylate glucose and form fructose-6-phosphate, but it cannot perform the second ATP-dependent phosphorylation of glycolysis. The most likely consequence is: