Correct Answer: (a)
F₀ is the transmembrane channel for proton flow; F₁ is a peripheral protein on the matrix side and contains the catalytic site for ATP synthesis. This structural organisation is critical for chemiosmosis.
Q2. Assertion: RQ for fats is less than 1.
Reason: Fats require more oxygen for oxidation compared to carbohydrates.
Correct Answer: (a)
Fats have a higher proportion of hydrogen and lower oxygen content, so they need more O₂ per molecule for complete oxidation. This results in less CO₂ produced relative to O₂ consumed, hence RQ < 1. The reason correctly explains the lower RQ.
Q3. Regarding 'TCA Cycle', which are correct? (i) It occurs in the mitochondrial matrix. (ii) Citric acid is the first product. (iii) GTP is synthesized in the cycle.
Correct Answer: (a)
The TCA cycle enzymes are in the matrix; citrate is the first product; and GTP (or ATP) is produced by substrate-level phosphorylation. All statements are correct.
Q4. The enzyme that converts sucrose into glucose and fructose is:
Correct Answer: (b)
Invertase (also called sucrase) hydrolyses the glycosidic bond in sucrose to yield glucose and fructose. Hexokinase phosphorylates glucose; enolase acts in glycolysis; phosphofructokinase is a key regulatory enzyme. Thus invertase is the correct enzyme for sucrose breakdown.
Q5. Regarding 'NADH oxidation', which statements are true? (i) One NADH yields 3 ATP. (ii) Occurs at Complex I of ETS. (iii) Requires Oxygen as the terminal acceptor.
Correct Answer: (a)
NADH donates electrons to Complex I, generating 3 ATP, and ultimately electrons are transferred to O₂. All three statements are true.
Q6. Match the substrate with its RQ value:
Column-I (Substrate)
Column-II (RQ)
A. Carbohydrates
(I) 0.7
B. Proteins
(II) 1.0
C. Fats (Tripalmitin)
(III) 0.9
Correct Answer: (a)
Carbohydrates have RQ = 1.0; proteins ≈ 0.9; fats ≈ 0.7. These values reflect the relative oxygen requirements for their oxidation.
Q7. Which statements about 'Yeasts' are correct? (i) Perform alcoholic fermentation. (ii) Die at 13% alcohol concentration. (iii) Are facultative anaerobes.
Correct Answer: (a)
Yeasts carry out alcoholic fermentation, are facultative anaerobes (can grow with or without O₂), and are killed by ethanol above ~13%. All statements are correct.
Q8. Which of the following is correct regarding 'Plant Respiration'? (i) Plants have no specialized organs for exchange. (ii) Each plant part takes care of its own needs. (iii) Gaseous transport between parts is very high.
Correct Answer: (a)
Plants lack respiratory organs; each part exchanges gases individually; and gas transport between parts is low because diffusion distances are short. Thus (i) and (ii) are correct, (iii) is false.
Q9. Regarding 'ETS', which are correct? (i) Complex IV contains cytochromes a and a3. (ii) Cytochrome c is a mobile carrier. (iii) It is located in the outer mitochondrial membrane.
Correct Answer: (a)
Complex IV has cytochromes a and a3; cytochrome c is a mobile carrier; but the ETS is in the inner membrane, not outer. So (i) and (ii) are correct.
Q10. Which are correct for 'Anaerobic Respiration'? (i) Only 2 ATP net gain. (ii) Ethanol and CO2 or Lactic acid are products. (iii) Occurs in cytoplasm only.
Correct Answer: (a)
Anaerobic respiration (fermentation) yields 2 ATP, produces either ethanol+CO₂ or lactate, and occurs entirely in the cytoplasm. All three statements are correct.
Q11. The TCA cycle starts with the condensation of acetyl group with ______ and water.
Correct Answer: (b)
Acetyl CoA (2-carbon) condenses with oxaloacetic acid (OAA, 4-carbon) and water to form citric acid (6-carbon), catalysed by citrate synthase. This is the first step of the TCA cycle. Succinic acid and malic acid are later intermediates, and citric acid is the product.
Q12. Which of the following is correct? (i) Melvin Calvin won the Nobel Prize in 1961. (ii) He used radioactive 14C. (iii) He mapped the pathway of carbon assimilation.
Correct Answer: (a)
Calvin received the Nobel Prize in 1961 for using ¹⁴C to trace the path of carbon in photosynthesis, establishing the Calvin cycle. All statements are correct.
Q13. How many molecules of pyruvic acid are produced from one molecule of glucose during glycolysis?
Correct Answer: (b)
During glycolysis, one molecule of glucose (6 carbons) is cleaved into two molecules of pyruvic acid (3 carbons each). This is a partial oxidation that yields a net gain of 2 ATP and 2 NADH. The number of pyruvate molecules is therefore two.
Q14. Assertion: Interkinesis lacks DNA replication.
Reason: Interkinesis is the stage between Meiosis I and Meiosis II.
Correct Answer: (b)
Interkinesis is the brief period between meiosis I and II; during this time, DNA replication does not occur because the chromosomes are already duplicated (each consists of two sister chromatids). The reason (that it is between divisions) does not explain the lack of replication; replication is absent because the S-phase has already taken place before meiosis I. Both are true but unrelated.
Q15. Match the steps in glycolysis with enzyme action:
Column-I
Column-II
A. ATP utilized
(I) Glucose to G6P
B. ATP utilized
(II) F6P to F-1,6-bisphosphate
C. ATP synthesized
(III) BPGA to PGA
D. ATP synthesized
(IV) PEP to Pyruvic acid
Correct Answer: (a)
ATP is consumed in the first two priming steps (glucose → G6P and F6P → F-1,6-BP) and produced in the last two substrate-level phosphorylations (BPGA → PGA and PEP → pyruvate).
Q16. Match the metabolic intermediate with its precursor/product:
Column-I
Column-II
A. Fats
(I) Amino acids
B. Proteins
(II) Glycerol and fatty acids
C. Fatty acids entry point
(III) Acetyl CoA
D. Glycerol entry point
(IV) PGAL
Correct Answer: (a)
Fats break into glycerol and fatty acids; proteins yield amino acids; fatty acids enter as acetyl CoA; glycerol enters as PGAL. These are key interconnections in the amphibolic pathway.
Q17. Match the following for Glycolysis products:
Product
Amount per Glucose
A. Pyruvic acid
(I) 2 molecules
B. NADH + H+
(II) 2 molecules
C. Net ATP gain
(III) 2 molecules
Correct Answer: (a)
One glucose yields 2 pyruvate, 2 NADH, and a net gain of 2 ATP (after subtracting 2 used). All three quantities are 2 molecules.
Q18. The energy currency of the cell is:
Correct Answer: (c)
ATP (adenosine triphosphate) is universally referred to as the energy currency because it stores and transfers the chemical energy released during oxidation of substrates. Glucose and pyruvic acid are fuel molecules, while NADPH is a reducing agent. ATP is directly used to drive endergonic reactions in the cell.
Q19. The Electron Transport System (ETS) is located in the:
Correct Answer: (b)
ETS is embedded in the inner mitochondrial membrane, where electron carriers (complexes I–IV) and ATP synthase are located. This arrangement creates a proton gradient across the membrane. The matrix contains TCA enzymes, while the outer membrane and cytoplasm lack the ETS components.
Q20. Assertion: Mitochondria are called 'Power Houses' of the cell.
Reason: They are the sites of ATP production in eukaryotic cells.
Correct Answer: (a)
Mitochondria are the main sites of aerobic respiration where most ATP is generated via oxidative phosphorylation. This ATP production is the primary function that earns them the nickname 'power houses'. The reason correctly links the name to the function.
Q21. Assertion: NADH is oxidized to NAD+ slowly in fermentation.
Reason: Aerobic respiration is very vigorous compared to fermentation.
Correct Answer: (b)
In fermentation, NADH is reoxidised to NAD⁺ slowly because the process is less efficient and limited by substrate availability. Aerobic respiration is indeed more vigorous but that does not explain the slow oxidation; the reason is that fermentation lacks an ETS and uses organic molecules as electron acceptors. Both statements are true but unrelated.
Q22. Assertion: Substrate level phosphorylation occurs in the TCA cycle.
Reason: GTP is synthesized during the conversion of succinyl-CoA to succinic acid.
Correct Answer: (a)
The TCA cycle has one step where succinyl-CoA is converted to succinate, coupled with substrate-level phosphorylation of GDP to GTP (or ADP to ATP in some organisms). This is a direct synthesis of high-energy phosphate from a substrate, which defines substrate-level phosphorylation. The reason correctly explains the assertion.
Q23. Assertion: Oxygen is vital for aerobic respiration.
Reason: Oxygen acts as the final hydrogen acceptor and removes hydrogen from the system.
Correct Answer: (a)
Oxygen is essential because it accepts electrons and protons at the end of the ETS, forming water and regenerating NAD⁺ and FAD. Without oxygen, the electron transport chain stops and aerobic respiration ceases. The reason accurately explains the vital role of oxygen.
Correct Answer: (a)
Fatty acids enter as acetyl CoA; glycerol as PGAL; amino acids can enter at various points including pyruvate. These are standard interconnections in the amphibolic pathway.
Q25. Assertion: Cyanobacteria can prepare their own food.
Reason: They trap light energy and convert it into chemical energy.
Correct Answer: (a)
Cyanobacteria are photosynthetic prokaryotes that use light energy to fix CO₂ into organic compounds. This autotrophic ability is directly due to their photosynthetic machinery, so the reason correctly explains how they prepare their own food.
Q26. Assertion: In fermentation, less than 7% of energy is trapped as ATP.
Reason: Fermentation is a process of complete oxidation.
Correct Answer: (c)
The assertion is true: fermentation releases only about 7% of the energy in glucose as ATP (2 ATP per glucose). However, the reason is false because fermentation is incomplete oxidation; the end products (ethanol or lactate) still contain much of the original energy. Complete oxidation occurs only in aerobic respiration.
Q27. In our skeletal muscles during exercise, pyruvic acid is reduced to ______ when oxygen is inadequate.
Correct Answer: (b)
Under anaerobic conditions in muscle cells, pyruvate is reduced to lactate by lactate dehydrogenase, using NADH to regenerate NAD⁺. This allows glycolysis to continue producing ATP. Ethanol is produced by yeast, and acetyl CoA or citric acid are aerobic products.
Q28. Correct statements about 'Glycerol' in respiration: (i) It is a simple lipid. (ii) It enters the pathway after being converted to PGAL. (iii) It is trihydroxy propane.
Correct Answer: (a)
Glycerol is a simple lipid (backbone of triglycerides), it is trihydroxy propane, and it enters glycolysis as PGAL after phosphorylation and oxidation. All are correct.
Q29. Conversion of pyruvic acid into acetyl CoA is called:
Correct Answer: (b)
The conversion of pyruvate to acetyl CoA involves oxidation (removal of electrons) and decarboxylation (release of CO₂), hence it is called oxidative decarboxylation. This reaction is catalysed by pyruvate dehydrogenase complex and is irreversible. Glycolysis is the preceding step, fermentation is anaerobic, and photophosphorylation occurs in photosynthesis.
Q30. Match the following ETS complexes:
Column-I (Complex)
Column-II (Name)
A. Complex I
(I) Cytochrome bc1 complex
B. Complex III
(II) NADH dehydrogenase
C. Complex IV
(III) ATP synthase
D. Complex V
(IV) Cytochrome c oxidase
Correct Answer: (a)
Complex I is NADH dehydrogenase; Complex III is cytochrome bc1; Complex IV is cytochrome c oxidase; and Complex V is ATP synthase. This nomenclature is standard in the electron transport chain.
Q31. In plants, glucose for glycolysis is derived from storage carbohydrates or from:
Correct Answer: (b)
In plants, the primary end product of photosynthesis is sucrose, which is translocated from source to sink tissues. Sucrose can be broken down into glucose and fructose by invertase, providing glucose for glycolysis. Starch and other storage carbohydrates also serve as sources, but sucrose is the main transport form.
Q32. Oxidation of one molecule of FADH2 produces ______ molecules of ATP.
Correct Answer: (b)
FADH₂ enters the ETS at Complex II, bypassing Complex I, thus pumping fewer protons. Consequently, it yields approximately 2 ATP per molecule. This lower yield reflects the less energetic nature of FADH₂ compared to NADH.
Q33. Regarding 'Oxidative Phosphorylation': (i) Uses energy of oxidation-reduction. (ii) Differs from photophosphorylation (which uses light). (iii) Occurs at Complex V.
Correct Answer: (a)
Oxidative phosphorylation couples electron transfer (oxidation-reduction) to ATP synthesis, uses chemical energy, and occurs at ATP synthase (Complex V). It is distinct from photophosphorylation which uses light. All are correct.
Q34. In glycolysis, ATP is utilized in how many steps?
Correct Answer: (b)
ATP is consumed in two steps of glycolysis: first, the phosphorylation of glucose to glucose-6-phosphate (hexokinase), and second, the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate (phosphofructokinase). These are the only energy-requiring steps of the pathway.
Q35. Identify the correct features of 'Mitochondrial Matrix': (i) Contains enzymes of Krebs cycle. (ii) Site of CO2 release. (iii) Contains single circular DNA and 70S ribosomes.
Correct Answer: (a)
The matrix houses TCA enzymes, is the site of CO₂ release in decarboxylations, and has its own DNA and ribosomes (semi-autonomous organelle). All statements are correct.
Q36. The F1 headpiece of ATP synthase is a ______ protein complex.
Correct Answer: (b)
The F₁ component of ATP synthase is a peripheral membrane protein, protruding into the mitochondrial matrix. It is not embedded in the lipid bilayer; it is loosely attached to the membrane. F₀ is the integral membrane domain that forms the proton channel.
Q37. The breaking of C-C bonds of complex compounds through oxidation within cells to release energy is called:
Correct Answer: (b)
Respiration is defined as the oxidative breakdown of C-C bonds in complex organic molecules, releasing energy that is trapped as ATP. This process occurs in all living cells and is distinct from photosynthesis, digestion or transpiration. It is the central metabolic pathway for energy production in plants and animals alike.
Q38. The first member of the TCA cycle is:
Correct Answer: (d)
Oxaloacetic acid (OAA) is the molecule that accepts the acetyl group and is regenerated at the end of each cycle; hence it is considered the first member. Citric acid is the first product formed, but OAA is the starting compound that condenses with acetyl CoA. Isocitrate and succinyl-CoA are downstream intermediates.
Q39. Assertion: Plant cells use a step-wise strategy for glucose catabolism.
Reason: This ensures that not all liberated energy goes out as heat.
Correct Answer: (a)
Glucose is oxidised in multiple small steps, each releasing a manageable amount of energy. This allows the cell to capture that energy in ATP rather than releasing it all as heat in a single combustion reaction. The stepwise strategy is indeed the reason for efficient energy conservation.
Q40. Correct statements about 'Proton Gradient': (i) Created across the thylakoid/mitochondrial membrane. (ii) Protons move down the gradient into the matrix to make ATP. (iii) 4H+ pass for each ATP produced.
Correct Answer: (a)
Proton gradients are established across membranes in mitochondria and chloroplasts; their flow through ATP synthase drives ATP synthesis, with about 4 H⁺ per ATP in chloroplasts and mitochondria. All statements are correct.
Q41. Assertion: ATP acts as the energy currency of the cell.
Reason: Energy released by oxidation in respiration is trapped as chemical energy in the form of ATP.
Correct Answer: (a)
ATP is the common energy carrier that couples exergonic and endergonic reactions. The energy liberated during oxidation of substrates is conserved by converting ADP and Pi to ATP. This ATP then drives biosynthetic work, transport and mechanical work in cells.
Q42. Which statements regarding 'ATP synthesis' are true? (i) It is linked to the development of a proton gradient across a membrane. (ii) Protons accumulate in the intermembrane space of mitochondria. (iii) Energy comes from the movement of protons through the F0 channel.
Correct Answer: (c)
ATP synthesis in mitochondria is driven by the proton motive force: protons are pumped to the intermembrane space, creating a gradient, and their flow back through F₀ powers ATP synthase. All three statements are correct.
Q43. The first step of glycolysis involves the phosphorylation of glucose to glucose-6-phosphate by:
Correct Answer: (b)
Hexokinase catalyses the transfer of a phosphate group from ATP to glucose, forming glucose-6-phosphate. This is the first committed step of glycolysis and traps glucose inside the cell. Pyruvate kinase acts later in the pathway, aldolase splits fructose-1,6-bisphosphate, and isomerase converts glucose-6-phosphate to fructose-6-phosphate.
Q44. Yeasts poison themselves to death when the concentration of alcohol reaches about:
Correct Answer: (c)
Ethanol is toxic to yeast cells; when its concentration builds up to approximately 13% (v/v), it disrupts membrane integrity and enzyme function, leading to cell death. This limit is exploited in brewing and winemaking to control alcohol content.
Q45. The scheme of glycolysis was given by:
Correct Answer: (b)
Glycolysis is also known as the EMP pathway, named after Embden, Meyerhof and Parnas who elucidated its steps. Calvin, Bassham and Benson worked on the Calvin cycle; Hans Krebs described the TCA cycle; Singer and Nicolson proposed the fluid mosaic model. The EMP pathway is the universal initial step of glucose breakdown.
Q46. Match the cycle/pathway with synonyms:
Column-I
Column-II
A. Glycolysis
(I) EMP Pathway
B. Citric Acid Cycle
(II) TCA Cycle
C. Citric Acid Cycle
(III) Krebs Cycle
Correct Answer: (a)
Glycolysis is also called the EMP pathway; the citric acid cycle is known as TCA or Krebs cycle. These are common synonyms used interchangeably.
Q47. The final hydrogen acceptor in aerobic respiration is:
Correct Answer: (c)
Oxygen is the terminal electron (and hydrogen) acceptor in aerobic respiration. It combines with electrons and protons to form water. NAD⁺ and FAD are temporary carriers, and cytochrome a3 is a component of Complex IV but not the final acceptor.
Q48. Match the following for 38 ATP calculation:
Assumption
Truth in living system
A. Sequential pathway
(I) Not really valid
B. No intermediates used
(II) Not really valid
Correct Answer: (a)
The classic 38 ATP calculation assumes a sequential pathway with no intermediates withdrawn; both are oversimplifications because the pathway is integrated and intermediates are used for biosynthesis, so both assumptions are not valid in vivo.
Q49. The first process of aerobic respiration (oxidation of pyruvate) takes place in the:
Correct Answer: (b)
The oxidative decarboxylation of pyruvate to acetyl CoA, as well as the TCA cycle, occur in the mitochondrial matrix. The matrix contains the necessary enzymes and cofactors. The inner membrane houses the ETS, and the intermembrane space is involved in proton accumulation.
Q50. Match the following for aerobic respiration events:
Event
Description
A. Step-wise removal of H atoms
(I) Leaves 3 molecules of CO2
B. Passing on of electrons
(II) To molecular O2
Correct Answer: (a)
In aerobic respiration, the stepwise removal of hydrogen atoms (dehydrogenation) is associated with decarboxylation steps that release CO₂, and the electrons are ultimately passed to O₂. This matching follows the overall process of pyruvate oxidation.
Q51. Assertion: Lenticels are used for gaseous exchange in stems.
Reason: Living cells in woody stems are organized in thin layers beneath the bark.
Correct Answer: (b)
Lenticels are indeed pores in the bark that allow gas exchange. The presence of living cells in thin layers beneath the bark is true but does not explain why lenticels form; they are actually openings through the bark. Hence both statements are true but the reason is not a correct explanation of the assertion.
Q52. Assertion: Pure proteins are never used as respiratory substrates.
Reason: Respiratory substrates are often more than one in living organisms.
Correct Answer: (d)
The assertion is false because proteins can be used as respiratory substrates under starvation conditions, after being broken down to amino acids. The reason is true—organisms typically use a mix of carbohydrates, fats and proteins—but it does not support the false assertion. Hence the correct option is 'Assertion is false but reason is true'.
Q53. Assertion: The TCA cycle is also called the Citric Acid Cycle.
Reason: The first stable product of the cycle is Citric acid.
Correct Answer: (a)
The TCA cycle is named after citric acid because citrate is the first identifiable product formed when acetyl CoA condenses with OAA. This naming is directly based on the first stable intermediate, making the reason a correct explanation.
Q54. Identify the correct statements for 'Glycolysis': (i) It involves partial oxidation of glucose. (ii) It results in two molecules of pyruvic acid. (iii) It occurs in all living organisms.
Correct Answer: (c)
Glycolysis partially oxidises glucose to two pyruvates, is universal among living organisms, and does not require oxygen. All three statements are correct.
Q55. In the ETS, Complex IV refers to:
Correct Answer: (c)
Complex IV is cytochrome c oxidase, which transfers electrons from cytochrome c to molecular oxygen, reducing O₂ to water. Complex I is NADH dehydrogenase, Complex III is cytochrome bc1, and Complex V is ATP synthase. Each complex has a specific role in electron transfer.
Q56. Assertion: The inner mitochondrial membrane contains the ETS.
Reason: The mitochondrial matrix is the site for glycolysis.
Correct Answer: (c)
The assertion is correct: the ETS is located in the inner mitochondrial membrane. However, the reason is false because glycolysis occurs in the cytoplasm, not the mitochondrial matrix. The matrix is the site for the TCA cycle and oxidative decarboxylation of pyruvate.
Q57. Assertion: In plants, glucose is often derived from sucrose.
Reason: Sucrose is the end product of photosynthesis.
Correct Answer: (a)
Photosynthesis produces sucrose, which is the major transport sugar in plants. This sucrose is translocated to non-photosynthetic tissues where it is broken down into glucose and fructose for glycolysis. Thus the reason correctly explains why sucrose is a source of glucose.
Q58. During glycolysis, NADH + H+ is formed when PGAL is converted to:
Correct Answer: (b)
The conversion of 3-phosphoglyceraldehyde (PGAL) to 1,3-bisphosphoglycerate (BPGA) involves dehydrogenation, where NAD⁺ is reduced to NADH + H⁺. This is the only step in glycolysis that produces NADH. The other options are either later intermediates or products.
Q59. Glycolysis occurs in the:
Correct Answer: (b)
Glycolysis takes place in the cytoplasm (cytosol) of the cell, not in mitochondria or chloroplasts. All the enzymes required for the conversion of glucose to pyruvic acid are soluble and located in the cytoplasmic matrix. This allows glycolysis to proceed even in anaerobic conditions.
Q60. Match the following enzymes with their reactions:
Column-I (Enzyme)
Column-II (Reaction)
A. Hexokinase
(I) Glucose to G6P
B. Invertase
(II) Sucrose to Glucose/Fructose
C. Pyruvic dehydrogenase
(III) Pyruvate to Acetyl CoA
D. Citrate synthase
(IV) Acetyl CoA + OAA to Citric Acid
Correct Answer: (a)
Hexokinase phosphorylates glucose; invertase hydrolyses sucrose; pyruvate dehydrogenase converts pyruvate to acetyl CoA; citrate synthase forms citrate. These are standard enzyme-substrate reactions.
Q61. FADH2 is produced during the conversion of:
Correct Answer: (b)
During the TCA cycle, succinate is oxidised to fumarate by succinate dehydrogenase, which uses FAD as coenzyme, producing FADH₂. This step is part of the conversion of succinic acid to malic acid (via fumarate). The other conversions involve NAD⁺ or no reduction.
Q62. Regarding 'Respiratory Substrates': (i) Usually carbohydrates are oxidized. (ii) Proteins are used only under starvation. (iii) Pure fats are the most common substrate.
Correct Answer: (a)
Carbohydrates are the primary substrates; proteins are used under starvation; fats are not the most common—they are used when carbohydrates are depleted. Thus (i) and (ii) are correct.
Q63. Match the number of carbons in TCA intermediates:
Column-I (Acid)
Column-II (Carbon Count)
A. Citric acid
(I) 4C
B. alpha-Ketoglutaric acid
(II) 5C
C. Succinic acid
(III) 6C
D. OAA
(IV) 4C
Correct Answer: (a)
Citrate has 6 carbons; α-ketoglutarate has 5; succinate and OAA have 4. This carbon skeleton progression is key to understanding the cycle.
Q64. The RQ value for carbohydrates is:
Correct Answer: (c)
For carbohydrates like glucose, the equation C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O gives equal volumes of CO₂ and O₂ (6:6), so RQ = 1.0. Fats have RQ < 1, proteins ≈ 0.9, and organic acids may have RQ > 1.
Q65. Identify correct statements for 'Cytochrome c': (i) It is a small protein. (ii) Attached to outer surface of inner membrane. (iii) Transfers electrons from Complex III to IV.
Correct Answer: (a)
Cytochrome c is a small heme protein, loosely attached to the outer surface of the inner mitochondrial membrane, and shuttles electrons from Complex III to IV. All are correct.
Q66. Which statements about 'Amphibolic Pathway' are correct? (i) Respiration involves both breakdown and synthesis of molecules. (ii) Fatty acids enter as Acetyl CoA. (iii) Acetyl CoA can be withdrawn to synthesize fatty acids.
Correct Answer: (a)
The respiratory pathway is amphibolic: it breaks down substrates and also provides intermediates for biosynthesis. Fatty acids enter as acetyl CoA, and acetyl CoA can be used to synthesise fatty acids. All statements are correct.
Q67. Match the terms with definitions:
Column-I
Column-II
A. Obligate anaerobes
(I) Requirement for anaerobic condition is strict
B. Facultative anaerobes
(II) Can adapt to anaerobic conditions
Correct Answer: (a)
Obligate anaerobes die in oxygen; facultative anaerobes can switch between aerobic and anaerobic metabolism. These definitions are standard in microbiology.
Q68. The energy released during fermentation is ______ of the energy in glucose.
Correct Answer: (a)
Fermentation releases only a small fraction (less than 7%) of the total chemical energy stored in glucose because the end products (ethanol or lactate) still contain most of the energy. Most of the energy is trapped as ATP via substrate-level phosphorylation, but only 2 ATP per glucose are formed, representing about 7% of the potential energy.
Q69. Identify the correct statements for 'Fermentation': (i) Net gain is only two molecules of ATP per glucose. (ii) NADH is reoxidised to NAD+ in the process. (iii) Complete oxidation of glucose occurs.
Correct Answer: (a)
Fermentation yields 2 ATP net, reoxidises NADH to NAD⁺, but is incomplete oxidation—glucose is only partially broken down. Hence (i) and (ii) are correct, (iii) is false.
Q70. Which of the following phylum is being described by the given statements? (i) They are heterotrophic. (ii) They obtain food from plants directly or indirectly. (iii) They depend on the oxygen released by plants.
Correct Answer: (c)
Animals are heterotrophs that directly or indirectly depend on plants for food and oxygen. Saprophytes and fungi also obtain food from dead matter but not necessarily from plants directly, and cyanobacteria are autotrophs. Thus the description fits animals.
Q71. Assertion: F0 of ATP synthase forms a transmembrane channel.
Reason: It allows the facilitated diffusion of protons across the inner membrane.
Correct Answer: (a)
F₀ is an integral membrane protein that forms a channel for protons to move down their electrochemical gradient. This movement drives conformational changes in F₁ that synthesise ATP. The reason correctly explains the function of the channel.
Q72. Assertion: Roots, stems and leaves respire at rates far lower than animals do.
Reason: Plants have no specialized organs for gaseous exchange.
Correct Answer: (b)
Plant respiration rates are generally lower than animals because their metabolic demands are lower, not because they lack organs. The absence of specialized respiratory organs is a consequence of low metabolic needs, not the cause. Both statements are factually true but the reason does not correctly explain the assertion.
Q73. How many points in one TCA cycle result in the reduction of NAD+ to NADH + H+?
Correct Answer: (c)
In one turn of the TCA cycle, there are three dehydrogenation steps where NAD⁺ is reduced to NADH: isocitrate → α-ketoglutarate, α-ketoglutarate → succinyl-CoA, and malate → OAA. Additionally, one step reduces FAD to FADH₂ (succinate → fumarate). Thus three NADH molecules are produced.
Q74. Which of the following cannot be used as a respiratory substrate in plants?
Correct Answer: (d)
Respiratory substrates are organic compounds that can be oxidised to release energy; carbohydrates, proteins, fats and organic acids are common substrates. Pure silicon is an inorganic element and lacks the chemical bonds that can be broken for energy release. Hence it cannot serve as a respiratory substrate.
Q75. Select the correct statements about 'RQ': (i) It depends on the type of respiratory substrate. (ii) RQ for glucose is 1.0. (iii) RQ for proteins is about 0.9.
Correct Answer: (a)
RQ varies with substrate: carbohydrates = 1.0, proteins ≈ 0.9, fats ≈ 0.7. It is a direct measure of the substrate being oxidised. All statements are correct.
Q76. Identify the correct steps in 'Citric Acid Cycle': (i) Condensation of Acetyl CoA with OAA. (ii) Isomerisation of Citrate to Isocitrate. (iii) Decarboxylation to form alpha-Ketoglutaric acid.
Correct Answer: (a)
The TCA cycle begins with citrate formation, then isomerisation, then oxidative decarboxylation to α-ketoglutarate. All these steps are correct and occur in sequence.
Q77. Match the molecules with their roles in ETS:
Column-I
Column-II
A. Cytochrome c
(I) Mobile carrier between Complex III and IV
B. Ubiquinone
(II) Located within inner membrane
C. Oxygen
(III) Final hydrogen acceptor
Correct Answer: (a)
Cytochrome c shuttles electrons from Complex III to IV; ubiquinone is lipid-soluble and moves within the membrane; oxygen is the final acceptor, reduced to water.
Q78. Match the scientist with the year/contribution:
Column-I
Column-II
A. Priestley
(I) 1774 (Oxygen discovery)
B. Blackman
(II) 1905 (Limiting factors)
C. Melvin Calvin
(III) 1961 (Nobel Prize)
Correct Answer: (a)
Priestley discovered oxygen in 1774; Blackman proposed the law of limiting factors in 1905; Calvin received the Nobel Prize in 1961 for elucidating the Calvin cycle.
Q79. Regarding 'Invertase': (i) It is a digestive enzyme in animals. (ii) It converts sucrose to glucose and fructose in plants. (iii) It is used in glycolysis directly.
Correct Answer: (a)
Invertase is a plant enzyme (also found in some microorganisms) that hydrolyses sucrose; it is not an animal digestive enzyme (sucrase is the animal equivalent), and it is not part of glycolysis itself. Thus only (ii) is correct.
Q80. Assertion: Glycolysis is the only process in respiration for anaerobic organisms.
Reason: It occurs in the cytoplasm and does not require oxygen.
Correct Answer: (a)
Anaerobic organisms rely solely on glycolysis for ATP production because oxygen is absent or not used. Glycolysis is oxygen-independent and takes place in the cytoplasm, making it suitable for anaerobes. The reason correctly explains why glycolysis is the only process available.
Q81. Which are correct for 'Substrate Level Phosphorylation'? (i) Occurs in glycolysis. (ii) Occurs in Krebs cycle. (iii) Uses proton gradient and ATP synthase.
Correct Answer: (a)
Substrate-level phosphorylation happens in glycolysis and TCA cycle, where a phosphate is directly transferred to ADP/GDP. It does not involve a proton gradient or ATP synthase (that is oxidative phosphorylation). So (i) and (ii) are correct.
Q82. Match the respiratory processes with their locations:
Column-I (Process)
Column-II (Location)
A. Glycolysis
(I) Inner mitochondrial membrane
B. TCA Cycle
(II) Cytoplasm
C. ETS
(III) Mitochondrial matrix
Correct Answer: (a)
Glycolysis occurs in the cytoplasm; the TCA cycle is in the mitochondrial matrix; and the ETS is embedded in the inner mitochondrial membrane. These locations are essential for their respective biochemical steps.
Q83. Match the following for Tripalmitin RQ:
Variable
Value
A. CO2 evolved
(I) 102
B. O2 consumed
(II) 145
C. Ratio
(III) 0.7
Correct Answer: (a)
Oxidation of tripalmitin yields 102 CO₂ and consumes 145 O₂, giving RQ = 102/145 ≈ 0.7. These numbers are derived from the balanced equation.
Q84. The ratio of the volume of CO2 evolved to the volume of O2 consumed is called:
Correct Answer: (b)
The Respiratory Quotient (RQ) is defined as the ratio of CO₂ produced to O₂ consumed during respiration. It indicates the type of substrate being oxidised. Photosynthetic quotient relates to photosynthesis, transpiration ratio is about water loss, and metabolic rate is a general term.
Q85. The RQ value for tripalmitin (a fat) is:
Correct Answer: (c)
Tripalmitin (C₅₁H₉₈O₆) oxidation consumes 145 O₂ and produces 102 CO₂, giving RQ = 102/145 ≈ 0.7. This lower ratio reflects the higher oxygen demand for fat oxidation compared to carbohydrates.
Q86. Assertion: The respiratory pathway is considered amphibolic.
Reason: It involves only catabolic processes like the breakdown of glucose.
Correct Answer: (b)
The assertion is correct: the respiratory pathway is amphibolic because it participates in both breakdown (catabolism) and synthesis (anabolism) of molecules. However, the reason is false because it states only catabolic processes are involved, which contradicts the amphibolic nature. Intermediates are withdrawn for biosynthesis.
Q87. In yeast, pyruvic acid is converted to CO2 and ethanol by:
Correct Answer: (b)
In alcoholic fermentation, pyruvic acid is first decarboxylated by pyruvic acid decarboxylase to acetaldehyde, releasing CO₂. Then alcohol dehydrogenase reduces acetaldehyde to ethanol, regenerating NAD⁺. Lactate dehydrogenase produces lactic acid, hexokinase phosphorylates glucose, and citrate synthase is a TCA enzyme.
Q88. For aerobic respiration, pyruvate is transported from the cytoplasm into the:
Correct Answer: (b)
Pyruvate, produced in the cytoplasm, must enter the mitochondria for complete oxidation via the TCA cycle and oxidative phosphorylation. The mitochondria have specific transporters on their inner membrane to facilitate pyruvate uptake. The nucleus, vacuole or ribosomes are not involved in this step.
Q89. Correct features of 'Lenticels': (i) Present in bark of stems. (ii) Allow gas exchange. (iii) Help in transpiration too (though not emphasized here).
Correct Answer: (a)
Lenticels are pores in bark for gas exchange; they are not primarily for transpiration (that is the role of stomata). So (i) and (ii) are correct, (iii) is not.
Q90. Match the fermentation type with its product:
Column-I
Column-II
A. Yeast
(I) Lactic acid
B. Muscle cells
(II) Ethanol + CO2
Correct Answer: (a)
Yeast performs alcoholic fermentation producing ethanol and CO₂; muscle cells under anaerobic conditions produce lactic acid. This distinction is fundamental to understanding fermentation pathways.
Q91. Oxidation of one molecule of NADH gives rise to ______ molecules of ATP.
Correct Answer: (c)
During oxidative phosphorylation, each NADH donates electrons to Complex I, pumping protons that generate about 3 ATP molecules (based on the chemiosmotic theory). This is a standard assumption used in calculating net ATP yield. FADH₂ yields only 2 ATP because it enters at Complex II.
Q92. Respiratory pathway is better called an amphibolic pathway because it involves:
Correct Answer: (c)
Amphibolic means both catabolic and anabolic; the respiratory pathway not only breaks down substrates for energy but also provides intermediates for biosynthesis (e.g., amino acids, fatty acids). This dual role makes it amphibolic, not purely catabolic.
Q93. Assertion: Fermentation is hazardous.
Reason: Either acid or alcohol is produced.
Correct Answer: (a)
Fermentation end products like ethanol or lactic acid can be toxic when accumulated; for example, yeast cells die when ethanol reaches ~13%. The production of such compounds is indeed the reason fermentation can be hazardous, thus the reason correctly explains the assertion.
Q94. Regarding 'Cellular Respiration', which statements are correct? (i) It is the mechanism of breakdown of food materials within the cell. (ii) It traps energy for the synthesis of ATP. (iii) Breakdown of complex molecules to yield energy takes place in the cytoplasm and mitochondria.
Correct Answer: (c)
All three statements accurately describe cellular respiration: it breaks down food, traps energy as ATP, and occurs in both cytoplasm (glycolysis) and mitochondria (aerobic stages). This is the standard definition.
Q95. The net gain of ATP molecules during aerobic respiration of one molecule of glucose is assumed to be:
Correct Answer: (c)
The classic respiratory balance sheet gives a net gain of 38 ATP per glucose when considering all steps: glycolysis (2 ATP + 2 NADH → 6 ATP), pyruvate oxidation (2 NADH → 6 ATP), TCA cycle (6 NADH → 18 ATP + 2 FADH₂ → 4 ATP + 2 GTP → 2 ATP) minus 2 ATP used in glycolysis. This yields 38 ATP.
Q96. In plants, gaseous exchange occurs through:
Correct Answer: (c)
Plants lack specialised respiratory organs like lungs or gills. Instead, they exchange gases through stomata (present on leaves and young stems) and lenticels (openings in the bark of woody stems). These structures allow diffusion of O₂ and CO₂ without any active transport.
Q97. Match the intermediate and pathway entry point:
Molecule
Entry point
A. Fatty acids
(I) Acetyl CoA
B. Glycerol
(II) PGAL
C. Amino acids
(III) Pyruvate/Acetyl CoA/Krebs
Correct Answer: (a)
Fatty acids enter as acetyl CoA; glycerol enters at PGAL; amino acids can enter at pyruvate, acetyl CoA, or TCA intermediates. This reflects the amphibolic nature.
Q98. Match the cofactor type with description:
Type
Description
A. Prosthetic groups
(I) Tightly bound to apoenzyme
B. Co-enzymes
(II) Transient association
C. Metal ions
(III) Form coordination bonds
Correct Answer: (a)
Prosthetic groups are tightly bound; coenzymes are loosely associated; metal ions often form coordination bonds. This is a standard classification of cofactors.
Q99. Match the following regarding CO2 released in TCA:
Reactant to Product
CO2 released?
A. Pyruvate to Acetyl CoA
(I) Yes
B. Oxalosuccinate to alpha-KG
(II) Yes
C. alpha-KG to Succinyl CoA
(III) Yes
Correct Answer: (a)
All three steps are decarboxylation events: pyruvate dehydrogenase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase each release one CO₂. Thus all three release CO₂.
Q100. The process of incomplete oxidation of glucose under anaerobic conditions is called:
Correct Answer: (b)
Fermentation is the anaerobic breakdown of glucose where the organic substrate is only partially oxidised, yielding less energy. Aerobic respiration uses oxygen and completes oxidation via the TCA cycle and ETS. Fermentation occurs in yeast and muscle cells under oxygen debt.