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Q1. The Krebs cycle occurs in

• 1) Chloroplast
• 2) Ribosomes
• 3) Mitochondria
• 4) Cytoplasm

Solution

The Krebs cycle occurs inside the matrix of mitochondria.

Q2. Name the final hydrogen acceptor in the electron transport system. 

Solution

Oxygen 

Q3. The fermentation products of yeast are

• 1) Methyl alcohol + CO₂
• 2) Methyl alcohol + H₂O
• 3) Ethyl alcohol + CO₂
• 4) H₂O + CO₂

Solution

Yeast cells undergo alcoholic fermentation in which glucose is first converted to pyruvic acid. It is again converted to acetaldehyde. Alcohol dehydrogenase changes it to ethyl alcohol and CO₂.

Q4. Write the chemical equations for the Krebs cycle.  

Solution

Q5. State the components of complex IV. 

Solution

Cytochrome a, cytochrome a₃ and two copper centres are the components of complex IV. 

Q6. The overall goal of glycolysis, Krebs cycle and the electron transport system is the formation of

• 1) Sugars
• 2) Nucleic acids
• 3) ATP in one large oxidation reaction
• 4) ATP in small stepwise units

Solution

Glycolysis, Krebs cycle and electron transport system are meant for ATP synthesis in different steps.

Q7. The end products of aerobic respiration are

• 1) Sugar and oxygen
• 2) Water and energy
• 3) Carbon dioxide, water and energy
• 4) Carbon dioxide and energy

Solution

Aerobic respiration is an enzyme-mediated energy liberating catabolic process which involves the step-wise oxidative breakdown of organic substrate into CO₂ and water with oxygen acting as a terminal oxidant.

Q8. The respiratory quotient (RQ) for fatty acid is

• 1) 1
• 2) <1
• 3) 0
• 4) >1

Solution

In fats, a large amount of O₂ is used to combine with H₂, so the output of CO₂ is less and RQ is only 0.70.

Q9. Name the structures in plants responsible for gaseous exchange.

Solution

Stomata and lenticels

Q10. The apparatus to measure the rate of respiration and RQ is

• 1) Potometer
• 2) Respirometer
• 3) Manometer
• 4) Auxanometer

Solution

A respirometer is an instrument used to measure the rate of respiration and the respiratory quotient.

Q11. Oxidative phosphorylation involves simultaneous oxidation and phosphorylation to finally form

• 1) ATP
• 2) NADP
• 3) Pyruvate
• 4) DPN

Solution

Oxidative phosphorylation is the process in which ATP is formed as the electrons are transferred from NADH or FADH₂ to O₂ by a series of electron carriers, located in the inner membrane of the mitochondria.

Q12. When fats are the respiratory substrate, the value of RQ would be

• 1) None of the above
• 2) Approx. 0.7
• 3) Approx. 1.0
• 4) More than 1.0

Solution

When fats are the respiratory substrates, they are hydrolysed to glycerol and fatty acids. The complete oxidation of glycerol yields an RQ of approx. 0.86. As fatty acids are deficient in O₂, they require more O₂ for oxidation as compared to CO₂. Therefore, O₂ absorption is more and CO₂ liberation is less, and the RQ becomes less than 1.

Q13. The terminal cytochrome of the respiratory chain which donates electrons to oxygen is

• 1) cyt a₃
• 2) cyt c
• 3) cyt a₁
• 4) cyt b

Solution

The respiratory assembly contains electron carriers such as cytochromes. The correct sequence of electron carrier/acceptor in ATP synthesis is cyt-b, cyt-c1, cyt-c, cyt-a and cyt-a₃. Cyt-a₃ is the terminal cytochrome as it possesses two copper centres which help in the transfer of electrons to oxygen.

Q14. The site of respiration in bacteria is

• 1) Episome
• 2) Mesosome
• 3) Ribosome
• 4) Microsome

Solution

The cytoplasmic membrane of bacteria invaginates into the cytoplasm at certain places in the form of tubules called mesosomes. Enzymes found on their surfaces are associated with respiration.

Q15. In which one of the following do the two names refer to one and the same thing?

• 1) Krebs cycle and Calvin cycle
• 2) Citric acid cycle and Calvin cycle
• 3) Tricarboxylic acid cycle and urea cycle
• 4) Tricarboxylic acid cycle and citric acid cycle

Solution

The tricarboxylic acid cycle is also known as the citric acid cycle. This is an aerobic process which takes place in the matrix of mitochondria. Because it was discovered by Krebs in 1937, it is known as the Krebs cycle.

Q16. The site of glycolysis is

• 1) Mitochondrial matrix
• 2) Chloroplast
• 3) Cytoplasm
• 4) Mitochondrial inner membrane

Solution

Glycolysis is a process in which glucose is broken down to pyruvic acid without the help of an external electron acceptor such as oxygen. It occurs in the cell cytoplasm.

Q17. Give the schematic representation of the TCA cycle.  

Solution

TCA Cycle:        

Q18. State the two steps in glycolysis where ATP is used.

Solution

Step 1: When the glucose is phosphorylated into glucose-6-phosphate in the presence of hexokinase, one molecule of ATP is used. Step 2: The second molecule of ATP is used when fructose-6-phosphate is phosphorylated into fructose-1,6-bisphosphate.

Q19. Which of the following minerals activate the enzymes involved in respiration?

• 1) Sulphur and iron
• 2) Magnesium and manganese
• 3) Potassium and calcium
• 4) Nitrogen and phosphorus

Solution

Magnesium is absorbed in the form of magnesium ions (Mg²⁺). It activates the enzymes of respiration and photosynthesis. Manganese is absorbed in the form of manganous ions (Mn²⁺). It activates many enzymes which are involved in photosynthesis, respiration and nitrogen metabolism.

Q20. Respiratory Quotient (RQ) is  

• 1) CO₂/O₂  
• 2) N/C  
• 3) C/N  
• 4) O₂/CO₂  

Solution

       

Q21. In the complete oxidation of glucose, the greatest number of ATP molecules formed from ADP is during

• 1) Krebs cycle
• 2) Conversion of pyruvic acid to acetyl CoA
• 3) Glycolysis
• 4) Electron transport chain

Solution

In glycolysis, 2ATP and 2NADH₂ molecules are formed. These 2 NADH₂ molecules go to the electron transport chain.

Q22. How are fats utilised as substrates in aerobic respiration?

Solution

Fats are first broken down into glycerol and fatty acids. Fatty acids are first degraded to acetyl CoA and then they enter the TCA cycle. Glycerols are converted into phosphoglyceraldehyde, and they can then enter the glycolytic pathway.

Q23. The respiratory substrate yielding the maximum number of ATP molecules is

• 1) Glucose
• 2) Glycogen
• 3) Amylose
• 4) Ketogenic amino acid

Solution

A respiratory substrate yielding the maximum number of ATP molecules is glucose. One glucose molecule on aerobic respiration yields 36 ATP molecules.

Q24. The aerobic respiratory pathway is appropriately termed

• 1) Amphibolic
• 2) Parabolic
• 3) Anabolic
• 4) Catabolic

Solution

An amphibolic pathway is a biochemical pathway which serves both anabolic and catabolic processes. Example: Krebs cycle involves both catabolism of carbohydrates and synthesis of anabolic precursors for amino acid synthesis.

Q25. The process common to both aerobic and anaerobic organisms is  

• 1) Glycolysis  
• 2) TCA cycle  
• 3) Krebs cycle  
• 4) Glyoxylate cycle  

Solution

Glycolysis is a process in which glucose is broken down to pyruvic acid without the help of an external electron acceptor such as oxygen. It occurs in the cell cytoplasm and so is common to both aerobic and anaerobic organisms.   

Q26. Oxidative phosphorylation is the production of

• 1) ATP in photosynthesis
• 2) ATP in respiration
• 3) NADH in respiration
• 4) NADPH in photosynthesis

Solution

Oxidative phosphorylation is the synthesis of ATP from ADP and inorganic phosphate which occurs with the help of energy obtained from the oxidation of reduced coenzymes formed in cellular respiration.

Q27. The maximum amount of energy/ATP is liberated on oxidation of

• 1) Fats
• 2) Vitamins
• 3) Proteins
• 4) Starch

Solution

Fats or lipids are a source of energy. By weight, each gram mol of fat yields about 9.3 kcal of energy, i.e. more than double of that yielded by glucose.

Q28. In the Krebs cycle, FAD participates as an electron acceptor during the conversion of

• 1) Fumaric acid to malic acid
• 2) Succinic acid to fumaric acid
• 3) Succinyl CoA to succinic acid
• 4) α-Ketoglutarate to succinyl CoA

Solution

During the oxidation of succinic acid to fumaric acid, electrons and H+ ions are taken up by FAD, which gets reduced to FADH₂.

Q29. The end product of Krebs cycle is

• 1) CO₂ + H₂O
• 2) Citric acid
• 3) Lactic acid
• 4) Pyruvic acid

Solution

The Krebs cycle begins by linking acetyl CoA to oxaloacetic acid forming citric acid. In the presence of various enzymes, the cycle continues through the formation of various intermediates and the release of CO₂ and H₂O as end-products.

Q30. The end-product of oxidative phosphorylation is

• 1) ATP + H₂O
• 2) ADP
• 3) Oxygen
• 4) NADH

Solution

The aerobic breakdown of one glucose molecule yields 14 H₂O and 36 ATP molecules.

Q31. The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that ATP is formed because

• 1) ADP is pumped out of the matrix into the intermembrane space
• 2) There is a change in the permeability of the inner mitochondrial membrane towards ADP
• 3) High-energy bonds are formed in mitochondrial proteins
• 4) A proton gradient forms across the inner membrane

Solution

In 1961, Peter Mitchell put forward the chemiosmotic hypothesis for ATP synthesis.   According to this, when electrons flow from a dual proton, electron carrier to a non-hydrogen carrier, the H+ ions are released and expelled into the intermembrane space and thus creates a proton gradient with higher concentration of H+ in the intermembranous space than the matrix. Because of proton motive force, the protons flow back and the energy liberated during this backflow of protons activates ATPase present in the F₁ head to synthesise ATP.

Q32. How would proteins enter the respiratory pathway?  

Solution

Proteins are first degraded into amino acids by enzyme proteases.     The amino acids either enter the pathway immediately or first get degraded to pyruvate or acetyl CoA.  

Q33. State the factor on which the respiratory quotient depends.

Solution

The respiratory quotient depends on the type of respiratory substrate used in respiration.

Q34. The ultimate electron acceptor of respiration in aerobic organisms is

• 1) Glucose
• 2) Oxygen
• 3) Hydrogen
• 4) Cytochrome

Solution

In aerobic organisms, the final electron acceptor of respiration is oxygen. Molecular oxygen is a strong oxidising agent, and therefore, an excellent electron acceptor.

Q35. Write the chemical equation of the complete combustion of glucose during respiration.  

Solution

 

Q36. Name the enzymes which catalyse the incomplete oxidation of glucose in yeasts.  

Solution

Pyruvic acid decarboxylase and alcohol dehydrogenase  

Q37. All enzymes of the TCA cycle are located in the mitochondrial matrix except one which is located in the inner mitochondrial membrane in eukaryotes and in the cytosol in prokaryotes. This enzyme is

• 1) Isocitrate dehydrogenase
• 2) Lactate dehydrogenase
• 3) Succinate dehydrogenase
• 4) Malate dehydrogenase

Solution

Succinate dehydrogenase is present on the inner membrane of mitochondria and catalyses the oxidation of succinate to fumarate.

Q38. State the site where the oxidative decarboxylation of pyruvic acid takes place.

Solution

Matrix of mitochondrion

Q39. In the mitochondrial electron transport system, for every two pairs of electrons which pass from NADH molecules through a sequential series of cytochrome enzymes to molecular oxygen generate

• 1) 3 ATP
• 2) 4 ATP
• 3) 6 ATP
• 4) 2 ATP

Solution

In mitochondrial electron transport system, for every single pair of electrons which passes from NADH molecules through a sequential series of cytochrome enzymes to molecular oxygen generates 3 ATP. So, two pairs of electrons would generate a total of 6 ATP.

Q40. The connecting link between glycolysis and the Krebs cycle is

• 1) Acetyl CoA
• 2) Oxaloacetate
• 3) PEP
• 4) Pyruvate

Solution

In glycolysis, one molecule of glucose is broken down to two molecules of pyruvic acid. Before entering the Krebs cycle, pyruvic acid is carboxylated oxidatively to produce acetyl CoA, NADPH and CO₂ with the help of the enzyme complex pyruvate dehydrogenase. Here, acetyl CoA acts as a connecting link between glycolysis, Krebs cycle and carbohydrate and fat metabolism.

Q41. Of 38 ATP molecules produced per glucose, 32 ATP molecules are formed from NADH/FADH₂ in

• 1) Respiratory chain
• 2) EMP
• 3) Oxidative decarboxylation
• 4) Krebs cycle

Solution

Oxidative phosphorylation is the synthesis of energy-rich ATP molecules with the help of energy liberated during the oxidation of reduced coenzymes (NADH₂ and FADH₂) produced in glycolysis and the Krebs cycle. A total of 10 NADH₂ and 2FADH₂ molecules are formed in aerobic respiration. They help in the formation of 32 or 34 ATP molecules.

Q42. Protein is the respiratory substrate in

• 1) Floating respiration
• 2) Seedling state
• 3) Protoplasmic respiration
• 4) Anaerobic respiration

Solution

Respiration which uses proteins as a substrate is called protoplasmic respiration, whereas that which uses carbohydrates or fats is termed floating respiration.

Q43. Write the chemical equation for the decarboxylation of pyruvic acid to acetyl CoA.  

Solution

Q44. Name the component responsible for the transfer of electrons between complex III and complex IV.

Solution

Cytochrome c

Q45. What are respiratory substances?

Solution

Substances which are oxidised during the process of respiration are called respiratory substances.

Q46. State the site of glycolysis in the cell.

Solution

Cytoplasm

Q47. Describe the components of complex V in ETS. State their role in ATP synthesis.  

Solution

Complex V of ETS consists of an F₁ protein complex present on the peripheral membrane of mitochondria, and F₀ is an integral membrane protein complex.     F₀ forms the passage through which protons cross the inner membrane to bind to the catalytic site for the formation of ATP.     F₁ provides the active site for the binding of protons during the synthesis of ATP.  

Q48. Name the reaction during which glucose-6-phosphate is formed from glucose.

Solution

Phosphorylation

Q49. Name the component which transfers electrons from ubiquinol to cytochrome c.   

Solution

Cytochrome bc₁ or complex III transfers electrons from ubiquinol to cytochrome c.   

Q50. Name the two products formed by two successive decarboxylations in the TCA cycle.

Solution

α-ketoglutaric acid and succinyl CoA

Q51. In which form do the proteins enter the respiration pathway?

Solution

Acetyl CoA

Q52. The respiratory pathway is any amphibolic pathway. Justify.

Solution

To enter the respiratory pathway, fatty acids and proteins are broken down or degraded to acetyl CoA. During the synthesis of proteins and fats, the substances are withdrawn from the respiratory pathways and used in anabolism. The breakdown of substances is called catabolism, and the formation of substances is called anabolism. Because the respiratory pathway is responsible for both anabolism and catabolism, it is called an amphibolic pathway.

Q53. Name the enzyme which catalyses the conversion of pyruvic acid to acetyl CoA.

Solution

Pyruvic dehydrogenase

Q54. What do you understand by the term cellular respiration?

Solution

The term cellular respiration indicates the oxidation of certain macromolecules and the breaking of C-C bonds present in these molecules in the cells to release energy.

Q55. Name the enzyme which catalyses the conversion of sucrose into glucose and fructose.

Solution

Invertase

Q56. State the two products formed during glycolysis by the splitting of fructose-1,6-bisphosphate. State the relationship between NADH + H⁺.  

Solution

The splitting of fructose-1,6-bisphosphate during glycolysis forms glyceraldehydes-3-phosphate and dihydroxyacetone phosphate.     1 NADH + H⁺is equivalent to three molecules of ATP.  

Q57. Where does the electron transport system take place in the mitochondrion? 

Solution

The electron transport system takes place in the inner membrane of the mitochondrion. 

Q58. Write the chemical equation for the use of fats in respiration. Also state the RQ of the reaction.  

Solution

         

Q59. Explain ETS by giving its diagrammatic representation.   

Solution

Diagrammatic representation of ETS:        

Q60. State the two important events which occur during aerobic respiration.  

Solution

Two events which occur during aerobic respiration are      Complete oxidation of pyruvate by the removal of all hydrogen atoms, releasing three molecules of CO₂.   The electrons removed as part of hydrogen atoms are passed on to the molecular oxygen with simultaneous synthesis of ATP.  

Q61. What is the first step of the TCA cycle?

Solution

The first step of the TCA cycle is the condensation of the acetyl group of acetyl CoA with oxaloacetic acid and water to obtain citric acid.

Q62. Name the substance which is released during the formation of citric acid in the TCA cycle.

Solution

CoA

Q63. Write the other name of complex IV. 

Solution

The other name of complex IV is cytochrome c oxidase complex. 

Q64. Differentiate between fermentation and glycolysis.

Solution

Fermentation Glycolysis It occurs under anaerobic condition. It occurs during aerobic condition. The net gain of ATP is 3. The net gain of ATP is 8.  

Q65. Name the isomer of glucose-6-phosphate formed during glycolysis.  

Solution

Fructose-6-phosphate  

Q66. What will be the RQ if tripalmitin is used as a substrate in respiration?  

Solution

0.7  

Q67. Give the schematic representation of the pathway for anaerobic respiration.

Solution

Pathway of anaerobic respiration:  

Q68. State the net gain of ATPs by the oxidation of one glucose molecule.

Solution

38 ATP

Q69. Give the schematic representation of the EMP pathway (glycolysis).  

Solution

EMP Pathway:        

Q70. Draw a flowchart explaining the interrelationship between the metabolic pathway and the breakdown of different molecules into CO₂ and H₂O.

Solution

 

Q71. At a temperature above 35°C,

• 1) Rate of photosynthesis will decline earlier than that of respiration
• 2) Rate of respiration will decline earlier than that of photosynthesis
• 3) Both decline simultaneously
• 4) There is no fixed pattern

Solution

The optimum temperature for photosynthesis in C3 and C4 plants is 10-25°C and 30-45°C, respectively. However, the optimum temperature for respiration is 20-30°C which means that respiration has a higher optimum temperature than photosynthesis which declines later.

Q72. What is respiratory quotient? State the formula used to calculate the respiratory quotient.  

Solution

The respiratory quotient is the ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration.     The formula used to calculate the respiratory quotient is  

Q73. State the functions of complex I and complex II in ETS. 

Solution

Complex I oxidises the electron produced by NADH during the TCA cycle. Complex II helps in the reduction in ubiquinone to ubiquinol. 

Q74. State the net gain of ATP during glycolysis.

Solution

8 molecules of ATP

Q75. Name the pathway discovered by Gustav Embden, Otto Meyerhof and J. Parnas.

Solution

Glycolysis or EMP pathway

Q76. How many molecules of NADH + H⁺ are formed from one molecule of glucose?

Solution

Two molecules of NADH + H⁺are formed from one molecule of glucose.

Q77. Draw a well-labelled diagram indicating the synthesis of ATP in mitochondria.   

Solution

Synthesis of ATP in mitochondria: