100 BIOENERGETICS QUESTIONS AND ANSWERS

 

The following are top 100 questions and answers in bioenergetics. Kindly note that these are concise answers that should be elaborated in tests situations:

 

1. Q: What is bioenergetics?

   A: Bioenergetics is the study of energy flow and transformation within living organisms.

 

2. Q: What is ATP?

   A: ATP (adenosine triphosphate) is a high-energy molecule used as the primary energy currency in cells.

 

3. Q: What cellular process generates ATP?

   A: ATP is generated during cellular respiration through processes like glycolysis, the citric acid cycle, and oxidative phosphorylation.

 

4. Q: Where does glycolysis occur in the cell?

   A: Glycolysis occurs in the cytoplasm of the cell.

 

5. Q: What is the net yield of ATP molecules in glycolysis?

   A: The net yield of ATP molecules in glycolysis is 2 ATP molecules.

 

6. Q: What is the end product of glycolysis?

   A: The end products of glycolysis are two molecules of pyruvate.

 

7. Q: What are the three main stages of cellular respiration?

   A: The three main stages of cellular respiration are glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation.

 

8. Q: Where does the citric acid cycle take place in the cell?

   A: The citric acid cycle takes place in the mitochondria.

 

9. Q: What is the final electron acceptor in the electron transport chain?

   A: Oxygen is the final electron acceptor in the electron transport chain.

 

10. Q: What is the purpose of the electron transport chain?

    A: The electron transport chain generates a proton gradient across the inner mitochondrial membrane, driving ATP synthesis.

 

11. Q: What is the role of NADH in cellular respiration?

    A: NADH carries high-energy electrons to the electron transport chain, where they are used to produce ATP.

 

12. Q: What is the function of FADH2 in cellular respiration?

    A: FADH2 also delivers electrons to the electron transport chain to produce ATP.

 

13. Q: What is the main function of mitochondria in a cell?

    A: Mitochondria are the sites of cellular respiration, where ATP is produced.

 

14. Q: What is the difference between aerobic and anaerobic respiration?

    A: Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses other molecules.

 

15. Q: What is lactic acid fermentation?

    A: Lactic acid fermentation is an anaerobic process that converts pyruvate into lactic acid, regenerating NAD+ for glycolysis to continue.

 

16. Q: What organisms perform alcoholic fermentation?

    A: Yeast and some bacteria perform alcoholic fermentation.

 

17. Q: What is the main product of alcoholic fermentation?

    A: The main products of alcoholic fermentation are ethanol and carbon dioxide.

 

18. Q: What is the primary photosynthetic pigment in plants?

    A: Chlorophyll a is the primary photosynthetic pigment in plants.

 

19. Q: What is the purpose of photosynthesis?

    A: Photosynthesis converts light energy into chemical energy (glucose) in plants and some bacteria.

 

20. Q: Where does photosynthesis occur in plants?

    A: Photosynthesis occurs in the chloroplasts of plant cells.

 

21. Q: What is the chemical equation for photosynthesis?

    A: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2

 

22. Q: What are the two main stages of photosynthesis?

    A: The two main stages of photosynthesis are the light-dependent reactions and the Calvin cycle (light-independent reactions).

 

23. Q: What happens during the light-dependent reactions of photosynthesis?

    A: Light-dependent reactions use light energy to produce ATP and NADPH, releasing oxygen as a byproduct.

 

24. Q: What is the role of the Calvin cycle in photosynthesis?

    A: The Calvin cycle uses ATP and NADPH to convert carbon dioxide into glucose.

 

25. Q: What is photophosphorylation?

    A: Photophosphorylation is the process of generating ATP using light energy in photosynthesis.

 

26. Q: What is the difference between C3, C4, and CAM plants?

    A: C3, C4, and CAM plants are different types of photosynthetic pathways based on how they fix carbon dioxide.

 

27. Q: What is the primary function of light-harvesting complexes in photosynthesis?

    A: Light-harvesting complexes absorb light and transfer the energy to the reaction center, where photochemistry occurs.

 

28. Q: What are the products of the light-dependent reactions?

    A: The products of the light-dependent reactions are ATP, NADPH, and oxygen.

 

29. Q: How is ATP synthase used in photosynthesis?

    A: ATP synthase generates ATP by using the proton gradient formed during the light-dependent reactions.

 

30. Q: What is the overall purpose of the light-dependent reactions?

    A: The light-dependent reactions capture and convert light energy into chemical energy (ATP and NADPH).

 

31. Q: What is the Calvin cycle also known as?

    A: The Calvin cycle is also known as the dark reactions or light-independent reactions.

 

32. Q: Where does the Calvin cycle take place in the chloroplast?

    A: The Calvin cycle takes place in the stroma of the chloroplast.

 

33. Q: What molecule is initially fixed during the Calvin cycle?

    A: The Calvin cycle initially fixes carbon dioxide (CO2) using the enzyme RuBisCO.

 

34. Q: What is the first stable product of the Calvin cycle?

    A: The first stable product of the Calvin cycle is 3-phosphoglycerate (3-PGA).

 

35. Q: What is the primary function of NADPH in the Calvin cycle?

    A: NADPH provides the reducing power to convert 3-PGA into G3P (glyceraldehyde 3-phosphate).

 

36. Q: How many turns of the Calvin cycle are needed to produce one molecule of glucose?

    A: Six turns of the Calvin cycle are needed to produce one molecule of glucose.

 

37. Q: How does the Calvin cycle regenerate RuBP (ribulose-1,5-bisphosphate)?

    A: The last step of the Calvin cycle regenerates RuBP using ATP.

 

38. Q: What are the products of the Calvin cycle?

    A: The products of the Calvin cycle are G3P (glyceraldehyde 3-phosphate) and ADP.

 

39. Q: What is the role of stomata in photosynthesis?

    A: Stomata are small pores on plant leaves that allow carbon dioxide to enter for photosynthesis while releasing oxygen and water vapor.

 

40. Q: What are the three phases of the Calvin cycle?

    A: The three phases of the Calvin cycle are carbon fixation, reduction, and regeneration of RuBP.

 

41. Q: How is the rate of photosynthesis affected by light intensity?

    A: The rate of photosynthesis increases with increasing light intensity, up to a certain point where it plateaus.

 

42. Q: What is the role of carotenoids in photosynthesis?

 

 

    A: Carotenoids help protect plants from excess light energy by dissipating it as heat.

 

43. Q: How does temperature affect photosynthesis?

    A: Photosynthesis is temperature-sensitive; it increases with temperature until it reaches an optimum point, beyond which it declines.

 

44. Q: What is the role of the photosystems in the light-dependent reactions?

    A: Photosystems are pigment-protein complexes that capture light energy and transfer it to reaction centers.

 

45. Q: What is the primary function of NADP+ in photosynthesis?

    A: NADP+ is reduced to NADPH during the light-dependent reactions, carrying energy and high-energy electrons to the Calvin cycle.

 

46. Q: What are the reactants of the light-dependent reactions?

    A: The reactants of the light-dependent reactions are light, water, ADP, and NADP+.

 

47. Q: What is photolysis in photosynthesis?

    A: Photolysis is the process of breaking down water molecules into oxygen, protons, and electrons during the light-dependent reactions.

 

48. Q: What is the role of cytochrome complex in the electron transport chain?

    A: The cytochrome complex is a protein complex in the electron transport chain that transfers electrons from cytochrome b to cytochrome c.

 

49. Q: How does carbon dioxide enter the leaf for photosynthesis?

    A: Carbon dioxide enters the leaf through stomata.

 

50. Q: How is the energy from the sun captured in photosynthesis?

    A: Energy from the sun is captured by chlorophyll and other pigments in the light-harvesting complexes.

 

51. Q: What is the relationship between photosynthesis and cellular respiration?

    A: Photosynthesis produces glucose and oxygen, which are used as reactants in cellular respiration to produce ATP and carbon dioxide.

 

52. Q: How is the energy stored in glucose released in cellular respiration?

    A: The energy stored in glucose is released through a series of redox reactions during glycolysis and the citric acid cycle.

 

53. Q: What is the purpose of the ETC (electron transport chain) in cellular respiration?

    A: The ETC generates a proton gradient that drives ATP synthesis during oxidative phosphorylation.

 

54. Q: Why is oxygen necessary for aerobic respiration?

    A: Oxygen is the final electron acceptor in the electron transport chain, allowing the efficient production of ATP.

 

55. Q: What happens to pyruvate in aerobic respiration?

    A: In aerobic respiration, pyruvate enters the mitochondria and is further oxidized in the citric acid cycle.

 

56. Q: What is the role of Coenzyme Q (CoQ) in the electron transport chain?

    A: Coenzyme Q transfers electrons from complex I and II to complex III in the electron transport chain.

 

57. Q: What is the net yield of ATP from one molecule of glucose in cellular respiration?

    A: The net yield of ATP from one molecule of glucose in cellular respiration is 36-38 ATP molecules, depending on the cell type.

 

58. Q: What is the function of the inner mitochondrial membrane in cellular respiration?

    A: The inner mitochondrial membrane houses the electron transport chain and ATP synthase, crucial for ATP production.

 

59. Q: What is the role of acetyl-CoA in the citric acid cycle?

    A: Acetyl-CoA is the starting molecule in the citric acid cycle, and it combines with oxaloacetate to form citrate.

 

60. Q: What are the electron carriers in the electron transport chain?

    A: The main electron carriers in the electron transport chain are NADH and FADH2.

 

61. Q: How is the proton gradient established during cellular respiration?

    A: The proton gradient is established by the movement of protons across the inner mitochondrial membrane during the electron transport chain.

 

62. Q: What is the role of oxygen in the electron transport chain?

    A: Oxygen is the final electron acceptor in the electron transport chain, combining with protons to form water.

 

63. Q: What is the purpose of substrate-level phosphorylation in glycolysis?

    A: Substrate-level phosphorylation generates ATP by directly transferring a phosphate group from a high-energy substrate to ADP.

 

64. Q: Why is the citric acid cycle also called the Krebs cycle?

    A: The citric acid cycle is named after its discoverer, Hans Krebs.

 

65. Q: What happens to the carbon atoms in glucose during the citric acid cycle?

    A: The carbon atoms in glucose are completely oxidized to carbon dioxide during the citric acid cycle.

 

66. Q: What is the role of the F1F0 ATP synthase complex in cellular respiration?

    A: The F1F0 ATP synthase complex produces ATP from ADP and inorganic phosphate using the proton gradient.

 

67. Q: What is the role of dehydrogenases in cellular respiration?

    A: Dehydrogenases remove hydrogen atoms from substrates, transferring them to electron carriers like NAD+ and FAD.

 

68. Q: What are the steps involved in the electron transport chain?

    A: The steps involved in the electron transport chain are: Complex I (NADH dehydrogenase), Complex II (Succinate dehydrogenase), Coenzyme Q, Complex III (Cytochrome bc1 complex), Cytochrome c, Complex IV (Cytochrome c oxidase).

 

69. Q: What is the role of the mitochondrial matrix in cellular respiration?

    A: The mitochondrial matrix houses the enzymes necessary for the citric acid cycle.

 

70. Q: What is the final product of the citric acid cycle?

    A: The final products of the citric acid cycle are ATP, NADH, FADH2, and carbon dioxide.

 

71. Q: What happens during the preparatory reaction before the citric acid cycle?

    A: During the preparatory reaction, pyruvate is converted into acetyl-CoA.

 

72. Q: How many carbon atoms are in one molecule of glucose?

    A: One molecule of glucose contains six carbon atoms.

 

73. Q: Why is the proton gradient important for ATP synthesis?

    A: The proton gradient drives the rotation of ATP synthase, enabling it to generate ATP from ADP and inorganic phosphate.

 

74. Q: What is the role of ATP synthase in cellular respiration?

    A: ATP synthase produces ATP using the energy of the proton gradient formed during the electron transport chain.

 

75. Q: What are the two main types of fermentation?

    A: The two main types of fermentation are lactic acid fermentation and alcoholic fermentation.

 

76. Q: What is the purpose of fermentation in cells?

    A: Fermentation allows the regeneration of NAD+ from NADH, ensuring that glycolysis can continue in the absence of oxygen.

 

77. Q: What type of respiration occurs in human muscle cells during intense exercise?

    A: Lactic acid fermentation occurs in human muscle cells during intense exercise when oxygen becomes limited.

 

78. Q: How many molecules of NADH are produced in glycolysis?

    A: Two molecules of NADH are produced in glycolysis.

 

79. Q: What is the function of the electron carriers in cellular respiration

 

?

    A: The electron carriers (NADH and FADH2) transport high-energy electrons to the electron transport chain.

 

80. Q: How does the electron transport chain generate a proton gradient?

    A: The electron transport chain uses energy from electron transfers to pump protons across the inner mitochondrial membrane.

 

81. Q: What is the primary role of oxygen in cellular respiration?

    A: The primary role of oxygen is to act as the final electron acceptor in the electron transport chain, forming water.

 

82. Q: What is the role of cytochrome c in the electron transport chain?

    A: Cytochrome c transfers electrons from complex III to complex IV in the electron transport chain.

 

83. Q: What are the three phases of glycolysis?

    A: The three phases of glycolysis are energy investment, cleavage, and energy generation.

 

84. Q: How is energy harvested from NADH and FADH2 in the electron transport chain?

    A: Energy from NADH and FADH2 is harvested as electrons pass through the electron transport chain, driving proton pumps.

 

85. Q: What are the three main stages of cellular respiration?

    A: The three main stages of cellular respiration are glycolysis, the citric acid cycle, and oxidative phosphorylation.

 

86. Q: What is the role of oxygen in the electron transport chain?

    A: Oxygen acts as the final electron acceptor, combining with electrons and protons to form water.

 

87. Q: What is the role of Coenzyme Q (CoQ) in the electron transport chain?

    A: Coenzyme Q transfers electrons from complex I and II to complex III in the electron transport chain.

 

88. Q: What happens to pyruvate in aerobic respiration?

    A: In aerobic respiration, pyruvate enters the mitochondria and is further oxidized in the citric acid cycle.

 

89. Q: What is the primary function of NADP+ in photosynthesis?

    A: NADP+ is reduced to NADPH during the light-dependent reactions, carrying energy and high-energy electrons to the Calvin cycle.

 

90. Q: How many turns of the Calvin cycle are needed to produce one molecule of glucose?

    A: Six turns of the Calvin cycle are needed to produce one molecule of glucose.

 

91. Q: How does the Calvin cycle regenerate RuBP (ribulose-1,5-bisphosphate)?

    A: The last step of the Calvin cycle regenerates RuBP using ATP.

 

92. Q: What are the products of the Calvin cycle?

    A: The products of the Calvin cycle are G3P (glyceraldehyde 3-phosphate) and ADP.

 

93. Q: What is the role of stomata in photosynthesis?

    A: Stomata are small pores on plant leaves that allow carbon dioxide to enter for photosynthesis while releasing oxygen and water vapor.

 

94. Q: What are the three phases of the Calvin cycle?

    A: The three phases of the Calvin cycle are carbon fixation, reduction, and regeneration of RuBP.

 

95. Q: How is the rate of photosynthesis affected by light intensity?

    A: The rate of photosynthesis increases with increasing light intensity, up to a certain point where it plateaus.

 

96. Q: What is the role of carotenoids in photosynthesis?

    A: Carotenoids help protect plants from excess light energy by dissipating it as heat.

 

97. Q: How does temperature affect photosynthesis?

    A: Photosynthesis is temperature-sensitive; it increases with temperature until it reaches an optimum point, beyond which it declines.

 

98. Q: What is the role of the photosystems in the light-dependent reactions?

    A: Photosystems are pigment-protein complexes that capture light energy and transfer it to reaction centers.

 

99. Q: What is the primary function of NADP+ in photosynthesis?

    A: NADP+ is reduced to NADPH during the light-dependent reactions, carrying energy and high-energy electrons to the Calvin cycle.

 

100. Q: How is the energy from the sun captured in photosynthesis?

     A: Energy from the sun is captured by chlorophyll and other pigments in the light-harvesting complexes.

 

   

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