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:
- Q: What is bioenergetics?
A: Bioenergetics is the study of energy flow and transformation within living organisms.
- Q: What is ATP?
A: ATP (adenosine triphosphate) is a high-energy molecule used as the primary energy currency in cells.
- Q: What cellular process generates ATP?
A: ATP is generated during cellular respiration through processes like glycolysis, the citric acid cycle, and oxidative phosphorylation.
- Q: Where does glycolysis occur in the cell?
A: Glycolysis occurs in the cytoplasm of the cell.
- Q: What is the net yield of ATP molecules in glycolysis?
A: The net yield of ATP molecules in glycolysis is 2 ATP molecules.
- Q: What is the end product of glycolysis?
A: The end products of glycolysis are two molecules of pyruvate.
- 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.
- Q: Where does the citric acid cycle take place in the cell?
A: The citric acid cycle takes place in the mitochondria.
- Q: What is the final electron acceptor in the electron transport chain?
A: Oxygen is the final electron acceptor in the electron transport chain.
- 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.
- 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.
- Q: What is the function of FADH2 in cellular respiration?
A: FADH2 also delivers electrons to the electron transport chain to produce ATP.
- Q: What is the main function of mitochondria in a cell?
A: Mitochondria are the sites of cellular respiration, where ATP is produced.
- 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.
- 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.
- Q: What organisms perform alcoholic fermentation?
A: Yeast and some bacteria perform alcoholic fermentation.
- Q: What is the main product of alcoholic fermentation?
A: The main products of alcoholic fermentation are ethanol and carbon dioxide.
- Q: What is the primary photosynthetic pigment in plants?
A: Chlorophyll a is the primary photosynthetic pigment in plants.
- Q: What is the purpose of photosynthesis?
A: Photosynthesis converts light energy into chemical energy (glucose) in plants and some bacteria.
- Q: Where does photosynthesis occur in plants?
A: Photosynthesis occurs in the chloroplasts of plant cells.
- Q: What is the chemical equation for photosynthesis?
A: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
- 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).
- 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.
- 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.
- Q: What is photophosphorylation?
A: Photophosphorylation is the process of generating ATP using light energy in photosynthesis.
- 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.
- 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.
- Q: What are the products of the light-dependent reactions?
A: The products of the light-dependent reactions are ATP, NADPH, and oxygen.
- Q: How is ATP synthase used in photosynthesis?
A: ATP synthase generates ATP by using the proton gradient formed during the light-dependent reactions.
- 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).
- Q: What is the Calvin cycle also known as?
A: The Calvin cycle is also known as the dark reactions or light-independent reactions.
- Q: Where does the Calvin cycle take place in the chloroplast?
A: The Calvin cycle takes place in the stroma of the chloroplast.
- Q: What molecule is initially fixed during the Calvin cycle?
A: The Calvin cycle initially fixes carbon dioxide (CO2) using the enzyme RuBisCO.
- 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).
- 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).
- 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.
- Q: How does the Calvin cycle regenerate RuBP (ribulose-1,5-bisphosphate)?
A: The last step of the Calvin cycle regenerates RuBP using ATP.
- Q: What are the products of the Calvin cycle?
A: The products of the Calvin cycle are G3P (glyceraldehyde 3-phosphate) and ADP.
- 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.
- 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.
- 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.
- Q: What is the role of carotenoids in photosynthesis?
A: Carotenoids help protect plants from excess light energy by dissipating it as heat.
- 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.
- 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.
- 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.
- Q: What are the reactants of the light-dependent reactions?
A: The reactants of the light-dependent reactions are light, water, ADP, and NADP+.
- 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.
- 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.
- Q: How does carbon dioxide enter the leaf for photosynthesis?
A: Carbon dioxide enters the leaf through stomata.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Q: Why is the citric acid cycle also called the Krebs cycle?
A: The citric acid cycle is named after its discoverer, Hans Krebs.
- 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.
- 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.
- 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.
- 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).
- 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.
- 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.
- Q: What happens during the preparatory reaction before the citric acid cycle?
A: During the preparatory reaction, pyruvate is converted into acetyl-CoA.
- Q: How many carbon atoms are in one molecule of glucose?
A: One molecule of glucose contains six carbon atoms.
- 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.
- 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.
- Q: What are the two main types of fermentation?
A: The two main types of fermentation are lactic acid fermentation and alcoholic fermentation.
- 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.
- 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.
- Q: How many molecules of NADH are produced in glycolysis?
A: Two molecules of NADH are produced in glycolysis.
- 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.
- 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.
- 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.
- 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.
- Q: What are the three phases of glycolysis?
A: The three phases of glycolysis are energy investment, cleavage, and energy generation.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Q: How does the Calvin cycle regenerate RuBP (ribulose-1,5-bisphosphate)?
A: The last step of the Calvin cycle regenerates RuBP using ATP.
- Q: What are the products of the Calvin cycle?
A: The products of the Calvin cycle are G3P (glyceraldehyde 3-phosphate) and ADP.
- 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.
- 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.
- 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.
- Q: What is the role of carotenoids in photosynthesis?
A: Carotenoids help protect plants from excess light energy by dissipating it as heat.
- 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.
- 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.
- 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.
- 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.