Bioenergetics Test 3

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Question 1:

Which of the following compounds cannot be converted from Pyruvic acid in a single enzymatic step?





Topic: Biochemical Conversions in Cellular Metabolism

Correct Answer: D) All of the above

Detailed Hint:
  • Pyruvic acid, a key intersection in several metabolic pathways, can be converted to numerous compounds. However, this typically requires a series of enzymatic reactions.
  • Acetyl-CoA, for example, is produced from pyruvate via the pyruvate dehydrogenase complex, which involves multiple enzyme-catalyzed steps.
  • Similarly, the conversion of pyruvate to lactate and serine also involves multiple steps.
  • Therefore, the claim that any of these conversions could occur in a single step is inaccurate, making D) "All of the above" the correct answer.

Question 2:

How many net ATPs are generated during the process of glycolysis from a single glucose molecule?





Topic: Biochemical Energy Generation in Glycolysis

Correct Answer: A) 2

Detailed Hint:
  • Glycolysis is the metabolic pathway that converts glucose into pyruvate, with the simultaneous production of ATP.
  • Though four ATP molecules are produced during glycolysis, the net gain is only two ATPs since two are consumed in the early steps of the pathway.
  • Therefore, the correct answer is A, indicating a net gain of two ATPs from the glycolysis of one glucose molecule.

Question 3:

In the glycolytic process, which compound is responsible for the removal of electrons during oxidation?





Topic: Oxidation in the Glycolytic Pathway

Correct Answer: D) NAD+

Detailed Hint:
  • Glycolysis includes several steps, one of which is the oxidation of glyceraldehyde-3-phosphate.
  • During this oxidation, electrons are removed by NAD+, a coenzyme that acts as an electron acceptor.
  • This results in the reduced form of the coenzyme, NADH.
  • Therefore, the correct answer is D, "NAD+".

Question 4:

What is the quantity of CO2 produced in each iteration of the Krebs cycle?





Topic: Carbon Dioxide Production in the Krebs Cycle

Correct Answer: B) Two

Detailed Hint:
  • The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy.
  • During each turn of the cycle, two molecules of carbon dioxide are produced as byproducts.
  • Therefore, the correct answer is B, "Two".

Question 5:

What is the basis for categorizing the two types of anaerobic respiration?





Topic: Types of Anaerobic Respiration

Correct Answer: C) Both A and B

Detailed Hint:
  • Anaerobic respiration, a type of respiration occurring in the absence of oxygen, can be classified based on two factors.
  • First, it can be categorized by the type of end product formed, such as lactic acid or ethanol.
  • Second, the process by which the end product is reduced also distinguishes the types of anaerobic respiration.
  • Therefore, the correct answer is C, "Both A and B".

Question 6:

The oxidation of one acetyl-CoA molecule, resulting in the production of FADH2 and NADH, synthesizes approximately how many ATPs?





Topic: Energy Generation from Acetyl-CoA Oxidation

Correct Answer: B) 11

Detailed Hint:
  • The oxidation of one molecule of acetyl-CoA in the Krebs cycle produces 3 NADH, 1 FADH2, and 1 ATP.
  • The NADH and FADH2 molecules transport electrons to the electron transport chain, where they are used to synthesize ATP. Each NADH molecule typically generates approximately 3 ATPs, and each FADH2 molecule approximately 2 ATPs.
  • Therefore, the oxidation of one acetyl-CoA results in the net production of around 11 ATPs, making B) "11" the correct answer.

Question 7:

How many ATPs are typically produced by the oxidation of an 18 carbon atom compound?





Topic: ATP Production from Compound Oxidation

Correct Answer: C) 108

Detailed Hint:
  • Oxidation of compounds, specifically fatty acids, in cellular respiration results in the production of ATP.
  • The number of ATPs produced depends on the number of carbon atoms in the compound. For an 18-carbon atom compound, typically 108 ATPs are produced.
  • This number is calculated based on the complete breakdown and oxidation of the carbon atoms through beta-oxidation, the Krebs cycle, and the electron transport chain.
  • Therefore, the correct answer is C, "108".

Question 8:

Which substance does not result from the lactic acid fermentation process?





Topic: End Products of the Lactic Acid Fermentation

Correct Answer: D) Carbon Dioxide (2CO2)

Detailed Hint:
  • Lactic acid fermentation is an anaerobic process utilized by certain bacteria and muscle cells under low oxygen conditions.
  • The process converts glucose or glycogen into lactic acid and ATP, with the byproduct of water.
  • Carbon dioxide, however, is not a product of lactic acid fermentation, but rather of aerobic respiration.
  • Consequently, the correct answer is D, "Carbon Dioxide (2CO2)".

Question 9:

How many acetyl CoA molecules, an acetyl group attached to 'coenzyme A', are generated from one glucose molecule for involvement in the Krebs cycle?





Topic: Acetyl CoA Production

Correct Answer: D) 2

Detailed Hint:
  • The first stage of cellular respiration is glycolysis, which splits one glucose molecule into two pyruvate molecules.
  • Each pyruvate molecule then enters the mitochondria, where it is converted into acetyl CoA before entering the Krebs cycle.
  • Therefore, one glucose molecule will yield two acetyl CoA molecules, making D) "2" the correct answer.

Question 10:

Upon oxidation of glucose, the energy released is stored in which form?





Topic: Energy Storage During Glucose Oxidation

Correct Answer: C) ATP

Detailed Hint:
  • The main objective of glucose oxidation during cellular respiration is to convert the stored chemical energy within the glucose molecule into a more usable form: ATP.
  • The process of glucose oxidation involves several stages, including glycolysis, the Krebs cycle, and the electron transport chain, all of which contribute to ATP production.
  • Therefore, the correct answer is C, "ATP".

Question 11:

Which molecule typically captures the excited electrons from Photosystem II during photosynthesis?





Topic: Electron Capture in Photosynthesis

Correct Answer: B) Plastoquinone (PQ)

Detailed Hint:
  • Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis.
  • It works by seizing electrons from water molecules, exciting them, and then transferring these excited electrons to the primary electron acceptor, Plastoquinone (PQ).
  • Therefore, the correct answer is B, "Plastoquinone (PQ)".

Question 12:

The process of glucose synthesis during photosynthesis requires how many ATP and NADPH2 molecules?





Topic: Energy Consumption in Photosynthesis

Correct Answer: B) 18 ATP, 12 NADPH2

Detailed Hint:
  • The dark reaction of photosynthesis, also known as the Calvin cycle, is responsible for glucose synthesis.
  • In a single dark reaction, it takes 9 ATP and 6 NADPH2 molecules to produce half a glucose molecule. Hence, to synthesize 1 complete glucose molecule, two dark reactions are necessary.
  • This implies that 18 ATP and 12 NADPH2 molecules are required in total, making B) "18 ATP, 12 NADPH2" the correct answer.

Question 13:

Which term is used to describe the reaction when 3-Phosphoglycerate (PGA) is converted into Glyceraldehyde 3-phosphate (PGAL) during photosynthesis?





Topic: Reaction Stages in Photosynthesis

Correct Answer: B) Reduction

Detailed Hint:
  • The second phase of the dark reaction in photosynthesis involves the conversion of 3-Phosphoglycerate (PGA) into Glyceraldehyde 3-phosphate (PGAL).
  • This conversion process is a reduction reaction, as it involves the addition of electrons or hydrogen to PGA.
  • Therefore, the correct term for this reaction is B) "Reduction".

Question 14:

In a eukaryotic cell, where does the Krebs cycle primarily take place?





Topic: Cellular Location of the Krebs Cycle

Correct Answer: D) Mitochondria

Detailed Hint:
  • The Krebs cycle, also known as the citric acid cycle, is an integral part of cellular respiration in eukaryotes.
  • This series of enzyme-catalyzed chemical reactions occurs within the matrix of the mitochondria, the powerhouses of the cell.
  • Therefore, the correct answer is D, "Mitochondria".

Question 15:

The enzyme RUBISCO is present in which types of plants?





Topic: Presence of RUBISCO in Plants

Correct Answer: C) Both C3 and C4 plants

Detailed Hint:
  • RUBISCO is a key enzyme involved in the first step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants into energy-rich molecules like glucose.
  • Both C3 and C4 plants use RUBISCO for carbon fixation, showing subtle differences in the way they capture and process carbon dioxide.
  • Consequently, the correct answer is C, "Both C3 and C4 plants".

Question 16:

Which among the following enzyme complexes is not involved in the Electron Transport Chain (ETC)?





Topic: Enzymes in the Electron Transport Chain

Correct Answer: D) Ligase

Detailed Hint:
  • The Electron Transport Chain (ETC) is a series of protein complexes embedded in the inner mitochondrial membrane that shuttle electrons during the redox reactions that release energy used to generate ATP.
  • These complexes include the NADH dehydrogenase complex, the cytochrome b/c complex, and the cytochrome oxidase complex.
  • Ligase, however, is not part of the ETC. It is an enzyme that facilitates the joining of DNA strands together.
  • Therefore, the correct answer is D, "Ligase".

MCQ 17:

What is the total ATP yield from a single glucose molecule during the Krebs cycle in a eukaryotic cell?





Topic: ATP Production in the Krebs Cycle

Correct Answer: D) 24 ATP

Detailed Hint:
  • The Krebs cycle, also known as the citric acid cycle, is the second stage of cellular respiration.
  • Although the direct yield from the Krebs cycle is only 2 ATP, the cycle also produces NADH and FADH2. These molecules provide the electrons for the Electron Transport Chain (ETC) which generates most of the ATP.
  • When considering the ATP produced by NADH and FADH2 via the ETC, the total yield from one round of the Krebs cycle from a glucose molecule is 24 ATP (2 ATP directly from the Krebs cycle, 18 ATP from NADH, and 4 ATP from FADH2). Hence, D) "24 ATP" is the correct answer.

MCQ 18:

In anaerobic respiration, what is the net amount of oxidative ATP produced?





Topic: ATP Generation in Anaerobic Respiration

Correct Answer: D) No oxidative ATP produced

Detailed Hint:
  • Anaerobic respiration is a type of respiration that does not use oxygen. It's a way for organisms to produce energy in low-oxygen environments.
  • In this process, the Electron Transport Chain (ETC), where oxidative phosphorylation occurs, does not work due to the absence of oxygen. Hence, there is no oxidative production of ATP.
  • Glycolysis, which precedes the ETC, does indeed produce some ATP, but it is not through oxidative mechanisms. Therefore, the correct answer is D, "No oxidative ATP produced".

Question 19:

During alcoholic fermentation, how many molecules of carbon dioxide are released from one molecule of glucose?





Topic: CO2 Production in Alcoholic Fermentation

Correct Answer: B) 2 CO2 molecules

Detailed Hint:
  • Alcoholic fermentation is a type of anaerobic process where glucose (or other sugars) are converted into cellular energy and produce ethanol and carbon dioxide as by-products.
  • In the first step of this process, one glucose molecule is converted into two pyruvate molecules, releasing two molecules of CO2.
  • Therefore, the correct answer is B, "2 CO2 molecules".

Question 20:

What is the end product of the light-dependent reactions of photosynthesis?





Topic: Light-dependent Reactions of Photosynthesis

Correct Answer: D) All of the above

Detailed Hint:
  • The process of photosynthesis in plants involves two main stages: the light-dependent reactions and the light-independent reactions.
  • The light-dependent reactions occur in the thylakoid membranes of the chloroplasts, wherein light energy is converted into chemical energy as ATP and NADPH. Oxygen is also produced as a by-product during these reactions.
  • Therefore, the correct answer is D, "All of the above".

Question 21:

What is an essential requirement for the light-dependent stage of photosynthesis to occur?





Topic: Requirements of the Light-dependent Stage of Photosynthesis

Correct Answer: B) Water (H2O)

Detailed Hint:
  • The light-dependent reactions of photosynthesis are the first stage of this process and rely on light energy and water.
  • Water is split in the process of photolysis to release electrons, hydrogen ions, and oxygen. The electrons and hydrogen ions are used to generate ATP and NADPH, while oxygen is released as a by-product.
  • Hence, the correct answer is B, "Water (H2O)".

Question 22:

How many NADPH2 are produced in each cyclic electron transport chain during photosynthesis?





Topic: NADPH Production in Photosynthesis

Correct Answer: D) None

Detailed Hint:
  • Photosynthesis includes two types of electron transport chains: cyclic and non-cyclic. The cyclic electron transport only involves Photosystem I and generates ATP but not NADPH.
  • NADPH, along with ATP, are produced during non-cyclic electron transport, which involves both Photosystem I and II.
  • Therefore, the correct answer is D, "None".

Question 23:

What is the final product of the glycolysis process in yeast?





Topic: Glycolysis End product in Yeast

Correct Answer: A) Ethanol and Carbon Dioxide

Detailed Hint:
  • Glycolysis is the metabolic pathway that converts glucose into pyruvate.
  • In the yeast species Saccharomyces cerevisiae, the pyruvate produced by glycolysis undergoes fermentation to produce ethanol and carbon dioxide as by-products.
  • Therefore, the correct answer is A, "Ethanol and Carbon Dioxide".

Question 24:

Which photosystem(s) participate(s) in the cyclic electron transport chain?





Topic: Participants in Cyclic Electron Transport Chain

Correct Answer: A) Only Photosystem-I (PS-I)

Detailed Hint:
  • Photosynthesis involves two types of electron transport chains - cyclic and non-cyclic.
  • In the cyclic electron transport, only Photosystem I is involved and the major purpose is to generate ATP. No NADPH is produced in this cycle.
  • Hence, the correct answer is A, "Only Photosystem-I (PS-I)".

Question 25:

What is the process called during the light reaction that results in ATP synthesis?





Topic: ATP Synthesis in Light Reaction

Correct Answer: A) Photophosphorylation

Detailed Hints:
  • In photosynthesis, the synthesis of ATP in the light-dependent reactions is driven by light, a process known as photophosphorylation.
  • Photophosphorylation uses the energy in photons of light to create a high-energy electron donor and an electron acceptor.
  • Electron transport between donor and acceptor leads to proton pumping and ATP formation. Hence, the correct answer is A, "Photophosphorylation".

Question 26:

How many gross ATP molecules are generated from a single glucose molecule?





Topic: ATP Generation from Glucose

Correct Answer: D) Both B and C

Detailed Hints:
  • The process of cellular respiration converts glucose into ATP, with various stages including glycolysis, the Krebs cycle, and oxidative phosphorylation.
  • ATP yield per glucose molecule can be up to 36 or 38, depending on the efficiency of the organism's electron transport system.
  • Therefore, the correct answer is D, "Both B and C".

Question 27:

In non-cyclic photophosphorylation;





Topic: Non-cyclic Photophosphorylation

Correct Answer: D) All the above

Detailed Hints:
  • Non-cyclic photophosphorylation involves both photosystem I and II, and it leads to the formation of ATP, NADPH, and O2.
  • The electron flow in this process is unidirectional, from water to NADP+.
  • Therefore, the correct answer is D, "All the above".

Question 28:

In the C3 pathway, the first stable compound formed is;





Topic: C3 Pathway

Correct Answer: C) PGA

Detailed Hints:
  • In photosynthesis, the Calvin cycle or C3 pathway, generates a three-carbon compound, 3-phosphoglycerate (PGA), as the first stable product.
  • PGA is then converted into glyceraldehyde 3-phosphate (PGAL), not the first, but a crucial intermediate in the pathway.
  • Therefore, the correct answer is C, "PGA".

Question 29:

Which molecule enters the mitochondria following the process of glycolysis?





Topic: Glycolysis and Mitochondria

Correct Answer: D) Acetyl CoA

Detailed Hints:
  • Glycolysis, which takes place in the cytosol, breaks down glucose into two molecules of pyruvate.
  • Each pyruvate molecule is then converted into Acetyl CoA, which enters the mitochondria for the next stage of cellular respiration, the Krebs cycle.
  • Hence, the correct answer is D, "Acetyl CoA".

Question 30:

How many molecules of FADH2 are produced in each Electron Transport Chain (ETC)?





Topic: Electron Transport Chain

Correct Answer: D) None

Detailed Hints:
  • The Electron Transport Chain (ETC) is the final component of aerobic respiration and is the only part of glucose metabolism that uses atmospheric oxygen.
  • It is important to note that FADH2 is produced in the Krebs cycle and then used in the ETC, but no FADH2 is produced within the ETC itself.
  • Therefore, the correct answer is D, "None".

Question 31:

How many NADPH molecules are needed for the metabolism of a single glucose molecule?





Topic: Glucose Metabolism

Correct Answer: C) 12

Detailed Hints:
  • Glucose metabolism involves the processes of glycolysis, the Krebs cycle, and the electron transport chain.
  • During these processes, NADPH is generated and used in the reactions. Specifically, one glucose molecule requires 12 NADPH molecules for its metabolism.
  • Thus, the correct answer is C, "12".

Question 32:

What does the stroma of the chloroplast facilitate the fixation of?





Topic: Chloroplast Stroma

Correct Answer: D) Carbon Dioxide

Detailed Hints:
  • The stroma is the dense fluid within the chloroplast and is involved in the synthesis of organic molecules from water and carbon dioxide.
  • Specifically, it is the site of the dark reactions of photosynthesis, where carbon dioxide is incorporated, or "fixed" into carbohydrate molecules.
  • Hence, the correct answer is D, "Carbon Dioxide".

Question 33:

During the dark phase of photosynthesis, which compound is oxidized and which is reduced?





Topic: Dark Phase of Photosynthesis

Correct Answer: D) NADPH2 and CO2

Detailed Hint:
  • The dark phase of photosynthesis, also known as the Calvin Cycle, involves the conversion of carbon dioxide and other compounds into glucose.
  • In this process, NADPH2 (or NADPH) gets oxidized to NADP+ and CO2 is reduced to form glucose.
  • Therefore, the correct answer is D, "NADPH2 and CO2".

Question 34:

Where does the Electron Transport Chain (ETC) occur?





Topic: Electron Transport Chain (ETC)

Correct Answer: C) Inner membrane of mitochondria

Detailed Hint:
  • The ETC is one of the stages of cellular respiration, and it occurs in the mitochondria, the powerhouses of the cell.
  • More specifically, the ETC takes place in the inner mitochondrial membrane where it uses high-energy electrons from NADH and FADH2 to pump hydrogen ions across the membrane.
  • Thus, the correct answer is C, "Inner membrane of mitochondria".

Question 35:

How many ATP molecules can be produced from a single glucose molecule, including those generated through substrate-level and oxidative phosphorylation in the direct pathway?





Topic: ATP Production

Correct Answer: C) 38

Detailed Hint:
  • During the process of glucose metabolism, ATP molecules are generated in two distinct ways - substrate-level phosphorylation and oxidative phosphorylation.
  • In substrate-level phosphorylation, a phosphate group is directly transferred from a donor molecule to ADP, producing ATP. This takes place during glycolysis and the Krebs cycle, resulting in a total of 4 ATPs.
  • Oxidative phosphorylation, which occurs in the electron transport chain, uses the energy released by the oxidation of nutrients to produce ATP. This process can produce up to 34 ATPs from one glucose molecule.
  • Therefore, adding the ATPs produced in both processes, the total comes to 38 ATPs (Answer C).

Question 36:

In which type of plants can Calvin's cycle be found?





Topic: Photosynthesis

Correct Answer: D) All photosynthetic plants

Detailed Hint:
  • Calvin's cycle, also known as the dark reaction or the light-independent reaction, is a crucial stage of photosynthesis where carbon dioxide is converted to glucose.
  • This cycle is not limited to a certain type of plant but is a common pathway in all photosynthetic plants, including C3, C4, and CAM plants.
  • Therefore, irrespective of the plant type, if it is photosynthetic, Calvin's cycle will occur in its chloroplasts. Hence, the correct answer is D, "All photosynthetic plants".

Question 37:

Where does the proton gradient develop within the mitochondria?





Topic: Mitochondrial Proton Gradient

Correct Answer: B) Inner membrane

Detailed Hint:
  • A proton gradient is essential for the process of oxidative phosphorylation in the mitochondria. It is established in the inner mitochondrial membrane due to the electron transport chain activity.
  • The electron transport chain pumps hydrogen ions (protons) across the inner membrane into the intermembrane space, creating a region of high proton concentration.
  • This gradient is utilized by ATP synthase to generate ATP from ADP and inorganic phosphate. Hence, the correct answer is B, "Inner membrane".

Question 38:

Which compound produces the most energy during aerobic respiration?





Topic: Energy Production in Aerobic Respiration

Correct Answer: B) Triglycerides

Detailed Hint:
  • Aerobic respiration involves the breakdown of different compounds - glucose, triglycerides (fats), proteins, and sucrose to generate energy.
  • While all these compounds can yield energy, triglycerides produce more than twice the energy compared to carbohydrates and proteins.
  • This is because the carbon atoms in triglycerides are highly reduced, meaning they have more potential to yield energy when oxidized. Hence, the correct answer is B, "Triglycerides".

Question 39:

How many net ATP molecules are generated from a single glucose molecule during oxidative phosphorylation?





Topic: Oxidative Phosphorylation

Correct Answer: D) Both A and C

Detailed Hint:
  • Oxidative phosphorylation is a part of cellular respiration where ATP is formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers.
  • The total number of ATP molecules produced can vary. This is because the number of ATP molecules produced per molecule of NADH or FADH2 is not fixed but ranges from 1.5 to 2.5 for NADH and from 1 to 1.5 for FADH2.
  • Hence, oxidative phosphorylation can produce either 34 ATP (direct pathway) or 32 ATP (indirect pathway) from a single glucose molecule. Thus, the correct answer is D, "Both A and C".

Question 40:

What is the nature of the reactions involved in glycolysis?





Topic: Glycolysis

Correct Answer: C) Both

Detailed Hint:
  • Glycolysis is a metabolic pathway that breaks down glucose into pyruvate, generating energy in the form of ATP and NADH.
  • The reactions involved in glycolysis can be both reversible and irreversible. Some steps in the pathway are equilibrium reactions, capable of proceeding in either direction (reversible), while others are driven to completion by a large negative free energy change (irreversible).
  • Therefore, the correct answer is C, "Both".

MCQ 41:

What is the total ATP yield from the complete oxidation of Pyruvate?





Topic: ATP Formation from Pyruvate Oxidation

Correct Answer: D) 15

Detailed Hint:
  • Pyruvate, the end product of glycolysis, undergoes complete oxidation in the mitochondria, providing a substantial yield of ATP.
  • During its oxidation, one pyruvic acid molecule generates 4 NADH, 1 FADH2, and 1 ATP.
  • By oxidative phosphorylation, 4 NADH produce 12 ATP (4*3), 1 FADH2 produces 2 ATP, and the directly formed ATP adds one more.
  • Summing up, the total ATP yield from the complete oxidation of one pyruvic acid molecule is 15 ATP.
  • Hence, the correct answer is D, "15".

MCQ 42:

Which vitamin forms a part of the Coenzyme A structure?





Topic: Coenzyme A Composition

Correct Answer: B) Vitamin B1

Detailed Hint:
  • Coenzyme A, an essential cofactor in various metabolic reactions, includes a nucleotide and a vitamin portion in its structure.
  • Specifically, the vitamin portion of Coenzyme A is derived from Vitamin B1, making Vitamin B1 an essential nutrient for energy metabolism.
  • Thus, the correct answer to the question is B, "Vitamin B1".

MCQ 43:

During the dark reaction, where do the three carbon atoms of 3-PGA originate from?





Topic: Carbon Source in Dark Reaction

Correct Answer: C) RuBP + CO2

Detailed Hint:
  • The dark reaction, or Calvin cycle, is a set of light-independent reactions during photosynthesis that convert CO2 into glucose.
  • The three carbon atoms of 3-PGA, a molecule formed in the Calvin cycle, are derived from both RuBP (Ribulose biphosphate) and CO2.
  • Therefore, the correct answer is C, "RuBP + CO2".

MCQ 44:

Where are the electron carriers of the chloroplast located?





Topic: Electron Carriers in Chloroplast

Correct Answer: D) Within its thylakoid membrane

Detailed Hint:
  • The chloroplast houses the essential machinery for photosynthesis in plants.
  • Electron carriers, integral components of the photosynthetic process, are principally located within the thylakoid membrane of the chloroplast.
  • The thylakoid membrane is the site of the light-dependent reactions of photosynthesis, where electron transfer takes place.
  • Hence, the correct answer is D, "Within its thylakoid membrane".

MCQ 45:

What are the products of the light-dependent reaction in photosynthesis?





Topic: Products of Light-Dependent Reaction

Correct Answer: C) NADPH + ATP

Detailed Hint:
  • The light-dependent reactions are the initial stages of photosynthesis, taking place in the thylakoid membranes of the chloroplasts.
  • These reactions use light energy to produce two key molecules: ATP (adenosine triphosphate), the energy currency of cells, and NADPH (nicotinamide adenine dinucleotide phosphate), a reducing agent involved in the synthesis of organic molecules in the subsequent light-independent reactions.
  • Therefore, the correct answer is C, "NADPH + ATP".

MCQ 46:

Where are most enzymes involved in the Krebs cycle located?





Topic: Krebs Cycle Enzyme Location

Correct Answer: D) Mitochondrial matrix

Detailed Hint:
  • The Krebs cycle, also known as the citric acid cycle, is a key component of cellular respiration.
  • It is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.
  • Most enzymes involved in the Krebs cycle are located in the mitochondrial matrix, the fluid that fills the inside of the mitochondria, where these biochemical processes take place.
  • Therefore, the correct answer is D, "Mitochondrial matrix".

MCQ 47:

What is the total number of Electron Transport Chains (ETC) that occur after the breakdown of one glucose molecule?





Topic: Electron Transport Chain Frequency

Correct Answer: D) 12

Detailed Hint:
  • The electron transport chain (ETC) is the final component of aerobic respiration and is the only part directly using oxygen.
  • In the process of glucose metabolism, each glucose molecule is split into two pyruvate molecules during glycolysis.
  • Each pyruvate is then oxidized to acetyl CoA and enters the Krebs cycle.
  • Each turn of the Krebs cycle produces one FADH2 and three NADH molecules, each of which can donate electrons to the ETC.
  • Because glucose metabolism involves two turns of the Krebs cycle, the total number of ETCs after the breakdown of one glucose molecule is 12.
  • Hence, the correct answer is D, "12".

Question 48:

Which molecule serves as the final electron acceptor in the Electron Transport Chain (ETC)?





Topic: Final Electron Acceptor in ETC

Correct Answer: B) Oxygen

Detailed Hint:
  • The electron transport chain (ETC) is a series of proteins in the inner mitochondrial membrane involved in a high-energy electron transfer process.
  • During this process, electrons are passed from one carrier to another, releasing energy that is used to form ATP.
  • The final electron acceptor of the ETC is oxygen, which combines with free protons and electrons to form water.
  • Therefore, the correct answer is B, "Oxygen".

MCQ 49:

How many NADH molecules are generated from one glucose molecule during aerobic respiration?





Topic: NADH Production in Aerobic Respiration

Correct Answer: C) 10

Detailed Hint:
  • In aerobic respiration, one glucose molecule is metabolized to produce energy.
  • During this metabolic process, NADH, a high-energy electron carrier, is generated at two stages: during glycolysis and the Krebs cycle.
  • In total, one glucose molecule generates two NADH molecules in glycolysis, two in the conversion of pyruvate to acetyl CoA, and six in the Krebs cycle, totaling ten NADH molecules.
  • Therefore, the correct answer to the question is C, "10".

MCQ 50:

What is the end product of the fermentation process when sugars are metabolized?





Topic: Fermentation End Products

Correct Answer: D) All of the above

Detailed Hint:
  • Fermentation is a metabolic process that breaks down complex organic molecules, such as sugars, into simpler substances.
  • Different types of fermentation processes yield different end products. For example, lactic acid fermentation produces acids, alcoholic fermentation produces alcohol and gases (carbon dioxide), and other fermentation processes can produce a combination of these products.
  • Therefore, when sugars are metabolized in the process of fermentation, the end products could potentially be acids, gases, alcohol, or a combination of these. Hence, the correct answer is D, "All of the above".
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