AP Biology Chapter 9 Practice Test
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What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
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Anabolic pathways
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Catabolic pathways
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Fermentation pathways
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Thermodynamic pathways
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Bioenergetic pathways
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If you are preparing for the upcoming AP Biology exam, here we have an AP biology practice test for you. It mainly consists of chapter 9 questions and answers. This quiz tests your knowledge of cellular respiration and fermentation. Advanced Placement (AP) Biology is a biology course and exam for the students of the United States by the College Board. See moreThe below quiz will check how well prepared you are for this exam. Take the test and check your scores at the end. Good luck!
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- 2.
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
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Electron transport
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Glycolysis
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The citric acid cycle
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Oxidative phosphorylation
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Chemiosmosis
Correct Answer
A. GlycolysisExplanation
Glycolysis is the process in eukaryotic cells that breaks down glucose to produce energy in the form of ATP. It occurs in the cytoplasm and does not require oxygen. Therefore, glycolysis can proceed normally whether oxygen is present or absent. This is in contrast to processes like oxidative phosphorylation and the citric acid cycle, which require oxygen to function properly. Electron transport, oxidative phosphorylation, and chemiosmosis are all part of the aerobic respiration process that occurs in the presence of oxygen.Rate this question:
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- 3.
Which of the following occurs in the cytosol of the cell?
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Glycolysis and fermentation
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Fermentation and chemiosmosis
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Oxidation of pyruvate to acetyl CoA
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Citric acid cycle
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Oxidative phosphorylation
Correct Answer
A. Glycolysis and fermentationExplanation
Glycolysis and fermentation occur in the cytosol of the cell. Glycolysis is the process by which glucose is broken down into pyruvate, producing a small amount of ATP. Fermentation is an anaerobic process that occurs when oxygen is not present, and it converts pyruvate into either lactate or ethanol, regenerating NAD+ for glycolysis to continue. Both glycolysis and fermentation take place in the cytosol, the fluid portion of the cell outside the organelles.Rate this question:
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- 4.
Where does glycolysis takes place?
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Mitochondrial matrix
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Mitochondrial outer membrane
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Mitochondrial inner membrane
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Mitochondrial intermembrane space
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Cytosol
Correct Answer
A. CytosolExplanation
Glycolysis is the metabolic pathway that breaks down glucose to produce energy in the form of ATP. It occurs in the cytosol, which is the fluid portion of the cell outside the organelles. This is where glucose molecules are converted into pyruvate through a series of enzymatic reactions. The other options mentioned, such as the mitochondrial matrix, outer membrane, inner membrane, and intermembrane space, are not involved in glycolysis.Rate this question:
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- 5.
Which metabolic pathway is common to both fermentation and cellular respiration?
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The citric acid cycle
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The electron transport chain
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Glycolysis
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Synthesis of acetyl CoA from pyruvate
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Reduction of pyruvate to lactate
Correct Answer
A. GlycolysisExplanation
Glycolysis is the correct answer because it is a metabolic pathway that is common to both fermentation and cellular respiration. In glycolysis, glucose is broken down into pyruvate, which can then be further metabolized through either fermentation or cellular respiration. Fermentation occurs when there is no oxygen present, and pyruvate is converted into either lactate or ethanol, producing a small amount of ATP. In cellular respiration, pyruvate is transported into the mitochondria and further metabolized through the citric acid cycle and the electron transport chain, producing a large amount of ATP. Therefore, glycolysis is the metabolic pathway that links both fermentation and cellular respiration.Rate this question:
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- 6.
Which of the following normally occurs whether or not oxygen (O2) is present?
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Glycolysis
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Fermentation
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Oxidation of pyruvate to acetyl CoA
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Citric acid cycle
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Oxidative phosphorylation (chemiosmosis)
Correct Answer
A. GlycolysisExplanation
Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells and is the initial step in both aerobic and anaerobic respiration. It is the breakdown of glucose into two molecules of pyruvate. This process does not require oxygen and can occur in the presence or absence of oxygen. Therefore, glycolysis normally occurs whether or not oxygen is present.Rate this question:
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- 7.
The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question. In which step is an inorganic phosphate added to the reactant?
Correct Answer
C, AExplanation
In step C of glycolysis, an inorganic phosphate is added to the reactant. This addition of phosphate helps in the conversion of glucose-6-phosphate into fructose-1,6-bisphosphate. The phosphate group is transferred from ATP to the reactant molecule, resulting in the formation of fructose-1,6-bisphosphate, which is an important intermediate in the glycolytic pathway. This step is catalyzed by the enzyme phosphofructokinase-1. Also, in Step A, inorganic phosphate is added to glucose to form glucose-6-phosphate, so the answers are A and C.Rate this question:
- 8.
The primary role of oxygen in cellular respiration is to
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Yield energy in the form of ATP as it is passed down the respiratory chain.
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Act as an acceptor for electrons and hydrogen, forming water.
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Combine with carbon, forming CO2.
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Combine with lactate, forming pyruvate.
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Catalyze the reactions of glycolysis.
Correct Answer
A. Act as an acceptor for electrons and hydrogen, forming water.Explanation
Oxygen acts as an acceptor for electrons and hydrogen in cellular respiration, forming water. This process occurs during the electron transport chain, where electrons are transferred from one molecule to another. Oxygen is the final electron acceptor in this chain, and it combines with hydrogen ions to form water. This process is essential for the production of ATP, which is the energy currency of cells.Rate this question:
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- 9.
Which metabolic pathway is common to both cellular respiration and fermentation?
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The oxidation of pyruvate to acetyl CoA
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The citric acid cycle
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Oxidative phosphorylation
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Glycolysis
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Chemiosmosis
Correct Answer
A. GlycolysisExplanation
Glycolysis is the metabolic pathway that is common to both cellular respiration and fermentation. It is the process by which glucose is broken down into pyruvate, producing a small amount of ATP and NADH. In cellular respiration, the pyruvate produced in glycolysis is further oxidized to acetyl CoA, which enters the citric acid cycle and ultimately leads to oxidative phosphorylation and the production of a large amount of ATP. In fermentation, the pyruvate is converted into other compounds, such as lactate or ethanol, without the involvement of oxygen.Rate this question:
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- 10.
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
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It produces much less ATP than does oxidative phosphorylation.
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It is found in the cytosol, does not involve oxygen, and is present in most organisms.
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It is found in prokaryotic cells but not in eukaryotic cells.
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It relies on chemiosmosis which is a metabolic mechanism present only in the first cells-prokaryotic cells.
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It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells.
Correct Answer
A. It is found in the cytosol, does not involve oxygen, and is present in most organisms.Explanation
Glycolysis is considered to be one of the first metabolic pathways to have evolved because it is found in the cytosol, does not require oxygen, and is present in most organisms. This suggests that glycolysis is a fundamental and ancient metabolic process that was present in the earliest forms of life. Additionally, the fact that glycolysis does not rely on the presence of membrane-enclosed cell organelles found only in eukaryotic cells further supports its early evolution.Rate this question:
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- 11.
The ATP made during glycolysis is generated by
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Substrate-level phosphorylation.
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Electron transport.
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Photophosphorylation.
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Chemiosmosis.
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Oxidation of NADH to NAD+.
Correct Answer
A. Substrate-level phosphorylation.Explanation
During glycolysis, ATP is generated through substrate-level phosphorylation. This process involves the transfer of a phosphate group from a substrate molecule to ADP, forming ATP. This occurs in glycolysis when a high-energy phosphate group is transferred from a phosphorylated substrate molecule, such as glyceraldehyde-3-phosphate, to ADP, resulting in the production of ATP. This is different from electron transport, photophosphorylation, chemiosmosis, or the oxidation of NADH to NAD+, which are not directly involved in ATP production during glycolysis.Rate this question:
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- 12.
All of the following are functions of the citric acid cycle except
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Production of ATP.
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Production of NADH.
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Production of FADH2.
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Release of carbon dioxide.
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Adding electrons and protons to oxygen, forming water.
Correct Answer
A. Adding electrons and protons to oxygen, forming water.Explanation
The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is responsible for the production of ATP, NADH, and FADH2, as well as the release of carbon dioxide. However, the citric acid cycle does not directly involve the process of adding electrons and protons to oxygen to form water. This process occurs in the electron transport chain, which is the next step in cellular respiration. Therefore, the correct answer is "adding electrons and protons to oxygen, forming water."Rate this question:
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- 13.
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
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ATP, CO2and ethanol (ethyl alcohol).
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ATP, CO2, and lactate.
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ATP, NADH, and pyruvate.
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ATP, pyruvate, and oxygen.
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ATP, pyruvate, and acetyl CoA.
Correct Answer
A. ATP, CO2and ethanol (ethyl alcohol).Explanation
In the absence of oxygen, yeast cells undergo fermentation to obtain energy. This process involves the breakdown of glucose into ATP, carbon dioxide (CO2), and ethanol (ethyl alcohol). Fermentation is an anaerobic process that allows yeast cells to continue producing ATP, albeit in smaller quantities compared to aerobic respiration. The production of CO2 and ethanol are byproducts of this process. Therefore, the correct answer is ATP, CO2, and ethanol (ethyl alcohol).Rate this question:
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- 14.
The final electron acceptor of the electron transport chain that functions in oxidative phosphorylation is
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Oxygen.
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Water.
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NAD+.
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Pyruvate.
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ADP.
Correct Answer
A. Oxygen.Explanation
The final electron acceptor in the electron transport chain is oxygen. During oxidative phosphorylation, electrons are transferred through a series of protein complexes in the inner mitochondrial membrane, generating a proton gradient. This gradient is used to drive the synthesis of ATP. Oxygen acts as the final electron acceptor, combining with protons to form water. This process is essential for the efficient production of ATP in aerobic organisms.Rate this question:
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- 15.
Glycolysis is an ________ reaction.
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Exergonic
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Endothermic
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Unregulated
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Endergonic
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Abnormal
Correct Answer
A. ExergonicExplanation
Glycolysis is an exergonic reaction because it releases energy. In this process, glucose is broken down into pyruvate molecules, and during this breakdown, energy is released in the form of ATP and NADH. Exergonic reactions occur spontaneously and release energy, whereas endergonic reactions require energy input. Glycolysis is a crucial step in cellular respiration, providing energy for various cellular processes.Rate this question:
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- 16.
Which statement is not correct with regard to redox (oxidation-reduction) reactions?
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A molecule is reduced if it loses electrons.
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A molecule is oxidized if it loses electrons.
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An electron donor is called a reducing agent.
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An electron acceptor is called an oxidizing agent.
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Oxidation and reduction always go together.
Correct Answer
A. A molecule is reduced if it loses electrons.Explanation
In redox reactions, a molecule is reduced if it gains electrons, not loses electrons. Reduction involves the gain of electrons, while oxidation involves the loss of electrons. The statement that a molecule is reduced if it loses electrons is incorrect because reduction is the opposite process.Rate this question:
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- 17.
In addition to ATP, what are the end products of glycolysis?
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CO2 and H2O
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CO2 and pyruvate
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NADH and pyruvate
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CO2 and NADH
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H2O, FADH2, and citrate
Correct Answer
A. NADH and pyruvateExplanation
During glycolysis, glucose is broken down into two molecules of pyruvate. In addition to pyruvate, glycolysis also produces NADH. NADH is an energy-rich molecule that carries high-energy electrons to the electron transport chain, where it can be used to generate ATP through oxidative phosphorylation. Therefore, the correct answer is NADH and pyruvate.Rate this question:
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- 18.
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
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Glycolysis
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Fermentation
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Oxidation of pyruvate to acetyl CoA
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Citric acid cycle
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Oxidative phosphorylation (chemiosmosis)
Correct Answer
A. Oxidative phosphorylation (chemiosmosis)Explanation
Oxidative phosphorylation (chemiosmosis) produces the most ATP when glucose is completely oxidized to carbon dioxide and water. This process occurs in the mitochondria and involves the transfer of electrons from NADH and FADH2 to the electron transport chain. As the electrons move through the chain, protons are pumped across the inner mitochondrial membrane, creating an electrochemical gradient. This gradient is then used by ATP synthase to produce ATP. Overall, oxidative phosphorylation produces a large amount of ATP compared to the other options listed.Rate this question:
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- 19.
The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question. Which step consists of a phosphorylation reaction in which ATP is the phosphate source?
Correct Answer
A, aExplanation
Step A in the figure consists of a phosphorylation reaction in which ATP is the phosphate source. This can be inferred from the fact that the arrow leading into Step A is labeled with "ATP" and the arrow leading out of Step A is labeled with "ADP". This indicates that ATP is being used as a phosphate source to phosphorylate a molecule in Step A, resulting in the production of ADP.Rate this question:
- 20.
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a hydrogen ion) the molecule becomes
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Hydrogenated.
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Oxidized.
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Reduced.
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Redoxed.
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A reducing agent.
Correct Answer
A. Reduced.Explanation
When a molecule of NAD+ gains a hydrogen atom, it is accepting an electron along with the hydrogen atom. This process is known as reduction, as the molecule is gaining electrons and becoming more negatively charged. Therefore, the correct answer is "reduced."Rate this question:
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- 21.
In glycolysis, for each molecule of glucose oxidized to pyruvate
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2 molecules of ATP are used and 2 molecules of ATP are produced.
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2 molecules of ATP are used and 4 molecules of ATP are produced.
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4 molecules of ATP are used and 2 molecules of ATP are produced.
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2 molecules of ATP are used and 6 molecules of ATP are produced.
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6 molecules of ATP are used and 6 molecules of ATP are produced.
Correct Answer
A. 2 molecules of ATP are used and 4 molecules of ATP are produced.Explanation
In glycolysis, each molecule of glucose is oxidized to pyruvate. During this process, 2 molecules of ATP are used as an initial investment to activate the glucose molecule and provide energy for the subsequent steps. However, as the process continues, 4 molecules of ATP are produced through substrate-level phosphorylation. This results in a net gain of 2 molecules of ATP.Rate this question:
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- 22.
Most of the energy that enters electron transport enters as
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ATP.
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Acetyl CoA.
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Glucose.
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CO2.
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FADH2 and NADH.
Correct Answer
A. FADH2 and NADH.Explanation
The correct answer is FADH2 and NADH. During cellular respiration, glucose is broken down to produce ATP, the main energy currency of the cell. This process occurs in several stages, one of which is the electron transport chain. FADH2 and NADH, which are produced during earlier stages of cellular respiration, donate electrons to the electron transport chain. These electrons are then used to create a proton gradient, which drives the production of ATP. Therefore, FADH2 and NADH are the main sources of energy that enter the electron transport chain.Rate this question:
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- 23.
Which of the following statements describes the results of this reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
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C6H12O6 is oxidized and O2 is reduced.
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O2 is oxidized and H2O is reduced.
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CO2 is reduced and O2 is oxidized.
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C6H12O6is reduced and CO2 is oxidized.
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O2 is reduced and CO2 is oxidized.
Correct Answer
A. C6H12O6 is oxidized and O2 is reduced.Explanation
In this reaction, C6H12O6 (glucose) is being oxidized, meaning it is losing electrons and becoming a more positive ion. On the other hand, O2 (oxygen) is being reduced, meaning it is gaining electrons and becoming a more negative ion. This is consistent with the flow of electrons in a redox reaction, where one species is oxidized and another is reduced.Rate this question:
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- 24.
How many reduced dinucleotides would be produced with four turns of the citric acid cycle?
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1 FADH2 and 4 NADH
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2 FADH2 and 8 NADH
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4 FADH2 and 12 NADH
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1 FAD and 4 NAD+
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4 FAD+ and 12 NAD+
Correct Answer
A. 4 FADH2 and 12 NADHExplanation
In each turn of the citric acid cycle, 1 FADH2 and 3 NADH molecules are produced. Since there are four turns of the cycle, the total number of FADH2 molecules produced would be 4 (1 FADH2 per turn x 4 turns = 4 FADH2) and the total number of NADH molecules produced would be 12 (3 NADH per turn x 4 turns = 12 NADH). Therefore, the correct answer is 4 FADH2 and 12 NADH.Rate this question:
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- 25.
Which of the following statements about glycolysis false?
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Glycolysis has steps involving oxidation-reduction reactions.
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The enzymes of glycolysis are located in the cytosol of the cell.
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Glycolysis can operate in the complete absence of O2.
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The end products of glycolysis are CO2 and H2O.
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Glycolysis makes ATP exclusively through substrate-level phosphorylation.
Correct Answer
A. The end products of glycolysis are CO2 and H2O.Explanation
Glycolysis does not produce CO2 and H2O as end products. The end products of glycolysis are 2 molecules of pyruvate, 2 molecules of ATP, and 2 molecules of NADH. CO2 and H2O are produced during the later stages of cellular respiration, specifically in the citric acid cycle and oxidative phosphorylation.Rate this question:
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- 26.
The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation is
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Oxidation of glucose to CO2 and water.
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The thermodynamically favorable flow of electrons from NADH to the mitochondrial electron transport carriers.
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The final transfer of electrons to oxygen.
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The difference in H+ concentrations on opposite sides of the inner mitochondrial membrane.
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The thermodynamically favorable transfer of phosphate from glycolysis and the citric acid cycle intermediate molecules of ADP.
Correct Answer
A. The difference in H+ concentrations on opposite sides of the inner mitochondrial membrane.Explanation
The correct answer is the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane. During respiratory oxidative phosphorylation, the electron transport chain pumps H+ ions across the inner mitochondrial membrane, creating a concentration gradient. This gradient drives the flow of H+ ions back into the mitochondrial matrix through ATP synthase, which phosphorylates ADP to produce ATP. Therefore, the difference in H+ concentrations is the direct energy source that drives ATP synthesis.Rate this question:
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- 27.
Pyruvate is formed
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On the inner mitochondrial membrane.
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In the mitochondrial matrix.
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On the outer mitochondrial membrane.
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In the nucleus.
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In the cytosol.
Correct Answer
A. In the cytosol.Explanation
Pyruvate is formed in the cytosol.Rate this question:
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- 28.
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is
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The oxidation of glucose and other organic compounds.
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The flow of electrons down the electron transport chain.
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The affinity of oxygen for electrons.
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The H+ concentration gradient across the inner mitochondrial membrane.
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The transfer of phosphate to ADP.
Correct Answer
A. The H+ concentration gradient across the inner mitochondrial membrane.Explanation
During oxidative phosphorylation, the flow of electrons down the electron transport chain creates a proton gradient across the inner mitochondrial membrane. This proton gradient is formed by the pumping of protons from the mitochondrial matrix to the intermembrane space. ATP synthase utilizes this H+ concentration gradient to drive the synthesis of ATP. As the protons flow back into the mitochondrial matrix through ATP synthase, the energy released is used to phosphorylate ADP to ATP. Therefore, the immediate energy source that drives ATP synthesis is the H+ concentration gradient across the inner mitochondrial membrane.Rate this question:
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- 29.
Most CO2 from catabolism is released during
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Glycolysis.
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The citric acid cycle.
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Lactate fermentation.
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Electron transport.
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Oxidative phosphorylation.
Correct Answer
A. The citric acid cycle.Explanation
During catabolism, the breakdown of molecules such as glucose occurs in several stages. One of these stages is the citric acid cycle, also known as the Krebs cycle. This cycle takes place in the mitochondria and is responsible for further breaking down glucose into carbon dioxide (CO2), generating energy-rich molecules like NADH and FADH2 in the process. The CO2 produced during the citric acid cycle is then released as a waste product. Therefore, most of the CO2 from catabolism is released during the citric acid cycle.Rate this question:
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- 30.
Starting with citrate, how many of the following would be produced with three turns of the citric acid cycle?
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1 ATP, 2 CO2, 3 NADH, and 1 FADH2
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2 ATP, 2 CO2, 1 NADH, and 3 FADH2
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3 ATP, 3 CO2, 3 NADH, and 3 FADH2
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3 ATP, 6 CO2, 9 NADH, and 3 FADH2
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38 ATP, 6 CO2, 3 NADH, and 12 FADH2
Correct Answer
A. 3 ATP, 6 CO2, 9 NADH, and 3 FADH2Explanation
In each turn of the citric acid cycle, one molecule of citrate is converted to oxaloacetate. This involves the release of two molecules of CO2 and the generation of three NADH and one FADH2 molecule. Therefore, with three turns of the citric acid cycle, there will be 6 CO2 produced, along with 9 NADH and 3 FADH2 molecules. Additionally, each turn produces one molecule of GTP, which can subsequently generate one molecule of ATP through substrate-level phosphorylation, resulting in a total of 3 ATP produced.Rate this question:
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- 31.
Molecules that can potentially be converted to intermediates of glycolysis and/or the citric acid cycle include
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Amino acids and proteins.
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Glycerol and fatty acids.
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Glucose and sucrose.
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Starch and glycogen.
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All of the above
Correct Answer
A. All of the aboveExplanation
All of the given options can potentially be converted to intermediates of glycolysis and/or the citric acid cycle. Amino acids and proteins can be broken down into intermediates of these pathways through processes like transamination and deamination. Glycerol and fatty acids can be converted to acetyl-CoA, a key molecule in the citric acid cycle. Glucose and sucrose can directly enter glycolysis, while starch and glycogen can be broken down into glucose molecules that can then enter glycolysis as well. Therefore, all of the options have the potential to contribute to the intermediates of these metabolic pathways.Rate this question:
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- 32.
How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle?
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2
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5
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10
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12
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60
Correct Answer
A. 10Explanation
In each turn of the citric acid cycle, two molecules of CO2 are produced. Therefore, in five turns of the cycle, ten molecules of CO2 would be produced.Rate this question:
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- 33.
Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
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Lactate
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Glyceraldehydes-3-phosphate
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Oxaloacetate
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Acetyl CoA
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Citrate
Correct Answer
A. Acetyl CoAExplanation
Acetyl CoA is the correct answer because it is the intermediary metabolite that enters the citric acid cycle and is formed by the removal of a carbon (CO2) from one molecule of pyruvate. Acetyl CoA is produced during the process of pyruvate decarboxylation, where pyruvate loses a carbon atom in the form of CO2 and is converted into acetyl CoA. Acetyl CoA then enters the citric acid cycle to be further metabolized and produce energy.Rate this question:
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- 34.
The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question. In which reaction does an intermediate pathway become oxidized?
Correct Answer
C, cExplanation
In reaction C, an intermediate pathway becomes oxidized.Rate this question:
- 35.
The oxygen consumed during cellular respiration is involved directly in which process or event?
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Glycolysis
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Accepting electrons at the end of the electron transport chain
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The citric acid cycle
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The oxidation of pyruvate to acetyl CoA
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The phosphorylation of ADP to form ATP
Correct Answer
A. Accepting electrons at the end of the electron transport chainExplanation
During cellular respiration, oxygen is involved directly in accepting electrons at the end of the electron transport chain. This process occurs in the inner mitochondrial membrane and is the final step in the electron transport chain. Oxygen acts as the final electron acceptor, combining with electrons and protons to form water. This process is crucial for the production of ATP, as it generates a proton gradient that drives the synthesis of ATP through oxidative phosphorylation.Rate this question:
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- 36.
Starting with one molecule of glucose, the "net" products of glycolysis are
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2 NAD+, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.
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2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.
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2 FADH2, 2 pyruvate, 4 ATP, and 2 H2O.
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6 CO2, 6 H2O, 2 ATP, and 2 pyruvate.
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6 CO2, 6 H2O, 36 ATP, and 2 citrate.
Correct Answer
A. 2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.Explanation
Glycolysis is the process by which glucose is broken down into pyruvate. During glycolysis, two molecules of NADH, two molecules of H+, two molecules of pyruvate, two molecules of ATP, and two molecules of water are produced. This is the net result of glycolysis starting with one molecule of glucose. Therefore, the correct answer is 2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.Rate this question:
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- 37.
During aerobic cellular respiration, a proton gradient in mitochondria is generated by ________ and used primarily for ________.
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The electron transport chain; ATP synthesis
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The electron transport chain; substrate-level phosphorylation
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Glycolysis; production of H2O
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Fermentation; NAD+ reduction
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Diffusion of protons; ATP synthesis
Correct Answer
A. The electron transport chain; ATP synthesisExplanation
During aerobic cellular respiration, the electron transport chain plays a crucial role in generating a proton gradient in the mitochondria. This proton gradient is then used primarily for ATP synthesis. As electrons move through the electron transport chain, protons are pumped across the inner mitochondrial membrane, creating a concentration gradient. This gradient is then harnessed by ATP synthase to produce ATP, the main energy currency of the cell. Therefore, the correct answer is the electron transport chain; ATP synthesis.Rate this question:
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- 38.
The ATP made during fermentation is generated by which of the following?
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The electron transport chain
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Substrate-level phosphorylation
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Chemiosmosis
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Oxidative phosphorylation
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Aerobic respiration
Correct Answer
A. Substrate-level phosphorylationExplanation
The ATP made during fermentation is generated by substrate-level phosphorylation. This process involves the direct transfer of a phosphate group from a substrate molecule to ADP, forming ATP. Unlike oxidative phosphorylation, which occurs in the electron transport chain and requires oxygen, substrate-level phosphorylation does not require oxygen and can occur in the absence of it. Therefore, it is the main mechanism for ATP production during fermentation when oxygen is limited or not present.Rate this question:
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- 39.
How many ATP molecules are produced by glycolysis (not net)?
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1
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2
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3
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4
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5
Correct Answer
A. 4Explanation
Glycolysis is the process of breaking down glucose into pyruvate. During this process, two ATP molecules are used as an initial investment, but four ATP molecules are produced, resulting in a net gain of two ATP molecules. Therefore, the correct answer is 4.Rate this question:
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- 40.
The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question. Which step involves an endergonic reaction?
Correct Answer
AExplanation
Step A involves an endergonic reaction.Rate this question:
- 41.
In alcohol fermentation, NAD+ is regenerated from NADH during the
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Reduction of acetaldehyde to ethanol (ethyl alcohol).
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Oxidation of pyruvate to acetyl CoA.
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Reduction of pyruvate to form lactate.
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Oxidation of NAD+ in the citric acid cycle.
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Phosphorylation of ADP to form ATP.
Correct Answer
A. Reduction of acetaldehyde to ethanol (ethyl alcohol).Explanation
During alcohol fermentation, NAD+ is regenerated from NADH through the reduction of acetaldehyde to ethanol. This process involves the transfer of electrons from NADH to acetaldehyde, resulting in the conversion of acetaldehyde to ethanol and the regeneration of NAD+ in its oxidized form. This regeneration of NAD+ is crucial for glycolysis to continue producing ATP in the absence of oxygen.Rate this question:
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- 42.
Where are the proteins of the electron transport chain located?
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Cytosol
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Mitochondrial outer membrane
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Mitochondrial inner membrane
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Mitochondrial intermembrane space
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Mitochondrial matrix
Correct Answer
A. Mitochondrial inner membraneExplanation
The proteins of the electron transport chain are located in the mitochondrial inner membrane. This is where the majority of the electron transport chain complexes are embedded, allowing for the transfer of electrons and the generation of ATP. The mitochondrial inner membrane is highly folded, forming structures called cristae, which increase the surface area available for the electron transport chain proteins to carry out their functions.Rate this question:
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- 43.
The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question. Which step shows a split of one molecule into two smaller molecules?
Correct Answer
BExplanation
Step B shows a split of one molecule into two smaller molecules. In glycolysis, step B is known as the conversion of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate. This step involves the enzyme aldolase, which cleaves the fructose-1,6-bisphosphate molecule into two three-carbon molecules. These smaller molecules, glyceraldehyde-3-phosphate, then continue through the glycolysis pathway.Rate this question:
- 44.
Which of the following statements is (are) correct about an oxidation-reduction (or redox) reaction?
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The molecule that is reduced gains electrons.
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The molecule that is oxidized loses electrons.
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The molecule that is reduced loses electrons.
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The molecule that is oxidized gains electrons.
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The molecule that is reduced gains electrons and the molecule that is oxidized loses electrons.
Correct Answer
A. The molecule that is reduced gains electrons and the molecule that is oxidized loses electrons.Explanation
In an oxidation-reduction (or redox) reaction, the molecule that is reduced gains electrons, while the molecule that is oxidized loses electrons. This is because oxidation involves the loss of electrons, while reduction involves the gain of electrons. Therefore, the correct answer is that the molecule that is reduced gains electrons and the molecule that is oxidized loses electrons.Rate this question:
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- 45.
When a glucose molecule loses a hydrogen atom (not a hydrogen ion) as the result of an oxidation-reduction reaction, the molecule becomes
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Dehydrogenated.
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Hydrogenated.
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Oxidized.
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Reduced.
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An oxidizing agent.
Correct Answer
A. Oxidized.Explanation
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, it means that the glucose molecule has undergone oxidation. Oxidation is defined as the loss of electrons or an increase in the oxidation state of an atom, and in this case, the glucose molecule losing a hydrogen atom indicates that it has lost electrons and therefore has been oxidized.Rate this question:
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- 46.
What is the term used for the metabolic pathway in which glucose (C6H12O6) is degraded to carbon dioxide (CO2) and water?
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Cellular respiration
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Glycolysis
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Fermentation
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Citric acid cycle
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Oxidative phosphorylation
Correct Answer
A. Cellular respirationExplanation
Cellular respiration is the correct answer because it is the metabolic pathway in which glucose is broken down to produce carbon dioxide and water. This process occurs in the mitochondria of cells and is essential for generating energy in the form of ATP. Glycolysis is the initial step of cellular respiration, but it only partially breaks down glucose. Fermentation is an alternative pathway that occurs in the absence of oxygen, producing lactic acid or ethanol. The citric acid cycle and oxidative phosphorylation are subsequent steps in cellular respiration that further break down glucose and produce ATP.Rate this question:
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- 47.
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
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2
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4
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6
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8
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10
Correct Answer
A. 2Explanation
The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is an important part of cellular respiration and is responsible for generating energy in the form of ATP. One molecule of pyruvate, which is produced during glycolysis, enters the citric acid cycle. During the oxidation of pyruvate, each molecule loses one carbon atom in the form of carbon dioxide. Therefore, only 2 carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate.Rate this question:
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- 48.
Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
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Pyruvate
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Malate or fumarate
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Acetyl CoA
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α-ketoglutarate
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Succinyl CoA
Correct Answer
A. Acetyl CoAExplanation
The catabolic products of fatty acid breakdown, which are acetyl CoA molecules, enter into the citric acid cycle. Acetyl CoA combines with oxaloacetate to form citrate, which is the first step of the citric acid cycle. This process allows for the further breakdown of acetyl CoA and the generation of energy through the production of ATP. The other options mentioned, such as pyruvate, malate or fumarate, α-ketoglutarate, and succinyl CoA, are intermediates or products of the citric acid cycle, but acetyl CoA is the direct entry point for the catabolic products of fatty acid breakdown.Rate this question:
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- 49.
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the
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Formation of ATP.
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Reduction of NAD+.
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Restoration of the Na+/K+ balance across the membrane.
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Creation of a proton gradient.
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Lowering of pH in the mitochondrial matrix.
Correct Answer
A. Creation of a proton gradient.Explanation
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, it creates a concentration gradient of protons (hydrogen ions) across the inner membrane. This concentration gradient is known as a proton gradient. The potential energy stored in this gradient is then used by ATP synthase to produce ATP through a process called oxidative phosphorylation. Therefore, the correct answer is the creation of a proton gradient.Rate this question:
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.webp "The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question.
In which step is an inorganic phosphate added to the reactant?")
.webp "The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question.
Which step consists of a phosphorylation reaction in which ATP is the phosphate source?")
.webp "The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question.
In which reaction does an intermediate pathway become oxidized?")
.webp "The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question.
Which step involves an endergonic reaction?")
.webp "The figure below illustrates some of the steps (reactions) of glycolysis in their proper sequence. Each step is lettered. Use these letters to answer the question.
Which step shows a split of one molecule into two smaller molecules?")
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