Cellular Energetics Practice Quiz

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  • 1/93 Questions

    What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

    • Anabolic pathways
    • Catabolic pathways
    • Fermentation pathways
    • Thermodynamic pathways
    • Bioenergetic pathways
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About This Quiz

Quiz over AP Biology Unit 3: Cellular Energetics (Cell Respiration and Photosynthesis)

Cellular Energetics Practice Quiz - Quiz

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  • 2. 

    What is the term used for the metabolic pathway in which glucose (C6H12O6) is degraded to carbon dioxide (CO2) and water?

    • Cellular respiration

    • Glycolysis

    • Fermentation

    • Citric acid cycle

    • Oxidative phosphorylation

    Correct Answer
    A. Cellular respiration
    Explanation
    Cellular respiration is the correct answer because it refers to the metabolic pathway in which glucose is broken down into carbon dioxide and water. This process occurs in the mitochondria of cells and is important for the production of ATP, the energy currency of the cell. Glycolysis, fermentation, citric acid cycle, and oxidative phosphorylation are all components or stages of cellular respiration.

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  • 3. 

    Which of the following statements correctly describe(s) catabolic pathways?

    • They do not depend on enzymes.

    • They consume energy to build up polymers from monomers.

    • They release energy as they degrade polymers to monomers.

    • They lead to the synthesis of catabolic compounds.

    • Both A and B

    Correct Answer
    A. They release energy as they degrade polymers to monomers.
    Explanation
    Catabolic pathways involve the breakdown of larger molecules into smaller ones, such as polymers being broken down into monomers. This process releases energy, which is a characteristic feature of catabolic pathways. The statement that they do not depend on enzymes is incorrect, as enzymes are essential for catalyzing the reactions involved in catabolism. The statement that they consume energy to build up polymers from monomers is also incorrect, as this is a characteristic of anabolic pathways, which are the opposite of catabolic pathways. Therefore, the correct statement is that catabolic pathways release energy as they degrade polymers to monomers.

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  • 4. 

    Which of the following statements describes the results of this reaction? C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + Energy

    • C6H12O6 is oxidized and O2 is reduced.

    • O2 is oxidized and H2O is reduced.

    • CO2 is reduced and O2 is oxidized.

    • C6H12O6 is reduced and CO2 is oxidized.

    • O2 is reduced and CO2 is oxidized.

    Correct Answer
    A. C6H12O6 is oxidized and O2 is reduced.
    Explanation
    In this reaction, glucose (C6H12O6) is oxidized, meaning it loses electrons, while oxygen (O2) is reduced, meaning it gains electrons. This is evident from the fact that glucose is converted into carbon dioxide (CO2) and water (H2O), and oxygen is converted into water. The production of energy also indicates that a redox reaction is occurring, as the transfer of electrons releases energy. Therefore, the correct answer is that C6H12O6 is oxidized and O2 is reduced.

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  • 5. 

    Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

    • Entropy.

    • Activation energy.

    • Endothermic level.

    • Heat content.

    • Free-energy content.

    Correct Answer
    A. Activation energy.
    Explanation
    In a chemical reaction, reactants need to overcome a thermodynamic barrier called activation energy in order to form products. Activation energy refers to the minimum amount of energy required for a reaction to occur. It acts as a barrier that reactant molecules must surpass in order to reach the transition state and proceed with the reaction. Once the activation energy is surpassed, the reaction can proceed spontaneously and products can be formed. Therefore, activation energy is the correct answer in this case.

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  • 6. 

    In addition to ATP, what are the end products of glycolysis?

    • CO2 and H2O

    • CO2 and pyruvate

    • NADH and pyruvate

    • CO2 and NADH

    • H2O, FADH2, and citrate

    Correct Answer
    A. NADH and pyruvate
    Explanation
    During glycolysis, glucose is broken down into two molecules of pyruvate. This process also produces NADH, which is an energy carrier molecule. Therefore, the end products of glycolysis are NADH and pyruvate.

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  • 7. 

    Which statement is not correct with regard to redox (oxidation-reduction) reactions?

    • A molecule is reduced if it loses electrons.

    • A molecule is oxidized if it loses electrons.

    • An electron donor is called a reducing agent.

    • An electron acceptor is called an oxidizing agent.

    • 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 addition of electrons to a molecule, which leads to a decrease in its oxidation state. On the other hand, oxidation occurs when a molecule loses electrons, resulting in an increase in its oxidation state. Therefore, the statement "A molecule is reduced if it loses electrons" is not correct in the context of redox reactions.

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  • 8. 

    Which of the following statements is true concerning catabolic pathways?

    • They combine molecules into more energy-rich molecules.

    • They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.

    • They are endergonic.

    • They are spontaneous and do not need enzyme catalysis.

    • They build up complex molecules such as protein from simpler compounds.

    Correct Answer
    A. They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.
    Explanation
    Catabolic pathways involve the breakdown of complex molecules into simpler ones, releasing energy in the process. This energy is often used to fuel anabolic pathways, which build complex molecules from simpler ones. Therefore, catabolic pathways are usually coupled with anabolic pathways, supplying energy in the form of ATP.

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  • 9. 

    Which of the following occurs in the cytosol of the cell?

    • Glycolysis and fermentation

    • Fermentation and chemiosmosis

    • Oxidation of pyruvate to acetyl CoA

    • Citric acid cycle

    • Oxidative phosphorylation

    Correct Answer
    A. Glycolysis and fermentation
    Explanation
    Glycolysis and fermentation occur in the cytosol of the cell. Glycolysis is the process in which glucose is broken down into pyruvate, and it takes place in the cytosol. Fermentation is an anaerobic process that occurs after glycolysis, where pyruvate is converted into either lactic acid or ethanol, depending on the organism. Both glycolysis and fermentation are essential for the production of ATP in the absence of oxygen.

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  • 10. 

    The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction

    • Gains electrons and gains energy.

    • Loses electrons and loses energy.

    • Gains electrons and loses energy.

    • Loses electrons and gains energy.

    • Neither gains nor loses electrons, but gains or loses energy.

    Correct Answer
    A. Loses electrons and loses energy.
    Explanation
    In a redox or oxidation-reduction reaction, the reducing agent is the molecule that donates electrons. When a molecule donates electrons, it loses them, resulting in a loss of energy. Therefore, the correct answer is "loses electrons and loses energy."

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  • 11. 

    What is a nonprotein "helper" of an enzyme molecule called?

    • Accessory enzyme

    • Allosteric group

    • Coenzyme

    • Functional group

    • Enzyme activator

    Correct Answer
    A. Coenzyme
    Explanation
    A nonprotein "helper" of an enzyme molecule is called a coenzyme. Coenzymes are small organic molecules that aid in the catalytic function of enzymes. They bind to the enzyme and assist in the transfer of chemical groups or electrons during the enzymatic reaction. Coenzymes are often derived from vitamins and are essential for the proper functioning of many enzymes in the body.

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  • 12. 

    What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?

    • Feedback regulationfeedback regulation

    • Bioenergetics

    • Energy coupling

    • Entropy

    • Cooperativity

    Correct Answer
    A. Energy coupling
    Explanation
    Energy coupling is the term used to describe the transfer of free energy from catabolic pathways (which break down molecules to release energy) to anabolic pathways (which build molecules using energy). This process allows the energy released from catabolism to be used for the synthesis of complex molecules in anabolic reactions. Energy coupling is essential for maintaining the energy balance in cells and ensuring that the energy released from one reaction is efficiently utilized in another reaction.

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  • 13. 

    Organisms that can exist with light as an energy source and an inorganic form of carbon and other raw materials

    • Are called photoautotrophs.

    • Do not exist in nature.

    • Are called heterotrophs.

    • Are best classified as decomposers.

    • Both C and D

    Correct Answer
    A. Are called photoautotrophs.
    Explanation
    Photoautotrophs are organisms that can use light as an energy source and inorganic forms of carbon and other raw materials to carry out photosynthesis and produce their own organic compounds. They are able to convert sunlight into chemical energy, which is used to fuel their metabolic processes. This ability allows them to be self-sufficient and not rely on other organisms for their energy needs. Therefore, the correct answer is that organisms with these characteristics are called photoautotrophs.

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  • 14. 

    Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

    • Catalysis

    • Metabolism

    • Anabolism

    • Dehydration

    • Catabolism

    Correct Answer
    A. Catabolism
    Explanation
    Catabolism is the correct answer because it refers to the cellular process of breaking down large molecules into smaller ones. This process involves the release of energy and the breakdown of complex molecules such as proteins, carbohydrates, and fats into simpler molecules that can be used for energy production or other cellular functions.

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  • 15. 

    When a glucose molecule loses a hydrogen atom (not a hydrogen ion) as the result of an oxidation-reduction reaction, the molecule becomes

    • Dehydrogenated.

    • Hydrogenated.

    • Oxidized.

    • Reduced.

    • 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 the loss of electrons or an increase in the oxidation state of an atom or molecule. In this case, the glucose molecule loses a hydrogen atom, which means it has lost an electron. Therefore, the correct answer is oxidized.

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  • 16. 

    ATP generally energizes a cellular process by

    • Releasing heat upon hydrolysis.

    • Acting as a catalyst.

    • Coupling free energy released by ATP hydrolysis to free energy needed by other reactions.

    • Breaking a high-energy bond.

    • Binding directly to the substrate(s) of the enzyme.

    Correct Answer
    A. Coupling free energy released by ATP hydrolysis to free energy needed by other reactions.
    Explanation
    ATP is a molecule that stores and transfers energy within cells. It does so by undergoing hydrolysis, where a phosphate group is cleaved from ATP, releasing energy. This energy is then used to power other cellular reactions that require energy. Therefore, the correct answer states that ATP couples the free energy released during its hydrolysis to the free energy needed by other reactions, effectively transferring and providing energy for cellular processes.

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  • 17. 

    How can one increase the rate of a chemical reaction?

    • Increase the activation energy needed.

    • Cool the reactants.

    • Decrease the concentration of the reactants.

    • Add a catalyst.

    • Increase the entropy of the reactants.

    Correct Answer
    A. Add a catalyst.
    Explanation
    Adding a catalyst can increase the rate of a chemical reaction by providing an alternative pathway with a lower activation energy. A catalyst is a substance that increases the rate of a reaction without being consumed in the process. It works by providing an alternative reaction pathway that has a lower activation energy, allowing more reactant molecules to have sufficient energy to undergo the reaction. This lowers the energy barrier for the reaction, enabling it to proceed at a faster rate. Therefore, adding a catalyst can effectively increase the rate of a chemical reaction.

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  • 18. 

    An enzyme catalyzes a reaction by

    • Supplying the energy to speed up a reaction.

    • Lowering the energy of activation of a reaction.

    • Lowering the G of a reaction.

    • Changing the equilibrium of a spontaneous reaction.

    • Increasing the amount of free energy of a reaction.

    Correct Answer
    A. Lowering the energy of activation of a reaction.
    Explanation
    Enzymes are biological catalysts that speed up chemical reactions in cells. They achieve this by lowering the energy of activation, which is the energy required to start a reaction. By lowering this energy barrier, enzymes enable the reactant molecules to reach the transition state more easily, increasing the reaction rate. Enzymes do not supply energy to the reaction or change the equilibrium or amount of free energy of a reaction. Therefore, the correct answer is "lowering the energy of activation of a reaction."

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  • 19. 

      The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the free energy for the reduction of NAD+ to NADH is +53 kcal/mole. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?

    • Most of the free energy available from the oxidation of glucose is used in the production of ATP in glycolysis.

    • Glycolysis is a very inefficient reaction, with much of the energy of glucose released as heat.

    • Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.

    • There is no CO2 or water produced as products of glycolysis.

    • Glycolysis consists of many enzymatic reactions, each of which extracts some energy from the glucose molecule.

    Correct Answer
    A. Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.
    Explanation
    During glycolysis, glucose is partially oxidized to form two molecules of pyruvate. This oxidation releases a small amount of free energy, which is used to produce ATP. However, the majority of the free energy available from the oxidation of glucose remains in pyruvate. This is why only two molecules of NADH are formed during glycolysis, even though it seems like more could be formed. The remaining free energy in pyruvate can be further extracted through other metabolic pathways, such as the citric acid cycle, to produce additional NADH and ATP.

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  • 20. 

    How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?

    • 2

    • 4

    • 6

    • 8

    • 10

    Correct Answer
    A. 2
    Explanation
    During the citric acid cycle, one molecule of pyruvate is oxidized to produce one molecule of acetyl-CoA. Acetyl-CoA enters the citric acid cycle by combining with a four-carbon molecule, oxaloacetate, to form a six-carbon molecule, citrate. As the cycle progresses, citrate is gradually oxidized and decarboxylated, resulting in the release of two carbon dioxide molecules. Therefore, the oxidation of one molecule of pyruvate leads to the entry of two carbon atoms into the citric acid cycle.

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  • 21. 

    How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle?

    • 2

    • 5

    • 10

    • 12

    • 60

    Correct Answer
    A. 10
    Explanation
    The citric acid cycle produces 2 molecules of carbon dioxide (CO2) per turn. Since there are 5 turns of the cycle, the total number of CO2 molecules produced would be 2 x 5 = 10.

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  • 22. 

    Where does the Calvin cycle take place?

    • Stroma of the chloroplast

    • Thylakoid membrane

    • Cytoplasm surrounding the chloroplast

    • Chlorophyll molecule

    • Outer membrane of the chloroplast

    Correct Answer
    A. Stroma of the chloroplast
    Explanation
    The Calvin cycle takes place in the stroma of the chloroplast. The stroma is the fluid-filled space surrounding the thylakoid membranes, where the light-independent reactions of photosynthesis occur. In the Calvin cycle, carbon dioxide is converted into glucose using the energy from ATP and NADPH produced during the light-dependent reactions. The enzymes and other necessary components for this process are located in the stroma, making it the correct answer.

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  • 23. 

    Which of the following statements is (are) correct about an oxidation-reduction (or redox) reaction?

    • The molecule that is reduced gains electrons.

    • The molecule that is oxidized loses electrons.

    • The molecule that is reduced loses electrons.

    • The molecule that is oxidized gains electrons.

    • Both A and B are correct.

    Correct Answer
    A. Both A and B are correct.
    Explanation
    In an oxidation-reduction (redox) reaction, one molecule is oxidized and another is reduced. The molecule that is reduced gains electrons, which causes a decrease in its oxidation state. On the other hand, the molecule that is oxidized loses electrons, resulting in an increase in its oxidation state. Therefore, both statements A and B are correct.

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  • 24. 

    Which of the following statements about NAD+ is false?

    • NAD+ is reduced to NADH during both glycolysis and the citric acid cycle.

    • NAD+ has more chemical energy than NADH.

    • NAD+ is reduced by the action of dehydrogenases.

    • NAD+ can receive electrons for use in oxidative phosphorylation.

    • In the absence of NAD+, glycolysis cannot function.

    Correct Answer
    A. NAD+ has more chemical energy than NADH.
    Explanation
    NAD+ is actually the oxidized form of NADH, meaning it has less chemical energy. During glycolysis and the citric acid cycle, NAD+ is reduced to NADH by accepting electrons. NAD+ is reduced by dehydrogenases, and it can transfer the electrons it receives to the electron transport chain for oxidative phosphorylation. In the absence of NAD+, glycolysis cannot proceed, as NAD+ is required as an electron acceptor. Therefore, the statement "NAD+ has more chemical energy than NADH" is false.

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  • 25. 

    The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as

    • Metabolic inhibition.metabolic inhibition.

    • Feedback inhibition.

    • Allosteric inhibition.

    • Noncooperative inhibition.

    • Reversible inhibition.

    Correct Answer
    A. Feedback inhibition.
    Explanation
    Feedback inhibition is the mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway. This process helps regulate the production of the end product, preventing an excessive accumulation. When the concentration of the end product reaches a certain level, it binds to an enzyme involved in an earlier step, causing a conformational change that inhibits the enzyme's activity. This negative feedback loop helps maintain homeostasis and balance in metabolic pathways.

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  • 26. 

    How does a non-competitive inhibitor decrease the rate of an enzyme reaction?

    • By binding at the active site of the enzyme

    • By changing the structure of the enzyme

    • By changing the free energy change of the reaction

    • By acting as a coenzyme for the reaction

    • By decreasing the activation energy of the reaction

    Correct Answer
    A. By changing the structure of the enzyme
    Explanation
    A non-competitive inhibitor decreases the rate of an enzyme reaction by changing the structure of the enzyme. This means that the inhibitor binds to a site on the enzyme that is not the active site, causing a change in the enzyme's shape. This change in structure prevents the enzyme from properly binding to the substrate and carrying out the reaction efficiently, ultimately slowing down the rate of the reaction.

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  • 27. 

    Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?

    • Pyruvate

    • Malate or fumarate

    • Acetyl CoA

    • Alpha-ketoglutarate

    • Succinyl CoA

    Correct Answer
    A. Acetyl CoA
    Explanation
    The catabolic products of fatty acid breakdown enter into the citric acid cycle through acetyl CoA. Acetyl CoA is derived from the breakdown of fatty acids and serves as the starting point for the citric acid cycle. It combines with oxaloacetate to form citrate, initiating the cycle. Acetyl CoA is an important intermediate in energy metabolism and plays a crucial role in the oxidation of fatty acids for energy production.

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  • 28. 

    When glucose (C6H12O6) is oxidized to CO2 and water in cellular respiration, approximately 40% of the energy content of glucose is transferred to

    • The citric acid cycle.

    • Glycolysis.

    • ATP (adenosine triphosphate).

    • Heat.

    • Oxygen (O2).

    Correct Answer
    A. ATP (adenosine triphosphate).
    Explanation
    During cellular respiration, glucose is broken down into CO2 and water. This process occurs in multiple stages, with the citric acid cycle and glycolysis being two of them. However, the majority of the energy released from glucose is transferred to ATP. ATP is the primary energy currency of cells, and it provides the energy needed for various cellular processes. Therefore, the correct answer is ATP.

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  • 29. 

    Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

    • The covalent bonds in organic molecules are higher energy bonds than those in water and carbon dioxide.

    • Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).

    • The oxidation of organic compounds can be used to make ATP.

    • The electrons have a higher potential energy when associated with water and CO2 than they do in organic compounds.

    • The covalent bond in O2 is unstable and easily broken by electrons from organic molecules.

    Correct Answer
    A. Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).
    Explanation
    The movement of electrons from atoms with a lower affinity for electrons to atoms with a higher affinity for electrons releases energy. This is because the transfer of electrons allows the atoms to achieve a more stable and energetically favorable state. In the case of the oxidation of organic compounds, the carbon atoms, which have a lower affinity for electrons, transfer their electrons to oxygen atoms, which have a higher affinity for electrons. This transfer of electrons releases energy, making the oxidation process exergonic.

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  • 30. 

    Where does glycolysis takes place?

    • Mitochondrial matrix

    • Mitochondrial outer membrane

    • Mitochondrial inner membrane

    • Mitochondrial intermembrane space

    • Cytosol

    Correct Answer
    A. Cytosol
    Explanation
    Glycolysis is a metabolic pathway that occurs in the cytosol of cells. It is the first step in cellular respiration and involves the breakdown of glucose into pyruvate. The cytosol is the fluid portion of the cytoplasm, where many cellular processes take place. Therefore, glycolysis occurs in the cytosol.

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  • 31. 

    A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

    • The starch solution has less free energy than the sugar solution.

    • The hydrolysis of starch to sugar is endergonic.

    • The activation energy barrier for this reaction cannot be surmounted.

    • Starch cannot be hydrolyzed in the presence of so much water.

    • Starch hydrolysis is nonspontaneous.

    Correct Answer
    A. The activation energy barrier for this reaction cannot be surmounted.
    Explanation
    The correct answer is "the activation energy barrier for this reaction cannot be surmounted." This means that the energy required to break the bonds in starch and convert it into simple sugars is too high to occur at room temperature. Therefore, the starch solution does not readily decompose into a solution of simple sugars.

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  • 32. 

    Where are the proteins of the electron transport chain located?

    • Cytosol

    • Mitochondrial outer membrane

    • Mitochondrial inner membrane

    • Mitochondrial intermembrane space

    • Mitochondrial matrix

    Correct Answer
    A. Mitochondrial inner membrane
    Explanation
    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 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.

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  • 33. 

    During aerobic cellular respiration, a proton gradient in mitochondria is generated by ____ and used primarily for ____.

    • The electron transport chain; ATP synthesis

    • The electron transport chain; substrate-level phosphorylation

    • Glycolysis; production of H2O

    • Fermentation; NAD+ reduction

    • Diffusion of protons; ATP synthesis

    Correct Answer
    A. The electron transport chain; ATP synthesis
    Explanation
    During aerobic cellular respiration, the electron transport chain plays a crucial role in generating a proton gradient in mitochondria. This process involves the transfer of electrons through a series of protein complexes, which results in the pumping of protons across the inner mitochondrial membrane. The accumulation of protons on one side of the membrane creates a proton gradient. This proton gradient is then utilized by ATP synthase, an enzyme embedded in the membrane, to generate ATP through a process called chemiosmosis. Therefore, the correct answer is "the electron transport chain; ATP synthesis."

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  • 34. 

    The ATP made during fermentation is generated by which of the following?

    • The electron transport chain

    • Substrate-level phosphorylation

    • Chemiosmosis

    • Oxidative phosphorylation

    • Aerobic respiration

    Correct Answer
    A. Substrate-level phosphorylation
    Explanation
    Substrate-level phosphorylation is the process by which ATP is directly synthesized from a phosphorylated substrate molecule during glycolysis and the citric acid cycle. This occurs when a high-energy phosphate group is transferred from a substrate molecule to ADP, forming ATP. In contrast, oxidative phosphorylation, which occurs in the electron transport chain and chemiosmosis, involves the transfer of electrons and the generation of a proton gradient to drive ATP synthesis. Fermentation does not involve the electron transport chain or oxidative phosphorylation, making substrate-level phosphorylation the correct answer.

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  • 35. 

    Which of the following is not true concerning the cellular compartmentation of the steps of respiration or fermentation?

    • Acetyl CoA is produced only in the mitochondria.

    • Lactate is produced only in the cytosol.

    • NADH is produced only in the mitochondria.

    • FADH2 is produced only in the mitochondria.

    • ATP is produced in the cytosol and the mitochondria.

    Correct Answer
    A. NADH is produced only in the mitochondria.
    Explanation
    NADH is not produced only in the mitochondria. NADH is produced in both the cytosol and the mitochondria. In the cytosol, NADH is produced during glycolysis, which is the first step of both respiration and fermentation. In the mitochondria, NADH is produced during the citric acid cycle and the electron transport chain, which are the subsequent steps of respiration. Therefore, NADH is produced in both cellular compartments during the process of respiration or fermentation.

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  • 36. 

    All of the events listed below occur in the light reactions of photosynthesis except

    • Oxygen is produced.

    • NADP+ is reduced to NADPH.

    • Carbon dioxide is incorporated into PGA.

    • ADP is phosphorylated to yield ATP.

    • Light is absorbed and funneled to reaction-center chlorophyll a.

    Correct Answer
    A. Carbon dioxide is incorporated into PGA.
    Explanation
    In the light reactions of photosynthesis, oxygen is produced as a byproduct of splitting water molecules. NADP+ is reduced to NADPH, which is an electron carrier that carries high-energy electrons to the Calvin cycle. ADP is phosphorylated to yield ATP, which is the main energy currency of cells. Light is absorbed and funneled to reaction-center chlorophyll a, which is the first step in capturing light energy. However, carbon dioxide is not incorporated into PGA (phosphoglycerate), a three-carbon compound that is formed during the Calvin cycle. Instead, carbon dioxide is incorporated into a five-carbon compound called RuBP (ribulose bisphosphate) in the Calvin cycle.

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  • 37. 

    During glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is

    • Transferred to ADP, forming ATP.

    • Transferred directly to ATP.

    • Retained in the pyruvate.

    • Stored in the NADH produced.

    • Used to phosphorylate fructose to form fructose-6-phosphate.

    Correct Answer
    A. Retained in the pyruvate.
    Explanation
    During glycolysis, glucose is broken down into pyruvate. This process involves the transfer of energy from glucose to various molecules. However, most of the energy from glucose is retained in the pyruvate molecules. This is because glycolysis is an anaerobic process, meaning it does not require oxygen. As a result, the pyruvate molecules produced during glycolysis still contain a significant amount of energy that can be further utilized in other metabolic pathways, such as the citric acid cycle and oxidative phosphorylation, to produce more ATP.

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  • 38. 
    During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the G for the new reaction? - ProProfs

    During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the G for the new reaction?

    • -40 kcal/mol

    • -20 kcal/mol

    • 0 kcal/mol

    • +20 kcal/mol

    • +40 kcal/mol

    Correct Answer
    A. -20 kcal/mol
    Explanation
    When the amount of enzyme in a reaction is doubled, it does not affect the value of G, which represents the change in free energy. Therefore, the G for the new reaction will still be -20 kcal/mol.

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  • 39. 

    Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

    • Glycolysis and the oxidation of pyruvate to acetyl CoA

    • Oxidation of pyruvate to acetyl CoA and the citric acid cycle

    • The citric acid cycle and oxidative phosphorylation

    • Oxidative phosphorylation and fermentation

    • Fermentation and glycolysis

    Correct Answer
    A. Oxidation of pyruvate to acetyl CoA and the citric acid cycle
    Explanation
    During the oxidation of pyruvate to acetyl CoA and the citric acid cycle stages of cellular respiration, carbon dioxide (CO2) is released. In the oxidation of pyruvate to acetyl CoA, pyruvate molecules are converted into acetyl CoA, releasing one molecule of CO2 in the process. In the citric acid cycle, acetyl CoA enters a series of reactions that ultimately produce energy and release two more molecules of CO2. Therefore, the correct answer is the oxidation of pyruvate to acetyl CoA and the citric acid cycle.

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  • 40. 

    The primary function of the mitochondrion is the production of ATP. To carry out this function, the mitochondrion must have all of the following except

    • The membrane-bound electron transport chain carrier molecules.

    • Proton pumps embedded in the inner mitochondrial membrane.

    • Enzymes for glycolysis.

    • Enzymes for the citric acid cycle.

    • Mitochondrial ATP synthase.

    Correct Answer
    A. Enzymes for glycolysis.
    Explanation
    The primary function of the mitochondrion is the production of ATP through cellular respiration. This process involves the membrane-bound electron transport chain carrier molecules, proton pumps embedded in the inner mitochondrial membrane, enzymes for the citric acid cycle, and mitochondrial ATP synthase. However, glycolysis, which is the initial step in the breakdown of glucose to produce ATP, occurs in the cytoplasm outside of the mitochondrion. Therefore, enzymes for glycolysis are not required within the mitochondrion for ATP production.

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  • 41. 

    Each time a molecule of glucose (C6H12O6) is completely oxidized via aerobic respiration, how many oxygen molecules (O2). are required?

    • 1

    • 2

    • 6

    • 12

    • 38

    Correct Answer
    A. 6
    Explanation
    When a molecule of glucose is completely oxidized via aerobic respiration, it undergoes a series of reactions that result in the production of carbon dioxide (CO2) and water (H2O). The balanced equation for this process is 6O2 + C6H12O6 -> 6CO2 + 6H2O. From the equation, it can be seen that 6 molecules of oxygen are required for the complete oxidation of one molecule of glucose.

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  • 42. 

    In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of

    • ATP, CO2and ethanol (ethyl alcohol).

    • ATP, CO2, and lactate.

    • ATP, NADH, and pyruvate.

    • ATP, pyruvate, and oxygen.

    • ATP, pyruvate, and acetyl CoA.

    Correct Answer
    A. ATP, CO2and ethanol (ethyl alcohol).
    Explanation
    In the absence of oxygen, yeast cells undergo fermentation to produce energy. This process involves the breakdown of glucose into ATP, carbon dioxide (CO2), and ethanol (ethyl alcohol). This allows the yeast cells to generate ATP, which is the energy currency of the cell, along with the byproducts CO2 and ethanol. This explanation aligns with the given correct answer: ATP, CO2, and ethanol.

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  • 43. 

    Which of the following describe(s) some aspect of metabolism?

    • Synthesis of macromoleculessynthesis of macromolecules

    • Breakdown of macromolecules

    • Control of enzyme activity

    • A and B only

    • A, B, and C

    Correct Answer
    A. A, B, and C
    Explanation
    The correct answer is A, B, and C. This is because metabolism involves the synthesis of macromolecules, the breakdown of macromolecules, and the control of enzyme activity. These processes are essential for the functioning and regulation of cells and organisms.

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  • 44. 

    Starting with citrate, how many of the following would be produced with three turns of the citric acid cycle?

    • 1 ATP, 2 CO2, 3 NADH, and 1 FADH2

    • 2 ATP, 2 CO2, 1 NADH, and 3 FADH2

    • 3 ATP, 3 CO2, 3 NADH, and 3 FADH2

    • 3 ATP, 6 CO2, 9 NADH, and 3 FADH2

    • 38 ATP, 6 CO2, 3 NADH, and 12 FADH2

    Correct Answer
    A. 3 ATP, 6 CO2, 9 NADH, and 3 FADH2
    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 an important part of cellular respiration, which produces energy in the form of ATP. Each turn of the citric acid cycle produces 1 ATP, 2 CO2, 3 NADH, and 1 FADH2. Therefore, with three turns of the cycle, the correct answer is 3 ATP, 6 CO2, 9 NADH, and 3 FADH2.

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  • 45. 

    What is the primary function of the light reactions of photosynthesis?

    • To produce energy-rich glucose from carbon dioxide and water

    • To produce ATP and NADPH

    • To produce NADPH used in respiration

    • To convert light energy to the chemical energy of PGAL

    • To use ATP to make glucose

    Correct Answer
    A. To produce ATP and NADPH
    Explanation
    The primary function of the light reactions of photosynthesis is to produce ATP and NADPH. These two molecules are essential for the subsequent dark reactions of photosynthesis, where they provide the energy and reducing power needed to convert carbon dioxide into glucose. ATP is a high-energy molecule that serves as the primary energy currency of the cell, while NADPH is a reducing agent that provides the necessary electrons for the synthesis of glucose. Therefore, the production of ATP and NADPH in the light reactions is crucial for the overall process of photosynthesis.

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  • 46. 

    In order for NAD+ to remove electrons from glucose or other organic molecules, which of the following must be true?

    • The organic molecule or glucose must be negatively charged in order to reduce the positively charged NAD+.

    • Oxygen must be present to oxidize the NADH produced back to NAD+.

    • The free energy liberated when electrons are removed from the organic molecules must be greater than the energy required to give the electrons to NAD+.

    • A and B are both correct.

    • A, B, and C are all correct.

    Correct Answer
    A. The free energy liberated when electrons are removed from the organic molecules must be greater than the energy required to give the electrons to NAD+.
    Explanation
    For NAD+ to remove electrons from glucose or other organic molecules, the free energy released during this process must be greater than the energy required to transfer the electrons to NAD+. This ensures that the reaction is thermodynamically favorable and can proceed spontaneously. A negative charge on the organic molecule or glucose is not necessary for this process, and the presence of oxygen is not directly related to the removal of electrons from the organic molecules. Therefore, options A and B are incorrect, and the correct answer is C.

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  • 47. 

    Which metabolic process is most closely associated with intracellular membranes?

    • Substrate-level phosphorylation

    • Oxidative phosphorylation

    • Glycolysis

    • The citric acid cycle

    • Alcohol fermentation

    Correct Answer
    A. Oxidative phosphorylation
    Explanation
    Oxidative phosphorylation is the metabolic process that is most closely associated with intracellular membranes. This process occurs in the inner mitochondrial membrane and involves the transfer of electrons through a series of protein complexes, creating a proton gradient. This gradient is then used by ATP synthase, which is embedded in the membrane, to produce ATP. Therefore, oxidative phosphorylation relies on the presence of intracellular membranes for its functioning.

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  • 48. 

    Which of the following normally occurs whether or not oxygen (O2) is present?

    • Glycolysis

    • Fermentation

    • Oxidation of pyruvate to acetyl CoA

    • Citric acid cycle

    • Oxidative phosphorylation (chemiosmosis)

    Correct Answer
    A. Glycolysis
    Explanation
    Glycolysis is the metabolic pathway that occurs in the cytoplasm of cells and is the first step in both aerobic and anaerobic respiration. It is the process of breaking down glucose into pyruvate, producing a small amount of ATP and NADH. While the subsequent steps of cellular respiration (such as fermentation, oxidation of pyruvate to acetyl CoA, citric acid cycle, and oxidative phosphorylation) require oxygen, glycolysis can occur in the absence of oxygen. Therefore, glycolysis is the only process listed that normally occurs whether or not oxygen is present.

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  • 49. 

      Which of the following statements concerning the metabolic degradation of glucose (C6H12O6) to carbon dioxide (CO2) and water is (are) true?

    • The breakdown of glucose to carbon dioxide and water is exergonic.

    • The breakdown of glucose to carbon dioxide and water has a free energy change of -686 kcal/mol.

    • LivThe breakdown of glucose to carbon dioxide and water involves oxidation-reduction or redox reactions.

    • Only A and B are correct.

    • A, B, and C are correct.

    Correct Answer
    A. A, B, and C are correct.

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  • Jan 22, 2024
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    Brownie2007

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