AP Biology Chapter 8 Practice Test

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AP Biology Chapter 8 Practice Test - Quiz

Are you taking AP classes? You will find our ' AP Biology Chapter 8 Practice Test ' super helpful. Ap classes can be challenging; hence, preparing well in advance is necessary. Our quiz is designed to test your knowledge of various course topics. The quiz can be an excellent way to prepare for your AP class examinations. Don't forget to attempt this quiz honestly to get your immediate scores. Study hard, and all the very best!


Questions and Answers
  • 1. 

    Which of the following describes some aspect of metabolism?

    • A.

      Synthesis of macromolecules

    • B.

      Breakdown of macromolecules

    • C.

      Control of enzyme activity

    • D.

      Synthesis of macromolecules and breakdown of macromolecules

    • E.

      Synthesis of macromolecules, breakdown of macromolecules, and control of enzyme activity

    Correct Answer
    E. Synthesis of macromolecules, breakdown of macromolecules, and control of enzyme activity
    Explanation
    The correct answer is synthesis of macromolecules, breakdown of macromolecules, and control of enzyme activity. This answer includes all three aspects of metabolism. Metabolism involves the synthesis of macromolecules, such as proteins, nucleic acids, and carbohydrates, which are essential for cell function and growth. It also involves the breakdown of macromolecules, such as the breakdown of carbohydrates into glucose for energy production. Additionally, metabolism involves the control of enzyme activity, which regulates the speed and efficiency of metabolic reactions.

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  • 2. 

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

    • A.

      Catalysis

    • B.

      Metabolism

    • C.

      Anabolism

    • D.

      Dehydration

    • E.

      Catabolism

    Correct Answer
    E. Catabolism
    Explanation
    Catabolism is the most precise term that describes the cellular process of breaking down large molecules into smaller ones. It involves the breakdown of complex molecules, such as carbohydrates, proteins, and fats, into simpler compounds, releasing energy in the process. This process is essential for providing energy to cells and is a key part of metabolism. Catalysis refers to the acceleration of chemical reactions by a catalyst, while anabolism involves the synthesis of complex molecules from simpler ones. Dehydration is the removal of water molecules.

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  • 3. 

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

    • A.

      They do not depend on enzymes.

    • B.

      They consume energy to build up polymers from monomers.

    • C.

      They release energy as they degrade polymers to monomers.

    • D.

      They lead to the synthesis of catabolic compounds.

    • E.

      They do not depend on enzymes and they consume energy to build up polymers from monomers.

    Correct Answer
    C. They release energy as they degrade polymers to monomers.
    Explanation
    Catabolic pathways are metabolic pathways that involve the breakdown of larger molecules into smaller ones. This process releases energy, which is why the statement "They release energy as they degrade polymers to monomers" is correct. The other statements are incorrect because catabolic pathways do depend on enzymes, they do not consume energy to build up polymers from monomers, and they do not lead to the synthesis of catabolic compounds.

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  • 4. 

    Which of the following is (are) true for anabolic pathways?

    • A.

      They do not depend on enzymes.

    • B.

      They are highly regulated sequences of chemical reactions.

    • C.

      They consume energy to build up polymers from monomers.

    • D.

      They release energy as they degrade polymers to monomers.

    • E.

      They are highly regulated sequences of chemical reactions and they consume energy to build up polymers from monomers.

    Correct Answer
    E. They are highly regulated sequences of chemical reactions and they consume energy to build up polymers from monomers.
    Explanation
    Anabolic pathways are highly regulated sequences of chemical reactions that consume energy to build up polymers from monomers. This means that they require specific enzymes to catalyze the reactions and regulate the flow of molecules, ensuring that the process occurs in a controlled manner. Additionally, anabolic pathways require energy input, usually in the form of ATP, to drive the synthesis of larger molecules from smaller building blocks. Therefore, the correct answer is that anabolic pathways are highly regulated sequences of chemical reactions and they consume energy to build up polymers from monomers.

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  • 5. 

    Which of the following is a statement of the first law of thermodynamics?

    • A.

      Energy cannot be created or destroyed.

    • B.

      The entropy of the universe is decreasing.

    • C.

      The entropy of the universe is constant.

    • D.

      Kinetic energy is stored energy that results from the specific arrangement of matter.

    • E.

      Energy cannot be transferred or transformed.

    Correct Answer
    A. Energy cannot be created or destroyed.
    Explanation
    The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or transformed from one form to another. This principle is a fundamental concept in physics and is applicable to all systems and processes involving energy. It means that the total amount of energy in a closed system remains constant, even though it may change from one form to another. This law is supported by numerous experimental observations and is a cornerstone of the field of thermodynamics.

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  • 6. 

    The first law of thermodynamics states that energy can be neither created nor destroyed.  For living organisms, which of the following is an important consequence of the first law?

    • A.

      The energy content of an organism is constant.

    • B.

      The organism ultimately must obtain all of the necessary energy for life from its environment.

    • C.

      The entropy of an organism decreases with time as the organism grows in complexity.

    • D.

      Organisms are unable to transform energy.

    • E.

      Life does not obey the first law of thermodynamics.

    Correct Answer
    B. The organism ultimately must obtain all of the necessary energy for life from its environment.
    Explanation
    The first law of thermodynamics states that energy can neither be created nor destroyed, only transferred or converted from one form to another. This means that the energy content of an organism remains constant. However, since energy cannot be created within the organism, it must obtain all the necessary energy for life from its environment. This is an important consequence of the first law as it highlights the dependence of organisms on external sources of energy for their survival and functioning.

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  • 7. 

    According to the first law of thermodynamics,

    • A.

      The universe loses energy because of heat production.

    • B.

      Systems rich in energy are intrinsically unstable and will give up energy with time.

    • C.

      Energy can be neither created nor destroyed.

    • D.

      The universe loses energy because of heat production and systems rich in energy are intrinsically unstable and will give up energy with time.

    • E.

      The universe loses energy because of heat production and systems rich in energy are intrinsically unstable, will give up energy with time, and energy can be neither created nor destroyed.

    Correct Answer
    C. Energy can be neither created nor destroyed.
    Explanation
    The first law of thermodynamics states that energy can neither be created nor destroyed, but can only be transferred or transformed from one form to another. This principle is also known as the law of conservation of energy. It implies that the total energy of a closed system remains constant over time. The other statements in the question, such as the universe losing energy due to heat production and systems giving up energy with time, are not necessarily true according to the first law of thermodynamics.

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  • 8. 

    Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism.  How does this relate to the second law of thermodynamics?

    • A.

      Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.

    • B.

      Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is balanced by an increase in the entropy of the universe.

    • C.

      Living organisms do not follow the laws of thermodynamics.

    • D.

      As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.

    • E.

      Living organisms are able to transform energy into entropy.

    Correct Answer
    D. As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.
    Explanation
    The answer explains that as organisms grow, they create more disorder in their environment, which outweighs the decrease in entropy associated with their growth. This is in line with the second law of thermodynamics, which states that entropy must increase with time.

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  • 9. 

    Which of the following statements about metabolism is incorrect?

    • A.

      Metabolism is an emergent property of life at the level of organisms.

    • B.

      Metabolism manages the utilization of materials and energy resources.

    • C.

      The uptake of water associated with the hydrolysis of biological polymers is part of metabolism.

    • D.

      Metabolism depends on a constant supply of energy.

    • E.

      None of these statements about metabolism is incorrect.

    Correct Answer
    A. Metabolism is an emergent property of life at the level of organisms.
    Explanation
    Metabolism is not an emergent property of life at the level of organisms. It is a fundamental property that is present in all living organisms, from the simplest bacteria to complex multicellular organisms. Metabolism refers to the chemical processes that occur within cells to maintain life, including the breakdown of molecules for energy, the synthesis of new molecules, and the elimination of waste products. It is not something that emerges at a certain level of organization, but rather a universal characteristic of life.

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  • 10. 

    Whenever energy is transformed, there is always an increase in the

    • A.

      Free energy of the system.

    • B.

      Free energy of the universe.

    • C.

      Entropy of the system.

    • D.

      Entropy of the universe.

    • E.

      Enthalpy of the universe.

    Correct Answer
    D. Entropy of the universe.
    Explanation
    Whenever energy is transformed, there is always an increase in the entropy of the universe. Entropy is a measure of the disorder or randomness in a system. According to the second law of thermodynamics, the entropy of an isolated system always increases over time. When energy is transformed, it tends to disperse and spread out, leading to an increase in the overall entropy of the universe. This principle applies to all energy transformations, whether it is in a chemical reaction, a physical process, or any other form of energy conversion.

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  • 11. 

    Which of the following statements is a logical consequence of the second law of thermodynamics?

    • A.

      If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe.

    • B.

      If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe.

    • C.

      Every energy transfer requires activation energy from the environment.

    • D.

      Every chemical reaction must increase the total entropy of the universe.

    • E.

      Energy can be transferred or transformed, but it cannot be created or destroyed.

    Correct Answer
    D. Every chemical reaction must increase the total entropy of the universe.
    Explanation
    The second law of thermodynamics states that the entropy of an isolated system will always increase over time. Entropy is a measure of the disorder or randomness in a system. In a chemical reaction, the molecules rearrange themselves, leading to an increase in the overall disorder of the system. This increase in disorder corresponds to an increase in entropy. Since the second law of thermodynamics applies to the universe as a whole, every chemical reaction must increase the total entropy of the universe.

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  • 12. 

    Which of the following statements correctly describe(s) some aspect of energy in living organisms?

    • A.

      Living organisms can convert energy among several different forms.

    • B.

      Living organisms can use energy to do work.

    • C.

      Organisms expend energy in order to decrease their entropy.

    • D.

      Living organisms can convert energy among several different forms and can use energy to do work.

    • E.

      Living organisms can convert energy among several different forms, can use energy to do work and expend energy in order to decrease their entropy.

    Correct Answer
    E. Living organisms can convert energy among several different forms, can use energy to do work and expend energy in order to decrease their entropy.
    Explanation
    Living organisms have the ability to convert energy from one form to another, such as chemical energy to mechanical energy. They also utilize energy to perform various tasks or work, such as movement, growth, and reproduction. Additionally, living organisms expend energy to maintain order and decrease their entropy, which is the measure of disorder in a system. Therefore, the correct answer states that living organisms can convert energy among different forms, use energy to do work, and expend energy to decrease their entropy.

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  • 13. 

    Which of the following statements is not representative of the second law of thermodynamics?

    • A.

      Conversion of energy from one form to another is always accompanied by some loss of free energy.

    • B.

      Heat represents a form of energy that cannot be used by most organisms to do work.

    • C.

      Without an input of energy, organisms would tend towards increasing entropy.

    • D.

      Cells require a constant input of energy to maintain their high level of organization.

    • E.

      Every energy transformation by a cell decreases the entropy of the universe.

    Correct Answer
    E. Every energy transformation by a cell decreases the entropy of the universe.
    Explanation
    The second law of thermodynamics states that in any energy conversion or transfer, there is always some loss of free energy. This loss of free energy is usually in the form of heat, which cannot be used by most organisms to do work. Additionally, without an input of energy, organisms tend towards increasing entropy, which refers to a measure of disorder or randomness in a system. Cells require a constant input of energy to maintain their high level of organization. However, every energy transformation by a cell does not decrease the entropy of the universe. Instead, it contributes to the overall increase in entropy, as energy is constantly being converted and dispersed in various forms.

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  • 14. 

    Which of the following forms of energy is least available to accomplish cellular work?

    • A.

      Light energy

    • B.

      Electrical energy

    • C.

      Thermal energy (heat)

    • D.

      Mechanical energy

    • E.

      Potential energy

    Correct Answer
    C. Thermal energy (heat)
    Explanation
    Thermal energy (heat) is the least available form of energy to accomplish cellular work because it is the most disordered and difficult to convert into usable energy. In cellular processes, energy is typically harnessed and transformed through chemical reactions, and thermal energy is often lost as waste heat during these conversions. In contrast, other forms of energy such as light, electrical, mechanical, and potential energy can be more easily converted and utilized by cells for various metabolic activities.

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  • 15. 

    Which of the following types of reactions would decrease the entropy within a cell?

    • A.

      Dehydration reactions

    • B.

      Hydrolysis

    • C.

      Respiration

    • D.

      Digestion

    • E.

      Catabolism

    Correct Answer
    A. Dehydration reactions
    Explanation
    Dehydration reactions involve the removal of water molecules, resulting in the formation of larger molecules. This process reduces the randomness or disorder within a cell, leading to a decrease in entropy. In contrast, hydrolysis, respiration, digestion, and catabolism involve the breakdown of molecules or the release of energy, which generally increase the disorder and entropy within a cell.

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  • 16. 

    According to the second law of thermodynamics, which of the following statements is incorrect?

    • A.

      The synthesis of large molecules from small molecules is exergonic.

    • B.

      Earth is an open system.

    • C.

      Life exists at the expense of energy derived from its environment.

    • D.

      A living cell can never function as a closed system.

    • E.

      Every chemical reaction in a cell results in a loss of free energy.

    Correct Answer
    A. The synthesis of large molecules from small molecules is exergonic.
    Explanation
    According to the second law of thermodynamics, the synthesis of large molecules from small molecules is endergonic, not exergonic. This is because the process requires an input of energy to overcome the increase in entropy that occurs when smaller molecules combine to form larger ones. Exergonic reactions, on the other hand, release energy.

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  • 17. 

    The organization of organisms has become increasingly complex with time.  This statement

    • A.

      Is consistent with the second law of thermodynamics.

    • B.

      Requires that due to evolution, the entropy of the universe increased.

    • C.

      Is based on the fact that organisms function as closed systems.

    • D.

      Is consistent with the second law of thermodynamics and requires that due to evolution, the entropy of the universe increased.

    • E.

      Is consistent with the second law of thermodynamics, requires that due to evolution, the entropy of the universe increased, and is based on the fact that organisms function as closed systems.

    Correct Answer
    A. Is consistent with the second law of thermodynamics.
    Explanation
    The statement "The organization of organisms has become increasingly complex with time" is consistent with the second law of thermodynamics. According to the second law, in a closed system, entropy (disorder) tends to increase over time. However, living organisms are able to maintain and increase their organization and complexity by taking in energy from their surroundings and using it to perform work. This process is known as entropy reduction or negentropy. Therefore, the increasing complexity of organisms does not violate the second law of thermodynamics, but rather is made possible by the energy flow and work performed within the system.

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  • 18. 

    The mathematical expression for the change in free energy of a system is:  ΔG = ΔH – TΔS.  Which of the following is (are) incorrect?

    • A.

      ΔS is the change in entropy, a measure of randomness.

    • B.

      ΔH is the change in enthalpy, the energy available to do work.

    • C.

      ΔG is the change in free energy.

    • D.

      T is the absolute temperature.

    • E.

      ΔS is the change in entropy, a measure of randomness, and ΔH is the change in enthalpy, the energy available to do work.

    Correct Answer
    B. ΔH is the change in enthalpy, the energy available to do work.
    Explanation
    The given answer is incorrect because ΔH is not the energy available to do work, but rather the change in enthalpy. Enthalpy is a measure of the total heat content of a system. The energy available to do work is represented by ΔG, the change in free energy.

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  • 19. 

    What is the change in free energy of a system at chemical equilibrium?

    • A.

      Slightly increasing

    • B.

      Greatly increasing

    • C.

      Slightly decreasing

    • D.

      Greatly decreasing

    • E.

      No net change

    Correct Answer
    E. No net change
    Explanation
    At chemical equilibrium, the forward and reverse reactions occur at the same rate, resulting in no net change in the concentrations of reactants and products. Since the change in free energy is directly related to the change in concentration, if there is no change in concentration, there will also be no change in free energy. Therefore, the change in free energy of a system at chemical equilibrium is no net change.

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  • 20. 

    Which of the following is true for all exergonic reactions?

    • A.

      The products have more total energy than the reactants.

    • B.

      The reaction proceeds with a net release of free energy.

    • C.

      Some reactants will be converted to products.

    • D.

      A net input of energy from the surroundings is required for the reactions to proceed.

    • E.

      The reactions are nonspontaneous.

    Correct Answer
    B. The reaction proceeds with a net release of free energy.
    Explanation
    Exergonic reactions are characterized by a net release of free energy. This means that the products of the reaction have less energy than the reactants, resulting in a spontaneous reaction that releases energy to the surroundings. Therefore, the statement "The reaction proceeds with a net release of free energy" is true for all exergonic reactions.

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  • 21. 

    Chemical equilibrium is relatively rare in living cells.  Which of the following could be an example of a reaction at chemical equilibrium in a cell?

    • A.

      A reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium

    • B.

      A chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings

    • C.

      An endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment

    • D.

      A chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive

    • E.

      There is no possibility of having chemical equilibrium in any living cell.

    Correct Answer
    D. A chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive
  • 22. 

    Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein?

    • A.

      +ΔH, +ΔS, +ΔG

    • B.

      +ΔH, -ΔS, -ΔG

    • C.

      +ΔH, -ΔS, +ΔG

    • D.

      -ΔH, -ΔS, +ΔG

    • E.

      -ΔH, +ΔS, +ΔG

    Correct Answer
    C. +ΔH, -ΔS, +ΔG
    Explanation
    The formation of a protein from amino acids is an endothermic process (+ΔH) because energy is required to break the bonds between the amino acids and form new bonds in the protein. The process also results in a decrease in entropy (-ΔS) because the amino acids are becoming more ordered and organized in the protein structure. Lastly, the process is not spontaneous and requires energy input, so the change in free energy is positive (+ΔG).

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  • 23. 

    When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows:

    • A.

      +ΔG, +ΔH, +ΔS

    • B.

      +ΔG, +ΔH, -ΔS

    • C.

      +ΔG, -ΔH, -ΔS

    • D.

      -ΔG, +ΔH, +ΔS

    • E.

      -ΔG, -ΔH, -ΔS

    Correct Answer
    B. +ΔG, +ΔH, -ΔS
    Explanation
    When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the process requires energy input (ΔH) and results in an increase in the total energy (ΔG). This is indicated by the "+ΔH" and "+ΔG" options. However, the process also leads to a decrease in entropy (ΔS) as the glucose monomers become more ordered in the polymer structure. This is indicated by the "-ΔS" option. Therefore, the correct answer is "+ΔG, +ΔH, -ΔS" as it accurately represents the changes in free energy, total energy, and entropy during the formation of a cellulose polymer.

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  • 24. 

    A chemical reaction that has a positive ΔG is correctly described as

    • A.

      Endergonic.

    • B.

      Endothermic.

    • C.

      Enthalpic.

    • D.

      Spontaneous.

    • E.

      Exothermic.

    Correct Answer
    A. Endergonic.
    Explanation
    A chemical reaction that has a positive ΔG is correctly described as endergonic. This means that the reaction requires an input of energy in order to proceed. It is the opposite of exergonic reactions, which release energy. Endothermic refers to reactions that absorb heat from their surroundings, while enthalpic refers to changes in the total energy of a system. Spontaneous reactions occur without an input of energy, but since the question states that ΔG is positive, it cannot be spontaneous.

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  • 25. 

    Why is ATP an important molecule in metabolism?

    • A.

      Its hydrolysis provides an input of free energy for exergonic reactions.

    • B.

      It provides energy coupling between exergonic and endergonic reactions.

    • C.

      Its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy.

    • D.

      Its hydrolysis provides an input of free energy for exergonic reactions and it provides energy coupling between exergonic and endergonic reactions.

    • E.

      Its hydrolysis provides an input of free energy for exergonic reactions and it provides energy coupling between exergonic, endergonic reactions, and its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy. .

    Correct Answer
    B. It provides energy coupling between exergonic and endergonic reactions.
    Explanation
    ATP is an important molecule in metabolism because it provides energy coupling between exergonic and endergonic reactions. This means that it can transfer energy from exergonic reactions (reactions that release energy) to endergonic reactions (reactions that require energy). By doing so, ATP helps to drive the energy-requiring processes in the cell, such as active transport, synthesis of macromolecules, and muscle contraction. This energy transfer is made possible by the high-energy phosphate bonds in ATP, which can be broken through hydrolysis to release the stored energy.

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  • 26. 

    The hydrolysis of ATP to ADP and inorganic phosphate (ATP + H2O → ADP + Pi )

    • A.

      Has a ΔG of about -7 kcal/mol under standard conditions.

    • B.

      Involves hydrolysis of a terminal phosphate bond of ATP.

    • C.

      Can occur spontaneously under appropriate conditions.

    • D.

      Has a ΔG of about -7 kcal/mol under standard conditions and involves hydrolysis of a terminal phosphate bond of ATP.

    • E.

      Has a ΔG of about -7 kcal/mol under standard conditions, involves hydrolysis of a terminal phosphate bond of ATP, and can occur spontaneously under appropriate conditions.

    Correct Answer
    E. Has a ΔG of about -7 kcal/mol under standard conditions, involves hydrolysis of a terminal phosphate bond of ATP, and can occur spontaneously under appropriate conditions.
    Explanation
    The correct answer is that the hydrolysis of ATP to ADP and inorganic phosphate has a ΔG of about -7 kcal/mol under standard conditions, involves hydrolysis of a terminal phosphate bond of ATP, and can occur spontaneously under appropriate conditions. This means that the reaction releases energy and is favorable under normal physiological conditions. The hydrolysis of the terminal phosphate bond is the specific reaction that occurs, breaking the bond between the last phosphate group and the rest of the ATP molecule. This reaction can occur spontaneously without the need for additional energy input.

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  • 27. 

    When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP.  Which of the following is the best explanation for this observation?

    • A.

      Cells are open systems, but a test tube is a closed system.

    • B.

      Cells are less efficient at heat production than nonliving systems.

    • C.

      The hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube.

    • D.

      The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes.

    • E.

      Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat.

    Correct Answer
    E. Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat.
    Explanation
    Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat. This is the best explanation because cells have various metabolic processes that utilize the energy released from ATP hydrolysis for other functions, such as muscle contraction, active transport, and synthesis of macromolecules. In contrast, a test tube is a closed system where the energy released from ATP hydrolysis is mainly dissipated as heat, resulting in a higher heat liberation compared to cells.

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  • 28. 

    ATP generally energizes a cellular process by

    • A.

      Releasing heat upon hydrolysis.

    • B.

      Acting as a catalyst.

    • C.

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

    • D.

      Breaking a high-energy bond.

    • E.

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

    Correct Answer
    C. Coupling free energy released by ATP hydrolysis to free energy needed by other reactions.
    Explanation
    ATP is a molecule that stores and releases energy in cells. When ATP is hydrolyzed, it breaks down into ADP and inorganic phosphate, releasing energy in the process. This energy is then used to drive other cellular reactions that require energy. Therefore, ATP couples the free energy released during its hydrolysis to provide the energy needed by other reactions in the cell.

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  • 29. 

    Which of the following reactions is most likely to be coupled to the reaction ATP + H2O →ADP + Pi (ΔG = -7.3 kcal/mol)?

    • A.

      A + Pi → AP (ΔG = +10 kcal/mol)

    • B.

      B + Pi → BP (ΔG = +8 kcal/mol)

    • C.

      CP → C + Pi (ΔG = -4 kcal/mol)

    • D.

      DP → D + Pi (ΔG = -10 kcal/mol)

    • E.

      E + Pi → EP (ΔG = +5 kcal/mol)

    Correct Answer
    E. E + Pi → EP (ΔG = +5 kcal/mol)
    Explanation
    The reaction E + Pi → EP with a ΔG of +5 kcal/mol is the most likely to be coupled to the reaction ATP + H2O → ADP + Pi with a ΔG of -7.3 kcal/mol. Coupling reactions involve combining an energetically unfavorable reaction (ΔG > 0) with an energetically favorable reaction (ΔG < 0) to drive the overall process. In this case, the ΔG of the coupled reaction (ΔG = -7.3 + 5 = -2.3 kcal/mol) is still negative, indicating that the overall reaction is energetically favorable.

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  • 30. 

    Which of the following is most similar in structure to ATP?

    • A.

      An anabolic steroid

    • B.

      A DNA helix

    • C.

      RNA nucleotides

    • D.

      An amino acid with three phosphate groups attached

    • E.

      A phospholipid

    Correct Answer
    C. RNA nucleotides
    Explanation
    ATP (adenosine triphosphate) is a nucleotide that consists of a nitrogenous base (adenine), a sugar (ribose), and three phosphate groups. Similarly, RNA nucleotides also consist of a nitrogenous base (adenine, guanine, cytosine, or uracil), a sugar (ribose), and a phosphate group. Therefore, RNA nucleotides are most similar in structure to ATP.

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  • 31. 

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

    • A.

      Feedback regulation

    • B.

      Bioenergetics

    • C.

      Energy coupling

    • D.

      Entropy

    • E.

      Cooperativity

    Correct Answer
    C. Energy coupling
    Explanation
    Energy coupling is the term used to describe the transfer of free energy from catabolic pathways (which break down molecules and release energy) to anabolic pathways (which build up molecules and require 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 and metabolic processes in living organisms.

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  • 32. 

    Which of the following statements is true concerning catabolic pathways?

    • A.

      They combine molecules into more energy-rich molecules.

    • B.

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

    • C.

      They are endergonic.

    • D.

      They are spontaneous and do not need enzyme catalysis.

    • E.

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

    Correct Answer
    B. 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 drive anabolic pathways, which build complex molecules from simpler ones. The statement that catabolic pathways are usually coupled with anabolic pathways and supply energy in the form of ATP is true because ATP is the primary energy currency in cells and is often generated during catabolism to be used in anabolism.

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  • 33. 

    Which of the following statements regarding ATP is (are) correct?

    • A.

      ATP serves as a main energy shuttle inside cells.

    • B.

      ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants.

    • C.

      The regeneration of ATP from ADP and phosphate is an endergonic reaction.

    • D.

      ATP serves as a main energy shuttle inside cells and ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants.

    • E.

      ATP serves as a main energy shuttle inside cells, ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants, and regeneration of ATP from ADP and phosphate is an endergonic reaction.

    Correct Answer
    E. ATP serves as a main energy shuttle inside cells, ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants, and regeneration of ATP from ADP and phosphate is an endergonic reaction.
    Explanation
    The correct answer is that ATP serves as a main energy shuttle inside cells, ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants, and regeneration of ATP from ADP and phosphate is an endergonic reaction. This answer encompasses all the correct statements mentioned in the question. ATP is indeed a crucial energy carrier in cells, transferring energy to various cellular processes through the transfer of phosphate groups. The regeneration of ATP from ADP and phosphate requires energy input, making it an endergonic reaction.

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  • 34. 

    Which of the following statements is (are) true about enzyme-catalyzed reactions?

    • A.

      The reaction is faster than the same reaction in the absence of the enzyme.

    • B.

      The free energy change of the reaction is the same as the reaction in the absence of the enzyme.

    • C.

      The reaction always goes in the direction toward chemical equilibrium.

    • D.

      The reaction is faster than the same reaction in the absence of the enzyme and the free energy change of the reaction is the same as the reaction in the absence of the enzyme.

    • E.

      The reaction always goes in the direction toward chemical equilibrium, the free energy change of the reaction is the same as the reaction in the absence of the enzyme, and the reaction always goes in the direction toward chemical equilibrium.

    Correct Answer
    A. The reaction is faster than the same reaction in the absence of the enzyme.
    Explanation
    Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction to occur. This means that the reaction can proceed at a faster rate in the presence of an enzyme compared to the same reaction in the absence of the enzyme. Therefore, the statement "The reaction is faster than the same reaction in the absence of the enzyme" is true.

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  • 35. 

    How can one increase the rate of a chemical reaction?

    • A.

      Increase the activation energy needed.

    • B.

      Cool the reactants.

    • C.

      Decrease the concentration of the reactants.

    • D.

      Add a catalyst.

    • E.

      Increase the entropy of the reactants.

    Correct Answer
    D. Add a catalyst.
    Explanation
    Adding a catalyst can increase the rate of a chemical reaction by providing an alternative pathway with lower activation energy. A catalyst does not get consumed in the reaction and can be used repeatedly, making it an effective way to speed up reactions without being used up itself.

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  • 36. 

    Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose.  The hydrolysis of sucrose by the enzyme sucrase results in

    • A.

      Bringing glucose and fructose together to form sucrose.

    • B.

      The release of water from sucrose as the bond between glucose and fructose is broken.

    • C.

      Breaking the bond between glucose and fructose and forming new bonds from the atoms of water.

    • D.

      Production of water from the sugar as bonds are broken between the glucose monomers.

    • E.

      Utilization of water as a covalent bond is formed between glucose and fructose to form sucrase.

    Correct Answer
    C. Breaking the bond between glucose and fructose and forming new bonds from the atoms of water.
    Explanation
    Sucrose is a disaccharide made up of glucose and fructose. When sucrase enzyme acts on sucrose, it breaks the bond between glucose and fructose. In this process, water molecules are used to break the bond and new bonds are formed between the atoms of water. Therefore, the correct answer is "breaking the bond between glucose and fructose and forming new bonds from the atoms of water."

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  • 37. 

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

    • A.

      Entropy.

    • B.

      Activation energy.

    • C.

      Endothermic level.

    • D.

      Heat content.

    • E.

      Free-energy content.

    Correct Answer
    B. Activation energy.
    Explanation
    In order for reactants to form products in a chemical reaction, they must first overcome a thermodynamic barrier known as the reaction's activation energy. This energy barrier represents the minimum amount of energy required for the reactants to reach a transition state and initiate the formation of products. By surpassing this activation energy, the reactants can proceed towards a lower energy state and form the desired products. The other options, such as entropy, endothermic level, heat content, and free-energy content, are not directly related to the initial energy barrier that needs to be overcome for the reaction to occur.

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  • 38. 

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

    • A.

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

    • B.

      The hydrolysis of starch to sugar is endergonic.

    • C.

      The activation energy barrier for this reaction cannot be surmounted.

    • D.

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

    • E.

      Starch hydrolysis is nonspontaneous.

    Correct Answer
    C. The activation energy barrier for this reaction cannot be surmounted.
    Explanation
    The activation energy barrier refers to the minimum amount of energy required for a chemical reaction to occur. In this case, the hydrolysis of starch to form simple sugars requires breaking the bonds between the glucose molecules in starch. This breaking of bonds requires a certain amount of energy to overcome the activation energy barrier. At room temperature, the starch solution does not have enough energy to overcome this barrier, which is why it does not readily decompose into a solution of simple sugars.

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  • 39. 

    Which of the following statements regarding enzymes is true?

    • A.

      Enzymes decrease the free energy change of a reaction.

    • B.

      Enzymes increase the rate of a reaction.

    • C.

      Enzymes change the direction of chemical reactions.

    • D.

      Enzymes are permanently altered by the reactions they catalyze.

    • E.

      Enzymes prevent changes in substrate concentrations.

    Correct Answer
    B. Enzymes increase the rate of a reaction.
    Explanation
    Enzymes are biological catalysts that increase the rate of a reaction by lowering the activation energy required for the reaction to occur. They do this by binding to the substrate and facilitating the formation of the transition state, which allows the reaction to proceed more quickly. Enzymes do not alter the free energy change of a reaction, change the direction of chemical reactions, or prevent changes in substrate concentrations. Additionally, enzymes are not permanently altered by the reactions they catalyze and can be reused multiple times.

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  • 40. 

    Which of the following is not true of enzymes?

    • A.

      Enzyme catalysis is dependent on the pH and temperature of the reaction environment.

    • B.

      Enzyme catalysis is dependent on the three-dimensional structure or conformation of the enzyme.

    • C.

      Enzymes provide activation energy for the reaction they catalyze.

    • D.

      Enzymes are composed primarily of protein, but they may bind nonprotein cofactors.

    • E.

      Enzyme activity can be inhibited if the enzyme's allosteric site is bound with a noncompetitive inhibitor.

    Correct Answer
    C. Enzymes provide activation energy for the reaction they catalyze.
    Explanation
    Enzymes do not provide activation energy for the reaction they catalyze. Instead, enzymes lower the activation energy required for a reaction to occur, which increases the rate of the reaction. This is achieved by binding to the reactants and bringing them into close proximity, allowing them to interact more easily and form the products. The activation energy is the energy barrier that needs to be overcome for a reaction to proceed, and enzymes help to overcome this barrier by stabilizing the transition state of the reaction.

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  • 41. 

    An enzyme catalyzes a reaction by

    • A.

      Supplying the energy to speed up a reaction.

    • B.

      Lowering the energy of activation of a reaction.

    • C.

      Lowering the ΔG of a reaction.

    • D.

      Changing the equilibrium of a spontaneous reaction.

    • E.

      Increasing the amount of free energy of a reaction.

    Correct Answer
    B. Lowering the energy of activation of a reaction.
    Explanation
    Enzymes lower the energy of activation of a reaction, which is the energy required to initiate a chemical reaction. By lowering this energy barrier, enzymes enable the reaction to occur more easily and at a faster rate. This is achieved by stabilizing the transition state of the reaction, making it easier for the reactant molecules to reach this state and proceed to form the products. Therefore, the correct answer is "lowering the energy of activation of a reaction."

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  • 42. 

    Which of these statements regarding enzymes is false?

    • A.

      Enzymes are proteins that function as catalysts.

    • B.

      Enzymes display specificity for certain molecules with which they interact.

    • C.

      Enzymes provide activation energy for the reactions they catalyze.

    • D.

      The activity of enzymes can be regulated by other molecules.

    • E.

      An enzyme may be used many times over for a specific reaction.

    Correct Answer
    C. Enzymes provide activation energy for the reactions they catalyze.
    Explanation
    Enzymes do not provide activation energy for the reactions they catalyze. Instead, they lower the activation energy required for the reaction to occur, making it easier for the reaction to proceed. This allows the reaction to happen more quickly and efficiently.

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  • 43. 

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

    • A.

      -40 kcal/mol

    • B.

      -20 kcal/mol

    • C.

      0 kcal/mol

    • D.

      +20 kcal/mol

    • E.

      +40 kcal/mol

    Correct Answer
    B. -20 kcal/mol
    Explanation
    When the amount of enzyme in a reaction is doubled, it does not affect the value of ΔG. ΔG represents the change in free energy during a reaction and is independent of the amount of enzyme present. Therefore, the ΔG for the new reaction will still be -20 kcal/mol.

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  • 44. 

    The active site of an enzyme is the region that

    • A.

      Binds allosteric regulators of the enzyme.

    • B.

      Is involved in the catalytic reaction of the enzyme.

    • C.

      Binds the products of the catalytic reaction.

    • D.

      Is inhibited by the presence of a coenzyme or a cofactor.

    • E.

      Binds allosteric regulators of the enzyme and is involved in the catalytic reaction of the enzyme.

    Correct Answer
    B. Is involved in the catalytic reaction of the enzyme.
    Explanation
    The active site of an enzyme is the region that is involved in the catalytic reaction of the enzyme. This means that the active site is where the enzyme binds to its substrate and facilitates the chemical reaction to occur. It is at the active site that the enzyme's specific shape and chemical properties allow it to interact with the substrate and convert it into a product. Therefore, the active site is crucial for the enzyme's catalytic function.

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  • 45. 

    According to the induced fit hypothesis of enzyme catalysis, which of the following is CORRECT?

    • A.

      The binding of the substrate depends on the shape of the active site.

    • B.

      Some enzymes change their structure when activators bind to the enzyme.

    • C.

      A competitive inhibitor can outcompete the substrate for the active site.

    • D.

      The binding of the substrate changes the shape of the enzyme's active site.

    • E.

      The active site creates a microenvironment ideal for the reaction.

    Correct Answer
    D. The binding of the substrate changes the shape of the enzyme's active site.
    Explanation
    According to the induced fit hypothesis of enzyme catalysis, the binding of the substrate changes the shape of the enzyme's active site. This means that the active site is not a rigid structure, but rather it can undergo conformational changes upon substrate binding. These changes in the active site allow for a more precise and complementary fit between the enzyme and the substrate, enhancing the catalytic efficiency of the enzyme.

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  • 46. 

    Many different things can alter enzyme activity.  Which of the following underlie all types of enzyme regulation?

    • A.

      Changes in the activation energy of the reaction

    • B.

      Changes in the active site of the enzyme

    • C.

      Changes in the free energy of the reaction

    • D.

      Changes in the activation energy of the reaction and in the active site of the enzyme

    • E.

      Changes in the activation energy of the reaction, in the active site of the enzyme, and in the free energy of the reaction

    Correct Answer
    D. Changes in the activation energy of the reaction and in the active site of the enzyme
    Explanation
    Enzyme activity can be regulated by changes in the activation energy of the reaction and in the active site of the enzyme. Activation energy refers to the energy required to initiate a chemical reaction, and altering this energy can affect the rate at which the reaction occurs. Changes in the active site of the enzyme can also impact enzyme activity, as the active site is the region where the enzyme binds to its substrate and catalyzes the reaction. Therefore, both changes in activation energy and active site can influence enzyme regulation.

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  • 47. 

    Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    • E.

      5

    Correct Answer
    C. 3
  • 48. 

    Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    • E.

      5

    Correct Answer
    D. 4
    Explanation
    Curve 4 is most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid. This is because curve 4 shows a higher activity level at a low pH, which is characteristic of enzymes that function in acidic environments. The other curves show either no activity or lower activity at low pH, indicating that they are not likely to be enzymes from a human stomach under strongly acid conditions.

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  • 49. 

    Which curve was most likely generated from an enzyme that requires a cofactor?

    • A.

      1

    • B.

      2

    • C.

      4

    • D.

      5

    • E.

      It is not possible to determine whether an enzyme requires a cofactor from these data.

    Correct Answer
    E. It is not possible to determine whether an enzyme requires a cofactor from these data.
    Explanation
    The given question asks which curve is most likely generated from an enzyme that requires a cofactor. However, the answer states that it is not possible to determine whether an enzyme requires a cofactor from the given data. This suggests that the information provided is not sufficient to make a conclusion about the enzyme's requirement for a cofactor. Therefore, the correct answer is that it is not possible to determine whether an enzyme requires a cofactor from these data.

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  • 50. 

    As temperature decreases, the rate of an enzyme-catalyzed reaction also decreases. Which of the following explain(s) why this occurs? 

    • A.

      Fewer substrates have sufficient energy to get over the activation energy barrier.

    • B.

      Motion in the active site of the enzyme is slowed, thus slowing the catalysis of the enzyme.

    • C.

      The motion of the substrate molecules decreases, allowing them to bind more easily to the active site.

    • D.

      Fewer substrates have sufficient energy to get over the activation energy barrier and motion in the active site of the enzyme is slowed, thus slowing the catalysis of the enzyme.

    • E.

      Fewer substrates have sufficient energy to get over the activation energy barrier, motion in the active site of the enzyme is slowed, thus slowing the catalysis of the enzyme, and the motion of the substrate molecules decreases, allowing them to bind more easily to the active site.

    Correct Answer
    D. Fewer substrates have sufficient energy to get over the activation energy barrier and motion in the active site of the enzyme is slowed, thus slowing the catalysis of the enzyme.
    Explanation
    As temperature decreases, the kinetic energy of molecules decreases, resulting in fewer substrates having sufficient energy to overcome the activation energy barrier. This leads to a decrease in the rate of the enzyme-catalyzed reaction. Additionally, lower temperature slows down the motion in the active site of the enzyme, which further contributes to the decrease in catalysis. Therefore, both the decrease in substrate energy and the slowed motion in the active site explain why the rate of the reaction decreases with decreasing temperature.

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Stephen Reinbold |PhD, Biological Sciences |
Biology Expert
Stephen Reinbold has a Ph.D. in Biological Sciences with a particular interest in teaching. He taught General Biology, Environmental Science, Zoology, Genetics, and Anatomy & Physiology for almost thirty years at Metropolitan Community College in Kansas City, Missouri. He particularly enjoyed emphasizing scientific methodology and student research projects. Now, enjoying retirement, he works part-time as an editor while also engaging in online activities.

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