Cellular Energetics Practice Quiz 1

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  • 1/90 Questions

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

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  • 2. 

    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
    Organisms that can exist with light as an energy source and an inorganic form of carbon and other raw materials are called photoautotrophs. This means that these organisms are capable of using sunlight to produce their own food through photosynthesis, using inorganic sources of carbon such as carbon dioxide. They do not rely on consuming other organisms for energy, distinguishing them from heterotrophs. Additionally, they are not classified as decomposers, as decomposers break down organic matter. Therefore, the correct answer is that they are called photoautotrophs.

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  • 3. 

    When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

    • Formation of ATP.

    • Reduction of NAD+.

    • Restoration of the Na+/K+ balance across the membrane.

    • Creation of a proton gradient.

    • Lowering of pH in the mitochondrial matrix.

    Correct Answer
    A. Creation of a proton gradient.
    Explanation
    When hydrogen ions (protons) are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, it creates a concentration gradient or a proton gradient. This gradient represents a difference in the concentration of protons on either side of the membrane. This proton gradient is a form of potential energy that can be used by the ATP synthase enzyme to produce ATP through a process called oxidative phosphorylation. Therefore, the correct answer is the creation of a proton gradient.

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  • 4. 

    Which of the following is true of enzymes?

    • Enzymes may require a nonprotein cofactor or ion for catalysis to take place.

    • Enzyme function is reduced if the three-dimensional structure or conformation of an enzyme is altered.

    • Enzyme function is influenced by physical and chemical environmental factors such as pH and temperature.

    • Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

    • All of the above are true of enzymes.

    Correct Answer
    A. All of the above are true of enzymes.
    Explanation
    Enzymes may require a nonprotein cofactor or ion for catalysis to take place. Enzyme function is reduced if the three-dimensional structure or conformation of an enzyme is altered. Enzyme function is influenced by physical and chemical environmental factors such as pH and temperature. Enzymes increase the rate of chemical reaction by lowering activation energy barriers. Therefore, all of the above statements are true of enzymes.

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  • 5. 

    You have a friend who lost 7 kg (about 15 pounds) of fat on a "low carb" diet. How did the fat leave her body?

    • It was released as CO2 and H2O.

    • Chemical energy was converted to heat and then released.

    • It was converted to ATP, which weighs much less than fat.

    • It was broken down to amino acids and eliminated from the body.

    • It was converted to urine and eliminated from the body.

    Correct Answer
    A. It was released as CO2 and H2O.
    Explanation
    When the body breaks down fat molecules for energy, the carbon atoms in the fat combine with oxygen to form carbon dioxide (CO2) and the hydrogen atoms combine with oxygen to form water (H2O). These waste products are then eliminated from the body through exhalation (CO2) and urine (H2O). Therefore, the fat leaves the body as CO2 and H2O.

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  • 6. 

    A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are not being absorbed by this pigment?

    • Red and yellow

    • Blue and violet

    • Green and yellow

    • Blue, green, and red

    • Green, blue, and violet

    Correct Answer
    A. Red and yellow
    Explanation
    The plant's unique photosynthetic pigment appears reddish yellow, indicating that it absorbs blue and green wavelengths of visible light. Since the pigment is not absorbing red and yellow wavelengths, these colors are reflected or transmitted, making the leaves appear reddish yellow.

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  • 7. 

    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 are metabolic processes that involve the breakdown of complex molecules into simpler ones. These pathways rely on enzymes to catalyze the chemical reactions involved in the breakdown process. They release energy as they degrade polymers to monomers, which can be used by the cell for various purposes. Therefore, the correct answer is "They release energy as they degrade polymers to monomers."

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  • 8. 

    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

    Correct Answer
    A. Catabolic pathways
    Explanation
    Catabolic pathways are the correct answer because they refer to metabolic processes that break down complex molecules to release stored energy. These pathways involve the breakdown of larger molecules into smaller ones, such as the breakdown of carbohydrates, lipids, and proteins through processes like glycolysis, beta oxidation, and protein degradation. This release of energy is essential for various cellular activities and is a fundamental aspect of metabolism. Anabolic pathways, on the other hand, are metabolic processes that build complex molecules from simpler ones, requiring energy input.

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  • 9. 

    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 acts as an electron carrier. ADP is phosphorylated to yield ATP, which is the energy currency of the cell. Light is absorbed and funneled to reaction-center chlorophyll a, which is essential for the initiation of photosynthesis. However, carbon dioxide is not incorporated into PGA (phosphoglycerate), a molecule formed during the Calvin cycle, which is a part of the dark reactions of photosynthesis. Therefore, the correct answer is "carbon dioxide is incorporated into PGA."

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  • 10. 

    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 catabolized to pyruvate. The process involves the breakdown of glucose molecules into two molecules of pyruvate. Most of the energy from glucose is captured and retained in the pyruvate molecules. This energy is stored in the form of high-energy electrons and hydrogen atoms, which are transferred to NAD+ to produce NADH. The NADH molecules carry this energy to the electron transport chain, where it is ultimately used to generate ATP through oxidative phosphorylation. Therefore, the correct answer is retained in the pyruvate.

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  • 11. 

    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 known as the energy currency of the cell because it provides the necessary energy for cellular processes. It achieves this by coupling the free energy released during its hydrolysis (breakdown) to other reactions that require energy. This means that when ATP is hydrolyzed, it releases energy that can be used to drive other reactions in the cell. Therefore, the correct answer is that ATP couples the free energy released by its hydrolysis to the free energy needed by other reactions.

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  • 12. 

    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 to a chemical reaction can increase the rate of the reaction. A catalyst is a substance that speeds up the reaction by providing an alternative pathway with lower activation energy. It does not get consumed in the reaction and can be used repeatedly. By lowering the activation energy, a catalyst allows more reactant molecules to have sufficient energy to overcome the energy barrier and react. This results in an increased rate of reaction without being consumed in the process.

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  • 13. 

    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
    In the citric acid cycle, one molecule of pyruvate is oxidized to produce one molecule of acetyl-CoA. Acetyl-CoA has two carbon atoms. Therefore, as a result of the oxidation of one molecule of pyruvate, two carbon atoms are fed into the citric acid cycle.

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  • 14. 

    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 being oxidized, meaning it is losing electrons and becoming more positively charged. Oxygen (O2) is being reduced, meaning it is gaining electrons and becoming more negatively charged. Therefore, the correct answer is that C6H12O6 is oxidized and O2 is reduced.

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  • 15. 

      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 oxidized to pyruvate. However, only a small amount of the free energy available from the oxidation of glucose is captured in the form of ATP and NADH. Most of the free energy is actually stored in the pyruvate molecules that are produced. This is why only two molecules of NADH are formed during glycolysis, despite the potential for more. The majority of the free energy is still present in the pyruvate, which can then be further metabolized in other pathways to extract more energy.

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  • 16. 

    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 the mitochondria. This occurs as electrons are transferred through a series of protein complexes in the inner mitochondrial membrane, pumping protons from the matrix into the intermembrane space. This creates a concentration gradient of protons, with a higher concentration in the intermembrane space. The protons then flow back into the matrix through ATP synthase, an enzyme that utilizes the energy from this proton gradient to produce ATP through a process called chemiosmosis. Therefore, the correct answer is "the electron transport chain; ATP synthesis."

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  • 17. 

    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
    During aerobic respiration, glucose is completely oxidized to produce carbon dioxide and water. The balanced equation for this process is C6H12O6 + 6O2 → 6CO2 + 6H2O. From the equation, we can see that for each molecule of glucose, 6 molecules of oxygen are required. Therefore, the correct answer is 6.

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  • 18. 

    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 needed to transfer the electrons to NAD+. This is because the transfer of electrons requires energy input, and if the energy released is not greater than the energy required, the reaction will not proceed. Therefore, option C is correct. The other options are incorrect because they do not address the energy requirement for electron transfer.

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  • 19. 

    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 process of breaking down glucose into pyruvate, which occurs in the cytoplasm of cells. It is an anaerobic process, meaning it does not require oxygen, and is the first step in both aerobic and anaerobic respiration. Therefore, glycolysis normally occurs whether or not oxygen is present.

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  • 20. 

    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 inside the chloroplast where various metabolic reactions occur. The Calvin cycle is a series of biochemical reactions that take place in the stroma and are responsible for converting carbon dioxide into glucose during photosynthesis. The thylakoid membrane is where the light-dependent reactions occur, while the cytoplasm surrounding the chloroplast and the outer membrane of the chloroplast are not directly involved in the Calvin cycle. The chlorophyll molecule is responsible for capturing light energy, but it is not the site of the Calvin cycle.

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  • 21. 

    Why is ATP an important molecule in metabolism?

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

    • It provides energy coupling between exergonic and endergonic reactions.

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

    • . A and B only

    • A, B and C

    Correct Answer
    A. 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 ATP can transfer energy from exergonic reactions (reactions that release energy) to endergonic reactions (reactions that require energy). By transferring a phosphate group to another molecule, ATP can provide the necessary energy for the endergonic reaction to occur. This energy transfer allows cells to efficiently use and transfer energy, making ATP crucial for various metabolic processes.

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  • 22. 

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

    • 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.

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

    • A and B only

    • A, B, and C

    Correct Answer
    A. A, B, and C
    Explanation
    ATP serves as a main energy shuttle inside cells, as it carries energy between different cellular processes. ATP drives endergonic reactions in the cell by transferring its phosphate group to specific reactants through enzymatic reactions. Additionally, the regeneration of ATP from ADP and phosphate is an endergonic reaction, meaning it requires energy input. Therefore, statements A, B, and C are all correct.

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  • 23. 

    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 is the minimum amount of energy required for a reaction to occur, and it determines the rate at which the reaction proceeds. It is necessary to provide enough energy to break the existing bonds in the reactants and initiate the formation of new bonds in the products. Once the activation energy is surpassed, the reaction can proceed spontaneously. Therefore, activation energy is the correct answer in this case.

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  • 24. 

    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 by lowering the energy of activation, which is the energy required to start a reaction. By lowering this energy barrier, enzymes allow reactions to occur more easily and at a faster rate. This is achieved by providing an alternative reaction pathway with a lower activation energy, making it easier for reactant molecules to reach the necessary energy threshold for the reaction to proceed. Therefore, the correct answer is "lowering the energy of activation of a reaction."

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  • 25. 
    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 Gibbs free energy. The value of G remains the same at -20 kcal/mol.

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  • 26. 

    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 allows the cell to regulate the production of certain molecules by slowing down or stopping the pathway when enough of the end product has been produced. This helps maintain homeostasis and prevent the accumulation of excess molecules. Feedback inhibition is a common regulatory mechanism in many metabolic pathways and is essential for proper cellular function.

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  • 27. 

    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 mitochondrion is responsible for producing ATP through a process called cellular respiration. This process involves multiple steps, including the electron transport chain and ATP synthase, which are mentioned as necessary components in the answer choices. Glycolysis, on the other hand, occurs in the cytoplasm of the cell and does not require the presence of mitochondria. Therefore, enzymes for glycolysis are not necessary for the primary function of the mitochondrion, which is the production of ATP.

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  • 28. 

    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 first step in cellular respiration, where glucose is converted into pyruvate. This process takes place in the cytosol. Fermentation, on the other hand, occurs when there is no oxygen present and pyruvate is converted into either lactate or ethanol, also happening in the cytosol. The other options listed, such as chemiosmosis, oxidation of pyruvate to acetyl CoA, citric acid cycle, and oxidative phosphorylation, all occur in different parts of the cell, such as the mitochondria.

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  • 29. 

    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 (or redox) reaction, the molecule that is reduced gains electrons, which means it is being reduced. On the other hand, the molecule that is oxidized loses electrons, which means it is being oxidized. Therefore, both statements A and B are correct.

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  • 30. 

    A molecule that is phosphorylated

    • Has an increased chemical reactivity; it is primed to do cellular work.

    • Has a decreased chemical reactivity; it is less likely to provide energy for cellular work.

    • Has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.

    • Has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.

    • Has less energy than before its phosphorylation and therefore less energy for cellular work.

    Correct Answer
    A. Has an increased chemical reactivity; it is primed to do cellular work.
    Explanation
    When a molecule is phosphorylated, it means that a phosphate group has been added to it. This addition of a phosphate group increases the chemical reactivity of the molecule. The phosphate group contains high-energy bonds that can be easily broken, releasing energy that can be used for cellular work. Therefore, a phosphorylated molecule is primed and ready to participate in various cellular processes and provide energy for cellular work.

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  • 31. 

    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 second stage of photosynthesis, known as the Calvin cycle, where they provide the energy and reducing power needed to convert carbon dioxide into glucose. ATP is the main energy currency of cells, while NADPH is a coenzyme that carries high-energy electrons used in the synthesis of glucose. Therefore, the production of ATP and NADPH through the light reactions is crucial for the overall process of photosynthesis.

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  • 32. 

    Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be

    • To determine if they have thylakoids in the chloroplasts.

    • To test for liberation of O2 in the light.

    • To test for CO2 fixation in the dark.

    • To do experiments to generate an action spectrum.

    • To test for production of either sucrose or starch.

    Correct Answer
    A. To test for liberation of O2 in the light.
    Explanation
    The best way to detect the lack of photosystem II in these organisms would be to test for liberation of O2 in the light. Photosystem II is responsible for the initial step of photosynthesis, which is the splitting of water molecules and release of oxygen. If an organism lacks photosystem II, it would not be able to produce oxygen during photosynthesis. Therefore, testing for liberation of O2 in the light would indicate whether photosystem II is present or not.

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  • 33. 

    Which metabolic pathway is common to both cellular respiration and fermentation?

    • The oxidation of pyruvate to acetyl CoA

    • The citric acid cycle

    • Oxidative phosphorylation

    • Glycolysis

    • Chemiosmosis

    Correct Answer
    A. Glycolysis
    Explanation
    Glycolysis is the correct answer because it is a metabolic pathway that occurs in both cellular respiration and fermentation. It is the initial step in both processes, where glucose is broken down into pyruvate. In cellular respiration, pyruvate is further oxidized to produce energy through the citric acid cycle and oxidative phosphorylation. In fermentation, pyruvate is converted into other compounds like lactic acid or ethanol, without the involvement of oxygen. Therefore, glycolysis is the common pathway that occurs in both cellular respiration and fermentation.

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  • 34. 

    Where is the electron transport chain found in plant cells?

    • Thylakoid membranes of chloroplasts

    • Stroma of chloroplasts

    • Inner membrane of mitochondria

    • Matrix of mitochondria

    • Cytoplasm

    Correct Answer
    A. Thylakoid membranes of chloroplasts
    Explanation
    The electron transport chain is found in the thylakoid membranes of chloroplasts. This is where the process of photosynthesis takes place in plant cells. The thylakoid membranes contain the pigments and protein complexes necessary for capturing light energy and converting it into chemical energy in the form of ATP and NADPH. The electron transport chain is a series of protein complexes embedded in the thylakoid membranes that transfer electrons and generate a proton gradient, which is used to produce ATP through chemiosmosis.

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  • 35. 

    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 process of losing electrons or gaining oxygen atoms, and in this case, the glucose molecule has lost a hydrogen atom, which is equivalent to losing an electron. Therefore, the correct answer is oxidized.

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  • 36. 

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

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

    • Involves hydrolysis of a terminal phosphate bond of ATP.

    • Can occur spontaneously under appropriate conditions.

    • Only A and B are correct.

    • A, B, and C are correct.

    Correct Answer
    A. A, B, and C are correct.
    Explanation
    The hydrolysis of ATP to ADP and inorganic phosphate has a negative Gibbs free energy (G) value of about -7 kcal/mol under standard conditions, indicating that it is an energetically favorable reaction. This reaction involves the hydrolysis of a terminal phosphate bond of ATP, which releases energy. Additionally, the hydrolysis of ATP can occur spontaneously under appropriate conditions, further supporting the statement that A, B, and C are all correct.

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  • 37. 

    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 larger molecules into smaller ones, releasing energy in the process. This energy is then used to power anabolic pathways, which build up complex molecules from simpler compounds. Therefore, catabolic pathways are usually coupled with anabolic pathways to supply them with energy in the form of ATP.

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  • 38. 

    How many reduced dinucleotides would be produced with four turns of the citric acid cycle?

    • 1 FADH2 and 4 NADH

    • 2 FADH2 and 8 NADH

    • 4 FADH2 and 12 NADH

    • 1 FAD and 4 NAD+

    • 4 FAD+ and 12 NAD+

    Correct Answer
    A. 4 FADH2 and 12 NADH
    Explanation
    In the citric acid cycle, each turn produces 1 FADH2 and 3 NADH. Since there are four turns of the cycle, the total number of reduced dinucleotides produced would be 4 FADH2 and 12 NADH.

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  • 39. 

    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
    In each turn of the citric acid cycle, one ATP is produced through substrate-level phosphorylation. Two CO2 molecules are released as byproducts. Three NADH molecules are produced through redox reactions, and one FADH2 molecule is also produced. Since the question asks for the products after three turns of the cycle, we multiply each of the quantities by three. Therefore, the correct answer is 3 ATP, 6 CO2, 9 NADH, and 3 FADH2.

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  • 40. 

    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 entry point for fatty acid metabolism in the citric acid cycle. It combines with oxaloacetate to form citrate, initiating the cycle and allowing for the production of energy through the oxidation of acetyl CoA.

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  • 41. 

    What are the products of the light reactions that are subsequently used by the Calvin cycle?

    • Oxygen and carbon dioxide

    • Carbon dioxide and RuBP

    • Water and carbon

    • Electrons and photons

    • ATP and NADPH

    Correct Answer
    A. ATP and NADPH
    Explanation
    The products of the light reactions, ATP and NADPH, are subsequently used by the Calvin cycle. ATP is a molecule that provides energy for cellular processes, including the synthesis of glucose during the Calvin cycle. NADPH is a molecule that carries high-energy electrons and hydrogen ions, which are also used in the Calvin cycle to convert carbon dioxide into glucose. Therefore, ATP and NADPH are essential for the Calvin cycle to occur and for the production of glucose.

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  • 42. 

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

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

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

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

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

    • The active site creates a microenvironment ideal for the reaction.

    Correct Answer
    A. The binding of the substrate changes the shape of the enzyme's active site.
    Explanation
    The induced fit hypothesis of enzyme catalysis suggests that the binding of the substrate causes a conformational change in the enzyme's active site. This change in shape allows for a better fit between the enzyme and the substrate, enhancing the catalytic activity. This explanation aligns with the given correct answer that states "The binding of the substrate changes the shape of the enzyme's active site."

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  • 43. 

    During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesis of the water come from?

    • Carbon dioxide (CO2)

    • Glucose (C6H12O6)

    • Molecular oxygen (O2)

    • Pyruvate (C3H3O3–)

    • Lactate (C3H5O3–-)

    Correct Answer
    A. Molecular oxygen (O2)
    Explanation
    During oxidative phosphorylation, H2O is formed through the process of electron transport chain. The electrons that are transferred through the electron transport chain ultimately combine with molecular oxygen (O2) to form water (H2O). This occurs in the final step of the electron transport chain, where oxygen acts as the final electron acceptor and is reduced to form water. Therefore, the oxygen for the synthesis of water during oxidative phosphorylation comes from molecular oxygen (O2).

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  • 44. 

    Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?

    • Glycolysis

    • Fermentation

    • Oxidation of pyruvate to acetyl CoA

    • Citric acid cycle

    • Oxidative phosphorylation (chemiosmosis)

    Correct Answer
    A. Oxidative phosphorylation (chemiosmosis)
    Explanation
    Oxidative phosphorylation (chemiosmosis) produces the most ATP when glucose is completely oxidized to carbon dioxide and water. This process occurs in the mitochondria and involves the electron transport chain and ATP synthase. During oxidative phosphorylation, electrons from NADH and FADH2 are transferred along the electron transport chain, creating a proton gradient across the inner mitochondrial membrane. This gradient drives the synthesis of ATP by ATP synthase. Overall, oxidative phosphorylation produces a total of 36-38 ATP molecules per glucose molecule, making it the most efficient process for ATP production.

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  • 45. 

    In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from

    • The stroma to the photosystem II.

    • The matrix to the stroma.

    • The stroma to the thylakoid space.

    • The intermembrane space to the matrix.

    • ATP synthase to NADP+ reductase.

    Correct Answer
    A. The stroma to the thylakoid space.
    Explanation
    In chloroplasts, chemiosmosis is responsible for the translocation of protons from the stroma to the thylakoid space. This process occurs during photosynthesis and is essential for the generation of ATP. The movement of protons creates an electrochemical gradient, which drives the synthesis of ATP by ATP synthase. This gradient is established by the transfer of electrons through the electron transport chain in the thylakoid membrane. Therefore, the correct answer is "the stroma to the thylakoid space."

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  • 46. 

    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. This process does not require oxygen and is common to both aerobic and anaerobic organisms. The cytosol, which is the liquid component of the cytoplasm, provides the necessary environment and enzymes for glycolysis to take place. Therefore, the correct answer is cytosol.

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  • 47. 

    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 to anabolic pathways. This process involves the use of energy released from the breakdown of molecules in catabolic pathways to drive the synthesis of molecules in anabolic pathways. Energy coupling is essential for the overall functioning and maintenance of cells, as it allows for the conversion and utilization of energy in different forms to support various cellular processes.

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  • 48. 

    The active site of an enzyme is the region that

    • Binds allosteric regulators of the enzyme.

    • Is involved in the catalytic reaction of the enzyme.

    • Binds the products of the catalytic reaction.

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

    • Both A and B

    Correct Answer
    A. 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 it is the specific location where the substrate binds and the chemical reaction takes place. The active site typically has a specific shape and chemical properties that allow it to interact with the substrate and facilitate the conversion of the substrate into product. The binding of allosteric regulators, products of the catalytic reaction, and the inhibition by coenzymes or cofactors may occur at other regions of the enzyme, but they are not directly related to the catalytic reaction itself.

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  • 49. 

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

    • 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.

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

    • A and B only

    • A, B, and C

    Correct Answer
    A. A and B only
    Explanation
    As temperature decreases, the kinetic energy of the molecules decreases, resulting in fewer substrates having sufficient energy to overcome the activation energy barrier. This is explained by option A. Additionally, the motion in the active site of the enzyme is slowed down at lower temperatures, which affects the catalysis of the enzyme. This is explained by option B. Therefore, the correct answer is A and B only.

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  • Current Version
  • Mar 21, 2023
    Quiz Edited by
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  • Nov 30, 2008
    Quiz Created by
    Brownie2007

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