Key Concepts:
• An organism's metabolism transforms matter and energy, subject to the laws of thermodynamics.
• The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously.
• ATP powers cellular work by coupling exergonic reactions to endergonic reactions.
• Enzymes speed up metabolic reactions by lowering energy barriers.
• Regulation of enzyme activity helps control metabolism.
Terms : Hide Images
| 1783889182 | Activation Energy | the amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation | 0 | |
| 1783889183 | Active Site | the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs | 1 | |
| 1785813099 | Adenosine Triphosphate | see ATP | 2 | |
| 1785813100 | Allosteric Regulation | the binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site | 3 | |
| 1785813101 | Anabolic Pathway | a metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules | 4 | |
| 1785813102 | ATP (Adenosine Triphosphate) | an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed; this energy is used to drive endergonic reactions in cells | 5 | |
| 1785813103 | Catabolic Pathway | a metabolic pathway that releases energy by breaking down complex molecules to simpler molecules | 6 | |
| 1785813104 | Catalyst | a chemical agent that selectively increases the rate of a reaction without being consumed by the reaction | 7 | |
| 1785813105 | Chemical Energy | energy available in molecules for release in a chemical reaction; a form of potential energy | 8 | |
| 1785813106 | Coenzyme | an organic molecule serving as a cofactor; most vitamins function as coenzymes in metabolic reactions | 9 | |
| 1785813107 | Cofactor | any nonprotein molecule or ion that is required for the proper functioning of an enzyme; cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis | 10 | |
| 1785813108 | Competitive Inhibitor | a substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics | 11 | |
| 1785813109 | Cooperativity | a kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits | 12 | |
| 1785813110 | Endergonic Reaction | a nonspontaneous chemical reaction in which free energy is absorbed from the surroundings | 13 | |
| 1785813111 | Energy | the capacity to cause change, especially to do work (to move matter against an opposing force) | 14 | |
| 1785813112 | Energy Coupling | in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction | 15 | |
| 1785813113 | Entropy | a measure of disorder, or randomness | 16 | |
| 1785813114 | Enzyme | a macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction; most enzymes are proteins | 17 | |
| 1785813115 | Exergonic Reaction | a spontaneous chemical reaction in which there is a net release of free energy | 18 | |
| 1785813116 | Feedback Inhibition | a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway | 19 | |
| 1785813117 | First Law of Thermodynamics | the principle of conservation of energy: energy can be transferred and transformed, but it cannot be created or destroyed | 20 | |
| 1785813118 | Free Energy | the portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system; the change in free energy of a system (ΔG) is calculated by the equation ΔG = ΔH − TΔS, where ΔH is the change in enthalpy (in biological systems, equivalent to total energy), ΔT is the absolute temperature, and ΔS is the change in entropy | 21 | |
| 1785813119 | Heat | thermal energy in transfer from one body of matter to another | 22 | |
| 1785813120 | Induced Fit | caused by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate | 23 | |
| 1785813121 | Kinetic Energy | the energy associated with the relative motion of objects; moving matter can perform work by imparting motion to other matter | 24 | |
| 1785813122 | Metabolic Pathway | a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway) | 25 | |
| 1785813123 | Metabolism | the totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism | 26 | |
| 1785813124 | Noncompetitive Inhibitor | a substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product | 27 | |
| 1785813125 | Phosphorylated Intermediate | a molecule (often a reactant) with a phosphate group covalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule | 28 | |
| 1785813126 | Potential Energy | the energy that matter possesses as a result of its location or spatial arrangement (structure) | 29 | |
| 1785813127 | Second Law of Thermodynamics | the principle stating that every energy transfer or transformation increases the entropy of the universe; usable forms of energy are at least partly converted to heat | 30 | |
| 1785813128 | Spontaneous Process | a process that occurs without an overall input of energy; a process that is energetically favorable | 31 | |
| 1785813129 | Substrate | the reactant on which an enzyme works | 32 | |
| 1785813130 | Thermal Energy | kinetic energy due to the random motion of atoms and molecules; energy in its most random form; also see heat | 33 | |
| 1785813131 | Thermodynamics | the study of energy transformations that occur in a collection of matter; see also first law of thermodynamics and second law of thermodynamics | 34 | |
| 1788421972 | Which of the following correctly states the relationship between anabolic and catabolic pathways? a. Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways b. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways c. The flow of energy between catabolic and anabolic pathways is reversible d. Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules e. Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways | Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways The synthesis of complex molecules in anabolic pathways requires an input of energy from catabolic pathways. | 35 | |
| 1788421973 | Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description? a. The metabolism of an organism is isolated from its surroundings b. Heat produced by the organism is conserved in the organism and not lost to the environment c. Organisms acquire energy from, and lose energy to, their surroundings d. Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy e. All of the listed responses are correct. | Organisms acquire energy from, and lose energy to, their surroundings Open systems are those in which energy and materials can be exchanged between the system and its surroundings. | 36 | |
| 1788421974 | Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics? a. The process of photosynthesis produces energy that the plant uses to grow b. Growth of the crops must occur spontaneously c. The entropy of the universe must decrease to account for the increased entropy associated with plant growth d. To obey the first law, the crops must represent an open system e. All of the listed responses are correct | To obey the first law, the crops must represent an open system The first law states that energy cannot be created. The growth of plants stores much energy in the body of the plant. That energy must have been obtained from the plant's environment; thus, the plant must be an open system. | 37 | |
| 1788421975 | Which of the following states the relevance of the first law of thermodynamics to biology? a. Energy is destroyed as glucose is broken down during cellular respiration b. Photosynthetic organisms produce energy in sugars from sunlight c. Living organisms must increase the entropy of their surroundings d. Energy can be freely transformed among different forms as long as the total energy is conserved e. Because living things consume energy, the total energy of the universe is constantly decreasing | Energy can be freely transformed among different forms as long as the total energy is conserved The first law of thermodynamics states that energy can be transformed but can be neither created nor destroyed. | 38 | |
| 1788421976 | Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? a. The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water b. All types of cellular respiration produce ATP c. Cellular respiration releases some energy as heat d. The first and second choices are correct e. The first, second, and third choices are correct | The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water The second law of thermodynamics states that every energy transformation makes the universe more disordered—carbon dioxide and water are more disordered than glucose. | 39 | |
| 1788421977 | According to the second law of thermodynamics, which of the following is true? a. The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists b. The entropy of the universe is constantly decreasing c. All reactions produce some heat d. Energy conversions increase the order in the universe e. The total amount of energy in the universe is constant | The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists The second law of thermodynamics demands that total entropy increase with any reaction. | 40 | |
| 1788421978 | If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? a. The entropy of the organism's environment must also be decreasing b. The first law of thermodynamics is being violated c. In this situation, the second law of thermodynamics must not apply d. Heat is being used by the organism as a source of energy e. Energy input into the organism must be occurring to drive the decrease in entropy | Energy input into the organism must be occurring to drive the decrease in entropy If the entropy is decreasing, this would tend to make the free energy change associated with this positive. Thus, an input of energy would be required to make this decrease in entropy occur. | 41 | |
| 1788421979 | Which of the following has the most free energy per molecule? a. a cholesterol molecule b. a fatty acid molecule c. a sugar molecule d. an amino acid molecule e. a starch molecule | a starch molecule Starch is a large polymer of sugar and thus contains many covalent bonds. | 42 | |
| 1788421980 | Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous? a. ΔS b. TΔS c. ΔH d. ΔG e. All of these values reveal the direction in which a reaction will go | ΔG In any spontaneous process, the free energy of a system decreases. The change in free energy equals the change in total energy minus the change in entropy times the temperature. | 43 | |
| 1788421981 | If, during a process, the system becomes more ordered, then __________. a. ΔG is positive b. ΔG is negative c. ΔH is negative d. ΔS is negative e. ΔH is positive | ΔS is negative In an endergonic reaction, in which order is increased, the change in entropy, symbolized by ΔS, is negative. | 44 | |
| 1788421982 | When one molecule is broken down into six component molecules, which of the following will always be true? a. ΔS is negative b. ΔS is positive c. ΔG is positive d. An input of free energy is needed e. ΔH is negative | ΔS is positive The large increase in disorder associated with this reaction means that entropy (ΔS) increases. | 45 | |
| 1788421983 | From the equation ΔG = ΔH - TΔS it is clear that __________. a. a decrease in the system's total energy will increase the probability of spontaneous change b. increasing the entropy of a system will increase the probability of spontaneous change c. increasing the temperature of a system will increase the probability of spontaneous change d. a decrease in the system's total energy will increase the probability of spontaneous change, and increasing the entropy of a system will increase the probability of spontaneous change e. a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change | a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change This is the best response. | 46 | |
| 1788421984 | An exergonic (spontaneous) reaction is a chemical reaction that __________. a. occurs only when an enzyme or other catalyst is present b. cannot occur outside of a living cell c. releases energy when proceeding in the forward direction d. is common in anabolic pathways e. leads to a decrease in the entropy of the universe | releases energy when proceeding in the forward direction Exergonic reactions proceed with a net release of free energy, and they occur spontaneously. | 47 | |
| 1788421985 | Which of the following reactions would be endergonic? a. HCl → H+ + Cl- b. glucose + fructose → sucrose c. ATP → ADP + Pi d. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O e. All of the listed responses are correct | glucose + fructose → sucrose In this case, the product is more complex (lower entropy) than the reactants, and like many anabolic reactions, this one requires an input of energy. | 48 | |
| 1788421986 | Molecules A and B contain 110 kcal/mol of free energy, and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded? a. A and B will be converted to C and D with a net release of energy b. The conversion of A and B to C and D is spontaneous c. The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants d. The entropy in the products, C and D, is higher than in the reactants, A and B e. The conversion of A and B to C and D is exergonic; the products are less organized than the reactants | The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants | 49 | |
| 1788421987 | Which of the following determines the sign of ΔG for a reaction? a. the free energy of the products b. the enzyme catalyzing the reaction's having a high affinity (strength of binding) for the reactants c. the free energy of the reactants d. the enzyme catalyzing the reaction's having a low affinity for the products e. the free energy of the reactants and the free energy of the products | the free energy of the reactants and the free energy of the products By subtracting the free energy of the reactants from the free energy of the products, the ΔG can be calculated and the difference in these values determines the sign of the difference. | 50 | |
| 1788421988 | Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium? a. the continuous removal of the products of a pathway to be used in other reactions b. an input of free energy from outside the pathway c. an input of heat from the environment d. The first and second listed responses are correct e. The first, second, and third listed responses are correct | The first and second listed responses are correct Pathways can be displaced from equilibrium either by adding free energy or by removal of the products of the pathway by other reactions. | 51 | |
| 1788421989 | The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients? a. the beating of cilia b. proton movement against a gradient of protons c. facilitated diffusion d. the chemical synthesis of ATP e. chromosome movement on microtubules | proton movement against a gradient of protons Protein pumps that hydrolyze ATP can generate electrochemical gradients. | 52 | |
| 1788421990 | In general, the hydrolysis of ATP drives cellular work by __________. a. acting as a catalyst b. releasing heat c. changing to ADP and phosphate d. lowering the activation energy of the reaction e. releasing free energy that can be coupled to other reactions | releasing free energy that can be coupled to other reactions With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to endergonic processes. | 53 | |
| 1788421991 | Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell AGAINST the ion's concentration gradient? a. This is an example of energy coupling b. Both ATP hydrolysis and active transport are spontaneous because they result in an increase in entropy of the system c. The hydrolysis of ATP is endergonic, and the active transport is exergonic d. Neither ATP hydrolysis nor active transport is spontaneous e. ATP is acting as a transport protein to facilitate the movement of the ion across the plasma membrane | This is an example of energy coupling The free energy released from the hydrolysis of ATP is coupled to the energy-requiring active transport of the ion across a membrane. | 54 | |
| 1788421992 | Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because __________. a. the bonds between the phosphate groups are unusually strong and breaking them releases free energy b. the valence electrons in the phosphorus atom have less energy on average than those of other atoms c. they are hydrogen bonds, which are only about 10% as strong as covalent bonds d. the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP e. the phosphate groups are polar and are attracted to the water in the cell's interior | the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP Negative charges repel each other. Loss of the terminal phosphate removes some of the repulsion. | 55 | |
| 1788421993 | When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations? a. Cells are less efficient at energy metabolism than reactions that are optimized in a test tube b. In the cell, the hydrolysis of ATP is coupled to other endergonic reactions c. Cells have the ability to store heat; this cannot happen in a test tube d. The amount of heat released by a reaction has nothing to do with the free energy change of the reaction e. In cells, ATP is hydrolyzed to ADP and Pi, but in the test tube it is hydrolyzed to carbon dioxide and water | In the cell, the hydrolysis of ATP is coupled to other endergonic reactions The coupling of ATP to other endergonic processes in cells means that less of the free energy is released as heat. When ATP is hydrolyzed without this coupling, all of the energy is released as heat. | 56 | |
| 1788421994 | Which of the following best characterizes the role of ATP in cellular metabolism? a. The charge on the phosphate group of ATP tends to make the molecule very water-soluble b. The ΔG associated with its hydrolysis is positive c. The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate d. The release of free energy during the hydrolysis of ATP heats the surrounding environment e. It is catabolized to carbon dioxide and water | The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate This is one way a cell can use an exergonic reaction to drive an endergonic reaction. | 57 | |
| 1788421995 | The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways? a. the conversion of glucose + fructose to make sucrose b. the hydrolysis of ATP c. the active transport of a phosphate ion into the cell d. the contraction of a muscle cell e. the formation of ATP from ADP + Pi | the hydrolysis of ATP With the help of specific enzymes, the cell is able to couple the energy of ATP hydrolysis directly to endergonic processes by transferring a phosphate group from ATP to some other molecule, such as glucose. | 58 | |
| 1788421996 | A chemical reaction is designated as exergonic rather than endergonic when __________. a. activation energy is required b. the products are less complex than the reactants c. it absorbs more energy d. the potential energy of the products is less than the potential energy of the reactants e. activation energy exceeds net energy release | the potential energy of the products is less than the potential energy of the reactants If a reaction is exergonic, the formation of new bonds releases more energy than was invested in breaking the old bonds. | 59 | |
| 1788421997 | What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction? a. The sign determines whether the reaction is spontaneous, and the magnitude determines the speed b. Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction c. The more negative the ΔG, the faster the reaction is d. The sign does not matter, but the larger the magnitude of ΔG, the faster the reaction e. The sign does not matter, but the smaller the magnitude of ΔG, the faster the reaction | Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction The speed of a reaction is determined by the activation energy barrier of the reaction and the temperature (which determines how many reactants have the energy to overcome the barrier). | 60 | |
| 1788421998 | How do enzymes lower activation energy? a. by increasing reactivity of products b. by locally concentrating the reactants c. by harnessing heat energy to drive the breakage of bonds between atoms d. The first two responses are correct e. The second and third choices are correct | by locally concentrating the reactants One of the ways enzymes work is to increase the concentrations of reactants at a single place. | 61 | |
| 1788421999 | Which of the following statements about enzymes is/are true? a. Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme b. Enzymes increase the rate of a reaction by raising the activation energy for reactions c. The more heat that is added to a reaction, the faster the enzymes will function d. Enzymes speed up the rate of the reaction without changing the ΔG for the reaction e. All of the listed responses are correct | Enzymes speed up the rate of the reaction without changing the ΔG for the reaction Enzymes speed up reactions by lowering the activation energy barrier for the reaction. Enzymes cannot change the DG for the reaction. | 62 | |
| 1788422000 | Which of the following statements about enzyme function is correct? a. Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the activation energy b. Enzymes can greatly speed up reactions, but they cannot change the activation energy because they cannot change the net energy output c. Enzymes can change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the net energy output d. Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output e. None of the listed responses is correct | Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output Enzymes lower the activation energy barrier of a reaction but do not change the free energy of the products. | 63 | |
| 1788422001 | A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________. a. the enzyme was denatured b. the cofactors required by the enzyme system lack the thermal energy required to activate the enzyme c. the substrate becomes a competitive inhibitor at lower temperature d. there is too little activation energy available e. the hydrogen bonds that define the structure of the enzyme's active site are unstable | there is too little activation energy available The environment usually supplies activation energy in the form of heat. The lower the temperature, the less energy that is available to overcome the activation energy barrier. | 64 | |
| 1788422002 | Which of the following statements about enzymes is INCORRECT? a. An enzyme lowers the activation energy of a chemical reaction b. Enzymes can be used to accelerate both anabolic and catabolic reactions c. An enzyme is consumed during the reaction it catalyzes d. An enzyme is very specific in terms of the substrate to which it binds e. Most enzymes are proteins | An enzyme is consumed during the reaction it catalyzes If enzymes were consumed during the reaction they catalyzed, they would not be able to act as a catalyst. This statement is incorrect. | 65 | |
| 1788422003 | Which of the following statements about the active site of an enzyme is correct? a. The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits b. The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme c. The active site has a fixed structure (shape) d. The structure of the active site is not affected by changes in temperature e. Coenzymes are rarely found in the active site of an enzyme | The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits Only a restricted region of an enzyme molecule (the active site) binds to the substrate. Usually, the active site is formed by only a few of the amino acids, with the rest of the protein molecule providing a framework that reinforces the configuration of the active site. | 66 | |
| 1788422004 | What is meant by the "induced fit" of an enzyme? a. The presence of the substrate in solution induces the enzyme to slightly change its structure b. The shape of the active site is nearly perfect for specifically binding the enzyme's substrate or substrates c. The substrate can be altered so that it is induced to fit into the enzyme's active site d. The enzyme changes its shape slightly as the substrate binds to it e. The enzyme structure is altered so that it can be induced to fit many different types of substrate | The enzyme changes its shape slightly as the substrate binds to it The enzyme changes slightly to bind to the substrate and catalyze the reaction. | 67 | |
| 1788422005 | Which of the following statements correctly describe(s) the role or roles of heat in biological reactions? a. Heat from the environment is necessary for substrates to get over the activation energy barrier b. The kinetic energy of the substrates is increased as the amount of heat in the system is increased c. Increasing the amount of heat in a system will always increase the rate of enzyme-catalyzed reactions d. The first and second choices are correct e. The second and third choices are correct | The first and second choices are correct As the heat energy in a system increases, so does the kinetic energy of the reactants. As the kinetic energy of the reactants increases, the reactants are more likely to interact (with each other directly, or with the active site of an enzyme). Subsequently, the reaction rate would increase. | 68 | |
| 1788422006 | Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions? a. an increase in concentration of enzyme b. increasing the temperature by a few degrees c. increasing the substrate concentration d. The first and second listed responses are correct e. The first, second, and third listed responses are correct | The first and second listed responses are correct Either increasing the enzyme concentration or slightly increasing the temperature will increase the rate of product formation. | 69 | |
| 1788422007 | Which of the following environments or actions would NOT affect the rate of an enzyme reaction? a. cooling the enzyme b. substrate concentration c. heating the enzyme d. pH e. None of the listed responses is correct | None of the listed responses is correct Changes in temperature, substrate concentration, and pH are all likely to affect enzyme activity. | 70 | |
| 1788422008 | Enzyme activity is affected by pH because __________. a. most substrates do not function well at high or low pH b. low pH will denature all enzymes c. changes in pH can cause loss of cofactors from the enzyme d. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier e. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site | high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site Each enzyme has an optimal pH at which it is most active, and variations in pH can alter the enzyme's structure, changing activity. | 71 | |
| 1788422009 | Which of these statements about enzyme inhibitors is true? a. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback b. A competitive inhibitor binds to the enzyme at a place that is separate from the active site c. The action of competitive inhibitors may be reversible or irreversible d. Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory e. A noncompetitive inhibitor does not change the shape of the active site | The action of competitive inhibitors may be reversible or irreversible Competitive inhibitors that bind covalently to the enzyme would be irreversible, and those that bind weakly would be reversible. | 72 | |
| 1788422010 | Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation? a. The active site must have the wrong configuration to permit succinylcholine binding b. The presence of succinylcholine changes the conditions in the solution, resulting in a denaturation of the enzyme c. Succinylcholine must be an allosteric regulator for this enzyme d. Succinylcholine must be a noncompetitive inhibitor e. Succinylcholine must be a competitive inhibitor with acetylcholine | Succinylcholine must be a competitive inhibitor with acetylcholine Competitive inhibition occurs when a molecule mimics the substrate by competing with it at the active site. | 73 | |
| 1788422011 | The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of __________. a. allosteric activation b. competitive inhibition c. feedback inhibition d. cooperativity e. noncompetitive inhibition | allosteric activation The molecule in this example would be termed an allosteric activator. | 74 | |
| 1788422012 | Which of the following statements about allosteric proteins is/are true? a. They are acted on by inhibitors b. They exist in active and inactive conformations c. They are sensitive to environmental conditions d. All of the first three listed responses are correct e. None of the first three listed responses is correct | All of the first three listed responses are correct | 75 | |
| 1788422013 | The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs? a. The allosteric inhibitor lowers the temperature of the active site b. The allosteric inhibitor binds to the substrate and prevents it from binding at the active site c. The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site d. The allosteric inhibitor binds to the active site, preventing the substrate from binding e. The allosteric inhibitor causes free energy change of the reaction to increase | The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site In general, any allosteric regulator functions by changing the structure of the enzyme to change the ability of the active site to bind the substrate. | 76 | |
| 1788422014 | Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true? a. High levels of ADP result in allosteric inhibition of anabolic pathways b. High levels of ATP result in allosteric activation of anabolic pathways c. High levels of ADP result in allosteric inhibition of catabolic pathways d. High levels of ATP result in allosteric activation of catabolic pathways e. High levels of ADP result in allosteric activation of catabolic pathways | High levels of ATP result in allosteric activation of catabolic pathways | 77 | |
| 1788422015 | Choose the pair of terms that correctly completes this sentence. Catabolism is to anabolism as _____ is to _____. a. exergonic; endergonic b. work; energy c. exergonic; spontaneous d. entropy; enthalpy e. free energy; entropy | exergonic; endergonic | 78 | |
| 1788422016 | Most cells cannot harness heat to perform work because a. heat is not a form of energy b. heat must remain constant during work c. cells do not have much heat; they are relatively cool d. heat can never be used to do work e. temperature is usually uniform throughout a cell | temperature is usually uniform throughout a cell | 79 | |
| 1788422017 | Which of the following metabolic processes can occur without a net influx of energy from some other process? a. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O b. 6 CO2 + 6 H2O → C6H12O6 + 6 O2 c. amino acids → protein d. ADP + i → ATP + H2O e. glucose + fructose → sucrose | C6H12O6 + 6 O2 → 6 CO2 + 6 H2O | 80 | |
| 1788422018 | If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add a noncompetitive inhibitor b. add an allosteric inhibitor c. add more substrate d. add more of the enzyme e. heat the solution to 90°C | add more of the enzyme | 81 | |
| 1788422019 | Some bacteria are metabolically active in hot springs because a. they are able to maintain a lower internal temperature b. their enzymes are completely insensitive to temperature c. high temperatures make catalysis unnecessary d. they use molecules other than proteins or RNAs as their main catalysts e. their enzymes have high optimal temperatures | their enzymes have high optimal temperatures | 82 | |
| 1788422020 | If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur? a. Additional product will be formed b. Additional substrate will be formed c. The free energy of the system will change d. Nothing; the reaction will stay at equilibrium e. The reaction will change from endergonic to exergonic | Nothing; the reaction will stay at equilibrium | 83 | |
| 1788422021 | Which of the following is changed by the presence of an enzyme in a reaction? a. the G value for the products b. the magnitude of ΔG c. the sign of ΔG d. the activation energy e. the G value for the reactants | the activation energy | 84 | |
| 1788422022 | It is possible to transform kinetic energy into potential energy and visa versa. a. True b. False | True | 85 | |
| 1788422023 | The study of energy flow through a living organism defines... a. metabolism b. catabolism c. anabolism d. bioernergetics e. none of the above are correct | bioernergetics | 86 | |
| 1788422024 | Living organisms would be examples of isolated systems. a. True b. False | False | 87 | |
| 1788422025 | Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing... a. chemical energy into kinetic energy b. chemical energy into potential energy c. kinetic energy into potential energy d. kinetic energy into chemical energy e. None of the choices are correct | chemical energy into kinetic energy | 88 | |
| 1788422026 | Which of the following is an example of potential rather than kinetic energy? a. a boy mowing grass b. water rushing over Niagara Falls c. a firefly using light flashes to attract a mate d. a food molecule made up of energy-rich macromolecules e. an insect foraging for food | a food molecule made up of energy-rich macromolecules | 89 | |
| 1788422027 | Which of the following is (are) true for anabolic pathways? a. They do not depend on enzymes b. They are usually highly spontaneous chemical reactions c. They consume energy to build up polymers from monomers d. They release energy as they degrade polymers to monomers | They consume energy to build up polymers from monomers | 90 | |
| 1788422044 | 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. curve 1 b. curve 2 c. curve 3 d. curve 4 e. curve 5 | curve 3 |  | 91 |
| 1788422028 | 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 | Add a catalyst | 92 | |
| 1788422029 | Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? a. denaturization of the enzyme b. allosteric inhibition c. competitive inhibition d. saturation of the enzyme activity e. insufficient cofactors | competitive inhibition | 93 | |
| 1788422045 | Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid? a. curve 1 b. curve 2 c. curve 3 d. curve 4 e. curve 5 | curve 4 | | 94 |
| 1788422030 | Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of ... a. competitive inhibition b. noncompetitive inhibition c. feedback inhibition d. positive feedback e. irreversible inhibition | feedback inhibition | 95 | |
| 1788422031 | If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur? a. Additional product would be formed b. Additional substrate would be formed c. The reaction would change from endergonic to exergonic d. The free energy of the system would change e. Nothing; the reaction would stay at equilibrium | Nothing; the reaction would stay at equilibrium | 96 | |
| 1788422046 | Which of the following is the most correct interpretation of the figure? a. Inorganic phosphate is created from organic phosphate b. Energy from catabolism can be used directly for performing cellular work c. ADP + Pi are a set of molecules that store energy for catabolism d. ATP is a molecule that acts as an intermediary to store energy for cellular work e. Pi acts as a shuttle molecule to move energy from ATP to ADP | ATP is a molecule that acts as an intermediary to store energy for cellular work |  | 97 |
| 1788422032 | Some bacteria are metabolically active in hot springs because a. they are able to maintain a cooler internal temperature b. high temperatures make catalysis unnecessary c. their enzymes have high optimal temperatures d. their enzymes are completely insensitive to temperature e. they use molecules other than proteins or RNAs as their main catalysts | their enzymes have high optimal temperatures | 98 | |
| 1788422033 | If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add more of the enzyme b. heat the solution to 90°C c. add more substrate d. add an allosteric inhibitor e. add a noncompetitive inhibitor | add more of the enzyme | 99 | |
| 1788422034 | An exergonic (spontaneous) reaction is a chemical reaction that _____. a. occurs only when an enzyme or other catalyst is present b. cannot occur outside of a living cell c. releases energy when proceeding in the forward direction d. is common in anabolic pathways e. leads to a decrease in the entropy of the universe | releases energy when proceeding in the forward direction | 100 | |
| 1788422035 | Which of the following is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP? a. mechanical work, such as the beating of cilia b. transport work, such as the active transport of an ion into a cell c. chemical work, such as the synthesis of new protein d. all of the above e. none of the above | all of the above | 101 | |
| 1788422036 | Which of the following environments or actions affect(s) the rate of an enzyme reaction? a. heating the enzyme b. cooling the enzyme c. substrate concentration d. pH e. all of the above | all of the above | 102 | |
| 1788422037 | The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of ___. a. feedback inhibition b. competitive inhibition c. allosteric regulation d. non-competitive inhibition e. cooperativity | allosteric regulation | 103 | |
| 1788422038 | Enzyme activity is affected by pH because ___. a. most substrates don't function well at high or low pH b. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site c. low pH will denature all enzymes d. changes in pH can cause loss of cofactors from the enzyme e. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier | high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site | 104 | |
| 1788422039 | Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?( a. The metabolism of an organism is isolated from its surroundings b. Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy c. Organisms acquire energy from their surroundings d. Heat produced by the organism is conserved in the organism and not lost to the environment e. all of the above | Organisms acquire energy from their surroundings. | 105 | |
| 1788422040 | Which of the following statements about enzymes is correct? a. Most enzymes are proteins b. An enzyme is not consumed by the catalytic process c. An enzyme is very specific in terms of which substrate it binds to d. An enzyme lowers the activation energy of a chemical reaction e. all of the above | all of the above | 106 | |
| 1788422041 | The mechanism of enzyme action is _____ . a. providing energy to speed up the rate of the reaction b. lowering the energy of activation for a reaction c. changing the direction of thermodynamic equilibrium d. changing endergonic into exergonic reactions e. lowering the free energy change of a reaction | lowering the energy of activation for a reaction | 107 | |
| 1788422042 | Which of the following reactions would be endergonic? a. HCl » H+ + Cl- b. C6H12O6 + 6 O2 » 6 CO2 + 6 H2O c. ATP » ADP + Pi d. glucose + fructose » sucrose e. all of the above | glucose + fructose » sucrose | 108 | |
| 1788422043 | Which is the most abundant form of energy in a cell? a. chemical and electrical gradients b. mechanical energy c. heat d. kinetic energy e. chemical energy | chemical energy | 109 |
