CH 10
In thermodynamic studies, energy changes are analyzed in a collection of matter called a __________. All other matter in the universe is called the ___________.
system; surroundings
A molecule that binds to an enzyme at a location other than the active site and thereby alters the enzyme's shape, making it inactive or less active is a(n) _________ inhibitor.
Noncompetitive
_________ reactions build new organic molecules from smaller inorganic and organic compounds
Anabolic
For the reaction A + B → C + D, the equilibrium constant (Keq) is expressed as ________. A) [A][B]/[C][D] B) [C][D]/[A][B] C) [A][D]/[B][C] D) [B][C]/[A][D]
B) [C][D]/[A][B]
The amount of heat energy needed to raise 1 gram of water from 14.5 C to 15.5 C is called a(n) ________. A) joule B) calorie C) erg D) thermal unit
B) calorie
Catalytic proteins are known as ________ whereas catalytic RNA molecules are known as ________. A) ribozymes; enzymes B) enzymes; ribozymes C) enzymes; catalozymes D) catalozymes; ribozymes
B) enzymes; ribozymes
When the end product of a pathway inhibits catalysis of the first step of that pathway, this phenomenon is called ________. A) reversible covalent modification B) feedback inhibition C) metabolic channeling D) noncompetitive inhibition
B) feedback inhibition
If all available enzyme molecules are binding substrate and converting it to product as rapidly as possible, the reaction is said to be proceeding at ________ velocity. A) terminal B) maximal C) optimal D) infinite
B) maximal
The energy required to bring the substrates of a reaction together in the correct way to reach the transition state is called ________. A) free energy B) activation energy C) enthalpy D) entropy
B) Activation Energy
The substrate of an enzyme binds at the ________. A) affinity site B) active site C) determinative site D) reaction site
B) Active Site
A(n) ________ increases the rate of a reaction without being permanently altered by the reaction. A) catalyzer B) catalyst C) reactant D) rate increaser
B) Catalyst
A nonprotein component of an enzyme that is loosely attached to the protein component is referred to as a(n) ________. A) apoenzyme B) coenzyme C) holoenzyme D) prosthetic group
B) Coenzyme
A chemical reaction that requires an input of energy in order to proceed is ________. A) exergonic B) endergonic C) impossible D) None of the choices are correct.
B) Endergonic
_________ is the total energy change that accompanies a chemical reaction. A) Entropy B) Enthalpy C) Free energy D) Synergy
B) Enthalpy
As the difference in reduction potential between a redox pair increases, the amount of free energy made available ________. A) decreases B) increases C) remains the same D) cannot be determined
B) Increases
In metabolic channeling, the regulation of metabolic pathways is controlled by the ________ of metabolites and enzymes involved in the pathway. A) amount B) location C) activity D) All of the choices are correct.
B) Location
Consider the following two half reactions:NAD+ + H+ +2e−→NADH Eo(volts)=−0.32 Pyruvate− + 2H+ + 2e− → lactate 2− Eo(volts) = − 0.19 In a redox reaction involving NAD/NADH and pyruvate, ________ will be the electron donor and ________ will be the electron acceptor.A) lactate; pyruvate B) NADH; pyruvate C) NAD+; pyruvate D) pyrvuate; lactate
B) NADH; Pyruvate
The ________ is the electron acceptor in a redox reaction. A) reductant B) oxidant C) enzyme D) product
B) Oxidant
Feedback inhibition, covalent modification, and allosteric regulation are all examples of ________. A) regulation of gene expression B) posttranslational regulation C) metabolic channeling D) compartmentalization
B) Post-translational regulation
The standard reduction potential of a redox reaction is a measure of the tendency of the ________ to ________ electrons. A) reductant; gain B) reductant; lose C) oxidant; gain D) oxidant; lose
B) Reductant; Lose
Cells carry out three major types of work; which of the following involves nutrient uptake and waste elimination? A) Chemical work B) Transport work C) Mechanical work D) None of the choices are correct.
B) Transport work
How does the binding of a regulatory molecule to the allosteric site affect the activity of an enzyme? (Check all that apply.) A) It causes the enzyme to denature and become inactive. B) It may change the affinity of the enzyme for its substrate. C) It may cause the active site to disappear altogether. D) It may change the maximum velocity of the enzyme. E) It may decrease the activity of the enzyme. F) It may increase the activity of the enzyme. G) It may change the shape of the enzyme.
B, D, E, F, G
Which of the following reactions is catalyzed by a ribozyme? A) First reaction in glycolysis (phosphorylation of glucose) B) Attachment of amino acid to transfer RNA C) Peptide bond formation during protein synthesis D) Last step in electron transport chain (reduction of O2 to form H2O)
C) Peptide bond formation during protein synthesis
In allosteric regulation, effector molecules usually bind ________. A) reversibly and covalently B) irreversibly and covalently C) reversibly and noncovalently D) irreversibly and noncovalently
C) Reversibly and noncovalently
Metabolic channeling involves the localization of ________ in different parts of a cell in order to influence the activity of metabolic pathways. A) activators B) repressors C) substrates and enzymes D) inhibitors
C) Substrates and enzymes
The binding of a positive allosteric regulator molecule will ________. A) increase the ability of the substrate to bind to the allosteric site B) decrease the ability of the substrate to bind to the allosteric site C) increase the ability of the substrate to bind to the catalytic site D) decrease the ability of the substrate to bind to the catalytic site
C) increase the ability of the substrate to bind to the catalytic site
Cells must efficiently transfer energy from their energy-trapping systems to the systems actually carrying out work and also used various metabolic processes to replace the energy used in doing work. This is called the ________.
Energy cycle
Enzymes function as catalysts by ________. A) concentrating the substrates together at the active site B) correctly orienting the substrates at the active site C) concentrating the substrates and correctly orienting them at the active site D) None of the choices are correct.
C) Concentrating the substrates and correctly orienting them at the active site
Enzymes catalyze a reaction by ________. A) decreasing the amount of energy released by the reaction B) increasing the amount of energy released by the reaction C) decreasing the activation energy of the reaction D) increasing the activation energy of the reaction
C) Decreasing the activation energy of the reaction
The most specific term usually used to describe a substance in a biological system that increases the rate of a reaction without being permanently changed by the reaction is a(n) ________. A) catalyzer B) reductant C) enzyme D) rate increaser
C) Enzyme
The change in ________ is the amount of energy in a system that is available to do work. A) entropy B) enthalpy C) free energy D) synergy
C) Free Energy
A complete enzyme that consists of a protein component and a nonprotein component is called a(n) ________. A) apoenzyme B) heteroenzyme C) holoenzyme D) multienzyme
C) Holoenzyme
Cells carry out three major types of work. Which of the following involves energy for cell motility and the movement of structures within cells? A) Chemical work B) Transport work C) Mechanical work D) None of the choices are correct
C) Mechanical work
_______ reactions capture energy from the organisms' energy source
Catabolic
A molecules that binds noncovalently to an enzyme-catalyzed reaction are called ___________.
Competitive
Enzymes are usually named based on ________. A) the substrates they act on B) their molecular structure C) the type of reaction they catalyze D) All of the choices are correct. E) the substrates they act on and the type of reaction they catalyze
E) the substrates they act on and the type of reaction they catalyze
Enzyme activity can be controlled by ________. A) allosteric regulation B) covalent modification C) feedback (end product) inhibition D) All of the choices are correct.
D) All of the choices are correct
Which of the following is a reason for metabolic regulation? A) Maintain cell components at appropriate levels B) Conserve materials C) Ensure efficient use of energy stores D) All of the choices are correct.
D) All of the choices are correct
Which of the following is used as an electron carrier by living organisms? A) NAD+ B) NADP+ C) Ubiquinone D) All of the choices are correct.
D) All of the choices are correct
Which of the following is/are true about enzymes? A) Enzymes are catalysts that speed up reactions. B) Enzymes are proteins that can be denatured by changes in pH or temperature. C) Enzymes are highly specific for the substrates they react with and catalyze only one or a limited set of possible reactions with those substrates. D) All of the choices are correct.
D) All of the choices are correct
Consider a biochemical pathway that branches to form two different products. If the end product of one of the branches is present in a large amount, at what point would the pathway be regulated to ensure adequate production of the end product of the alternative pathway while slowing or stopping production of the product already present in excess? A) At the very first step in the entire pathway B) At the last step in the pathway to the product in excess C) At the last step in the pathway to the alternative product still needed D) At the point where the two pathways branch
D) At the point where the two pathways branch
Electron transport molecules that only transfer electrons include ________. A) ubiquinone B) NADP C) FAD D) ferredoxin
D) Ferredoxin
What nucleoside trisphosphate, other than ATP, provides some of the energy for protein synthesis? A) UTP B) TTP C) CTP D) GTP
D) GTP
The nonprotein component of an enzyme that is firmly attached to the protein is called a(n) ________. A) apoenzyme B) coenzyme C) holoenzyme D) prosthetic group
D) Prosthetic group
T/F Enzymes decrease the overall free energy change in a chemical reaction.
FALSE
_________ is the total of all chemical reactions occurring in the cell
Metabolism
The ________ _________ is the substrate concentration needed for an enzyme to achieve half maximal velocity.Michaelis constant (Km)
Michaelis constant (Km)
ATP has a phosphate transfer potential of 30.5, whereas glucose-6-phosphate has a phosphate transfer potential of 13.8. Based on these differences, which of the following will happen? A) ATP will transfer phosphate to glucose-6-phosphate. B) Glucose-6-phosphate will transfer phosphate to ADP forming ATP. C) Phosphates will not be transferred between these molecules. D) ATP will transfer phosphate to phosphoenolpyruvate.
A) ATP will transfer phosphate to glucose-6-phosphate
Which of the following are components of the ATP molecule? (Check all that apply.) A) Adenine B) Ribose C) Deoxyribose D) Three phosphates
A) Adenine B) Ribose D) Three phosphates
If an enzyme consists of a protein component and a nonprotein component, the protein component is referred as the ________. A) apoenzyme B) coenzyme C) holoenzyme D) prosthetic group
A) Apoenzyme
Cells carry out three major types of work; which of the following involves the synthesis of macromolecules as well as the breakdown of substances for their energy? a) Chemical work b) Transport work c) Mechanical work d) None of the choices are correct
A) Chemical work
In the electron transport chain, why do electrons flow in one direction from NADH to O2 rather than the reverse direction, or randomly? A) Electrons flow from NADH to O2 because NADH has the most negative reduction potential and O2 the most positive with electron carriers in between, each becoming more positive to direct the electron flow. B) Electrons flow from NADH to O2 because NADH has the most positive reduction potential and O2 the most negative with electron carriers in between, each becoming more negative to direct the electron flow. C) Electrons flow from NADH to O2 because the change in free energy directs the electron flow from the molecule with the most positive reduction potential to the one with the most negative. D) Electrons flow from NADH to O2 using ATP as a source of energy to drive the flow against their gradient from most negative reduction potential to most positive.
A) Electrons flow from NADH to O2 because NADH has the most negative reduction potential and O2 the most positive with electron carriers in between, each becoming more positive to direct the electron flow.
__________ is a measure of the randomness or disorder of a system. A) Entropy B) Enthalpy C) Free energy D) Synergy
A) Entropy
A reaction that releases energy is ________. A) exergonic B) endergonic C) impossible D) None of the choices are correct.
A) Exergonic
A bacterial biosynthetic pathway synthesizes an amino acid in a series of steps, each catalyzed by a different enzyme. The bacteria is transferred to fresh media where the amino acid is present in abundance. The amino acid binds to a regulatory site on the first enzyme in the pathway, effectively shutting down the entire process. This is an example of ________. A) feedback inhibition B) covalent modification C) metabolic channeling D) gene regulation
A) Feedback inhibition
Based on phosphate transfer potential, which is more likely to happen? A) Phosphoenolpyruvate will transfer phosphate to ADP B) ATP will transfer phosphate to phosphoenolpyruvate C) There will be no phosphate transfer between these molecules
A) Phosphoenolpyruvate will transfer phosphate to ADP
Where is the electron transport chain located in bacterial cells? A) Plasma membrane B) Periplasm C) Mitochondrial inner membrane D) Mitochondrial outer membrane
A) Plasma membrane
The ________ is the electron donor in a redox reaction. A) reductant B) oxidant C) enzyme D) product
A) Reductant
The ________ law of thermodynamics states that energy can be neither created nor destroyed. A) first B) second C) third D) fourth
A) first
Consider a biochemical pathway with five steps that lead to the production of product Q. If there is an abundance of product Q, the most efficient way to slow down the entire pathway would be to regulate ________. A) the first enzyme in the pathway B) the last enzyme in the pathway C) every enzyme in the pathway
A) The first enzyme in the pathway
What nucleoside trisphosphate provides energy for lipid synthesis? A) UTP B) TTP C) CTP D) GTP
A) UTP
In the equation ΔG'o = nF ∙ ΔE'o, ________. A) the greater the difference in standard reduction potentials between the electron donor and electron acceptor, the greater the free energy available to do work B) when the difference in reduction potentials between the electron donor and electron acceptor is small, the yield of free energy is great C) the greater the difference in reduction potentials of the participants of the redox reaction, the smaller the energy yield to the surroundings D) the difference between the reduction potentials of the redox participants is inversely proportional to the change in free energy
A) the greater the difference in standard reduction potentials between the electron donor and electron acceptor, the greater the free energy available to do work
Which three of the following groups are most commonly used to covalently modify an enzyme and its activity? (Check all that apply.) A) Phosphoryl group B) Hydroxyl group C) Methyl group D) Adenyl group
A, C, D
In order for the cell to be able to input energy into necessary endergonic reactions, energy-generating processes such as photosynthesis, fermentation, and respiration are used to produce ___________.
ATP
The energy made available during cell respiration and fermentation is used to make ________, which is then available to provide energy for cellular work.
ATP
In a branched pathway with many end products, an abundance of one of the end products will usually inhibit ________. A) the first step in the set of pathways B) the first committed step in the branch of the pathway leading to the production of that particular product C) the last step before the branch leading to the production of that particular end product D) the last step in the production of that particular product
B) The first committed step in the branch of the pathway leading to the production of that particular product
The ________ law of thermodynamics states that physical and chemical processes occur in such a way that randomness (disorder) increases to a maximum. A) first B) second C) third D) fourth
B) second
Disruption of an enzymes structure with loss of activity caused by extremes of pH, temperature, or other factors is called ___________.
Denaturation
Which strategy can be used for regulation of metabolism? A) Feedback inhibition B) Allosteric regulation C) Regulation of enzyme synthesis D) Covalent modification of enzymes E) All of the choices are correct.
E) All of the choices are correct
In bacterial and archaeal cells, the electron transport chain is located in the ________ whereas in eukaryotic cells, the electron transport chain is located in the ________. A) inner mitochondrial membrane; outer mitochondrial membrane B) plasma membrane; outer mitochondrial membrane C) inner mitochondrial membrane; plasma membrane D) plasma membrane; mitochondrial matrix E) plasma membrane; inner mitochondrial membrane
E) Plasma membrane; Inner mitochondrial membrane
A reaction in which the forward rate is equal to the reverse rate is said to be at __________.
Equilibrium
T/F Enzymes increase the rate of a reaction by increasing molecular motion, thereby providing kinetic energy to drive the reaction.
FALSE
T/F In an ATP molecule, the phosphates are bonded to the adenine ring.
FALSE
T/F One important ribozyme responsible for catalyzing peptide bond formation during protein synthesis, is located in the mitochondria.
FALSE
T/F The Michaelis constant (Km) of an enzyme is the substrate concentration that produces maximum velocity.
FALSE
T/F The electron transport chain is based on the principle that redox couples with more positive reduction potentials will donate electrons to couples with more negative potentials.
FALSE
T/F The most commonly used practical form of energy used in cells is adenosine diphosphate.
FALSE
T/F The numerical value of the free energy change indicates how fast a reaction will reach equilibrium.
FALSE
T/F The regulatory site in an allosteric enzyme is found within the catalytic site.
FALSE
T/F When the amount of enzyme present is held constant, the rate of a reaction will continue to increase as long as the substrate concentration increases.
FALSE
The molecules formed by an enzyme-catalyzed reaction are called _________.
Products
RNA molecules that have catalytic activity are known as ___________.
Ribozymes
Until the discovery of ________, enzymes were the only recognized biological molecules that were catalytic.
Ribozymes
The reacting molecules in an enzyme-catalyzed reaction are called _________.
Substrates
T/F Covalent modification of enzymes most commonly uses phosphoryl, methyl, and adenyl groups.
TRUE
T/F Each enzyme normally has specific pH and temperature optima at which they function best.
TRUE
T/F Energy can be redistributed within a collection of matter (called a system) or can be redistributed between the system and its surroundings
TRUE
T/F Enzyme activity can be greatly affected by the pH and the temperature of the environment in which the enzyme must function.
TRUE
T/F Enzymes increase the rate of a reaction but do not alter equilibrium constants.
TRUE
T/F Isoenzymes are different enzymes that catalyze the same reaction but can be regulated independently of one another.
TRUE
T/F One of the components used during photosynthetic electron transport is ferredoxin, a nonheme iron protein
TRUE
T/F Some endergonic reactions can be made to proceed forward if they are coupled to hydrolysis of one or more of the phosphates of ATP.
TRUE
T/F The equilibrium constant for a redox reaction is called the standard reduction potential
TRUE
__________ is the science that analyzes energy changes in a collection of matter.
Thermodynamics
A complex formed during a reaction that resembles both the substrate and the product is called the ________ state complex.
Transition
A positive allosteric effector will ________ the activity of an enzyme while a negative effector will ________ the activity.
increase; decrease
