Enzyme Principles and Characteristics Quiz
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Questions and Answers

What is the role of enzymes in chemical reactions?

  • Enzymes act as inhibitors of chemical reactions.
  • Enzymes act as biological catalysts, increasing reaction rates by lowering activation barriers. (correct)
  • Enzymes act as reactants in chemical reactions.
  • Enzymes act as energy sources for chemical reactions.

    • What happens in the absence of enzyme catalysis in chemical reactions?

  • Chemical reactions occur without any impact on life sustenance.
  • Chemical reactions occur at a slower rate.
  • Chemical reactions could not occur on a useful time scale, hindering the sustenance of life. (correct)
  • Chemical reactions occur at a faster rate.

    • What is the consequence of excessive activity of an enzyme?

  • It can lead to disease. (correct)
  • It enhances overall health.
  • It has no impact on health.
  • It leads to increased enzyme specificity.

    • Why are measurements of enzyme activities in blood plasma, erythrocytes, or tissue samples important?

    <p>They are important in diagnosis.</p> Signup and view all the answers

    What is a key characteristic of enzyme catalysis?

    <p>Enzymes exhibit a very high degree of specificity.</p> Signup and view all the answers

    Which statement best describes the transition state in a reaction?

    <p>It is the point at which decay to substrate or product are equally likely.</p> Signup and view all the answers

    What is the relationship between equilibrium constant (K′eq) and standard free-energy change (∆G′°)?

    <p>∆G′° = −RT ln K′eq</p> Signup and view all the answers

    What does the activation energy (∆G‡) represent in a reaction?

    <p>The difference between the ground state energy level and the transition state energy level.</p> Signup and view all the answers

    How do catalysts affect reaction rates and equilibria?

    <p>Catalysts lower the activation energy and increase the reaction rate, but do not affect the equilibrium point.</p> Signup and view all the answers

    What is the role of the enzyme-substrate complex in enzyme-catalyzed reactions?

    <p>It is central to the action of enzymes.</p> Signup and view all the answers

    Which mechanism by which the enzyme itself undergoes a conformational change when the substrate binds, induced by multiple weak interactions with the substrate?

    <p>Induced fit</p> Signup and view all the answers

    What is the measure of the affinity an enzyme has for its substrate, as the lower the value of Km, the more efficient the enzyme is at carrying out its function at a lower substrate concentration?

    <p>Km (Michaelis constant)</p> Signup and view all the answers

    What type of catalysis occurs when a transient covalent bond forms between the enzyme and the substrate?

    <p>Covalent catalysis</p> Signup and view all the answers

    What serves to bring specific functional groups on the enzyme into the proper position to catalyze the reaction?

    <p>Induced fit</p> Signup and view all the answers

    What is the discipline focused on determining the rate of a reaction and how it changes in response to changes in experimental parameters?

    <p>Enzyme kinetics</p> Signup and view all the answers

    What is the Michaelis-Menten equation for a one-substrate enzyme-catalyzed reaction?

    <p>$V0 = Vmax\frac{[S]}{Km + [S]}$</p> Signup and view all the answers

    What does a Lineweaver-Burk plot reveal for competitive inhibition?

    <p>Lines intersect at the y-axis</p> Signup and view all the answers

    What happens to the apparent Km in the presence of an uncompetitive inhibitor?

    <p>Increases</p> Signup and view all the answers

    What is the relationship between V0, Vmax, [S], and Km in the Michaelis-Menten equation?

    <p>$V0 = Vmax\frac{[S]}{Km + [S]}$</p> Signup and view all the answers

    What is the equation for the dissociation constant, Kd, for reactions with two steps?

    <p>$k2 + k^{-1}Km = k1$</p> Signup and view all the answers

    What is the rate equation for a second-order reaction involving compounds S and T?

    <p>$V = k[ST]$</p> Signup and view all the answers

    What type of interactions mediate the interactions between enzymes and substrates?

    <p>Ionic interactions and the hydrophobic effect</p> Signup and view all the answers

    What is the range in which enzymes enhance rates of reactions?

    <p>5 to 17 orders of magnitude</p> Signup and view all the answers

    What type of interactions between enzyme and substrate lower the activation energy?

    <p>Covalent interactions</p> Signup and view all the answers

    What overcomes barriers to reaction such as the entropy of molecules in solution and substrate distortion?

    <p>Binding energy</p> Signup and view all the answers

    What serves as transient carriers of specific atoms or functional groups in enzymatic reactions?

    <p>Coenzymes such as biotin, coenzyme A, flavin adenine dinucleotide, lipoate, and others</p> Signup and view all the answers

    What are enzymes classified into based on the type of reaction they catalyze?

    <p>Seven classes with subclasses</p> Signup and view all the answers

    What is the primary factor on which the catalytic activity of enzymes depends?

    <p>The integrity of the native protein conformation</p> Signup and view all the answers

    What was the name given to the molecules detected in cell-free yeast extracts that could ferment sugar to alcohol?

    <p>Enzymes</p> Signup and view all the answers

    What do enzyme active sites use to lower the activation barrier of catalyzed reactions?

    <p>Binding energy</p> Signup and view all the answers

    What is the rate equation for a first-order reaction?

    <p>$V = k[S]$</p> Signup and view all the answers

    What type of interactions between enzyme and substrate lower the activation energy?

    <p>Covalent interactions</p> Signup and view all the answers

    What is the relationship between rate constant k and activation energy ∆G‡?

    <p>Inverse and exponential</p> Signup and view all the answers

    What do enzymes enhance rates in the range of?

    <p>5 to 17 orders of magnitude</p> Signup and view all the answers

    What type of reaction depends on the concentration of two different compounds?

    <p>Second-order reaction</p> Signup and view all the answers

    What is the primary factor on which the catalytic activity of enzymes depends?

    <p>Substrate concentration</p> Signup and view all the answers

    What serves as transient carriers of specific atoms or functional groups in enzymatic reactions?

    <p>Coenzymes</p> Signup and view all the answers

    What are enzymes classified into based on the type of reaction they catalyze?

    <p>Seven classes</p> Signup and view all the answers

    What do enzyme active sites use to lower the activation barrier of catalyzed reactions?

    <p>Binding energy</p> Signup and view all the answers

    What is the measure of the affinity an enzyme has for its substrate, as the lower the value of $K_m$, the more efficient the enzyme is at carrying out its function at a lower substrate concentration?

    <p>$K_m$</p> Signup and view all the answers

    What is the consequence of excessive activity of an enzyme?

    <p>Increased risk of disease</p> Signup and view all the answers

    What serves as practical tools in chemical engineering, food technology, and agriculture?

    <p>Enzymes</p> Signup and view all the answers

    What is the primary factor on which the catalytic activity of enzymes depends?

    <p>Substrate concentration</p> Signup and view all the answers

    What is the role of enzymes in chemical reactions?

    <p>Catalyze reactions</p> Signup and view all the answers

    What are the fundamental conditions for life according to the text?

    <p>Self replication and chemical reactions catalyzed by enzymes</p> Signup and view all the answers

    What is the relationship between the transition state and the ground state in a reaction?

    <p>The transition state is the point at which decay to substrate or product are equally likely, while the ground state is the starting point for the reaction</p> Signup and view all the answers

    What is the activation energy (∆G‡) in a reaction?

    <p>The difference between the ground state energy level and the transition state energy level</p> Signup and view all the answers

    What do catalysts do to affect reaction rates and equilibria?

    <p>Lower the activation energy and increase the reaction rate without affecting the equilibrium point</p> Signup and view all the answers

    What is the relationship between equilibrium constant (K′eq) and standard free-energy change (∆G′°)?

    <p>∆G′° = −RT ln K′eq</p> Signup and view all the answers

    What is the biochemical standard free-energy change, ∆G′°, at pH 7.0?

    <p>∆G′° = the standard free energy change at pH 7.0</p> Signup and view all the answers

    What is the Michaelis constant, Km, a measure of?

    <p>The affinity an enzyme has for its substrate</p> Signup and view all the answers

    What is the primary function of induced fit in enzyme catalysis?

    <p>To bring specific functional groups on the enzyme into the proper position to catalyze the reaction</p> Signup and view all the answers

    What type of catalysis occurs when a transient covalent bond forms between the enzyme and the substrate?

    <p>Covalent catalysis</p> Signup and view all the answers

    What does the maximum rate of the reaction, Vmax, represent?

    <p>The maximum rate of the reaction when all the enzyme’s active sites are saturated with substrate</p> Signup and view all the answers

    What is the role of metal ions in enzyme catalysis?

    <p>To mediate oxidation-reduction reactions by reversible changes in the metal ion’s oxidation state</p> Signup and view all the answers

    What is the relationship between substrate concentration and initial reaction rate, as expressed by the Michaelis-Menten equation?

    <p>$V_0 = \frac{V_{max}[S]}{K_m + [S]}$</p> Signup and view all the answers

    What type of plot yields a straight line for enzymes obeying the Michaelis-Menten relationship?

    <p>Lineweaver-Burk plot of 1/V0 versus 1/[S]</p> Signup and view all the answers

    What happens to the apparent $K_m$ in the presence of an uncompetitive inhibitor?

    <p>Increases by the factor α</p> Signup and view all the answers

    What is the equation for the Lineweaver-Burk plot?

    <p>$\frac{1}{V_0} = \frac{1}{V_{max}} + \frac{1}{K_m[S]}$</p> Signup and view all the answers

    What does a Lineweaver-Burk plot reveal for competitive inhibition?

    <p>Lines intersect at the y axis</p> Signup and view all the answers

    Study Notes

    Enzymes: Key Principles and Characteristics

    • Enzymatic reactions occur in specialized pockets called active sites where the conversion of a substrate to a product takes place.
    • Enzymes bind most tightly to the transition state of the catalyzed reaction, using binding energy to lower the activation barrier.
    • Enzyme active sites are organized by evolution to facilitate multiple mechanisms of chemical catalysis simultaneously.
    • Many enzymes are regulated through reversible covalent modification, binding of allosteric modulators, proteolytic activation, noncovalent binding to regulatory proteins, and elaborate regulatory cascades.
    • Biological catalysis was first recognized in the late 1700s, and the name "enzymes" was given to the molecules detected in cell-free yeast extracts that could ferment sugar to alcohol.
    • Most enzymes are proteins, and their catalytic activity depends on the integrity of the native protein conformation.
    • Enzymes have a wide range of molecular weights, from 12,000 to over 1 million, and may require additional chemical components such as cofactors and coenzymes.
    • Inorganic ions such as Cu2+, Fe2+/Fe3+, K+, Mg2+, Mn2+, Mo, Ni2+, and Zn2+ serve as cofactors for various enzymes.
    • Coenzymes such as biotin, coenzyme A, flavin adenine dinucleotide, lipoate, and others serve as transient carriers of specific atoms or functional groups.
    • Enzymes may contain prosthetic groups, and the complete catalytically active enzyme together with its bound coenzyme and/or metal ions is known as a holoenzyme.
    • Enzymes are classified into seven classes based on the type of reaction catalyzed, each with subclasses, and most enzymes have trivial names in addition to their systematic and enzyme commission numbers.
    • Each enzyme has a four-part enzyme commission number (E.C. Number) and a systematic name that classifies them based on the type of reaction they catalyze.

    Enzymes: Key Principles and Characteristics

    • Enzymatic reactions occur in specialized pockets called active sites where the conversion of a substrate to a product takes place.
    • Enzymes bind most tightly to the transition state of the catalyzed reaction, using binding energy to lower the activation barrier.
    • Enzyme active sites are organized by evolution to facilitate multiple mechanisms of chemical catalysis simultaneously.
    • Many enzymes are regulated through reversible covalent modification, binding of allosteric modulators, proteolytic activation, noncovalent binding to regulatory proteins, and elaborate regulatory cascades.
    • Biological catalysis was first recognized in the late 1700s, and the name "enzymes" was given to the molecules detected in cell-free yeast extracts that could ferment sugar to alcohol.
    • Most enzymes are proteins, and their catalytic activity depends on the integrity of the native protein conformation.
    • Enzymes have a wide range of molecular weights, from 12,000 to over 1 million, and may require additional chemical components such as cofactors and coenzymes.
    • Inorganic ions such as Cu2+, Fe2+/Fe3+, K+, Mg2+, Mn2+, Mo, Ni2+, and Zn2+ serve as cofactors for various enzymes.
    • Coenzymes such as biotin, coenzyme A, flavin adenine dinucleotide, lipoate, and others serve as transient carriers of specific atoms or functional groups.
    • Enzymes may contain prosthetic groups, and the complete catalytically active enzyme together with its bound coenzyme and/or metal ions is known as a holoenzyme.
    • Enzymes are classified into seven classes based on the type of reaction catalyzed, each with subclasses, and most enzymes have trivial names in addition to their systematic and enzyme commission numbers.
    • Each enzyme has a four-part enzyme commission number (E.C. Number) and a systematic name that classifies them based on the type of reaction they catalyze.

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