Enzyme Substrate Interaction and Michaelis-Menten Equation
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Questions and Answers

What happens to the rate of an enzyme-catalyzed reaction when the substrate concentration becomes the limiting factor?

  • It remains constant with any further increase in enzyme concentration
  • It becomes independent of the enzyme concentration (correct)
  • It decreases with any further increase in enzyme concentration
  • It continues to increase with any further increase in enzyme concentration

    • What is the relationship between enzyme concentration and reaction rate when substrate concentration is not limiting?

  • Directly proportional (correct)
  • Exponential
  • Inverse
  • Independent

    • What is the significance of the Q10 value in enzyme-controlled reactions?

  • Predicts the enzyme's pH optimum
  • Determines the enzyme specificity
  • Quantifies the rate increase with temperature rise (correct)
  • Indicates the enzyme's optimal temperature

    • Why do cold-water fish die at 30°C?

    <p>Their enzymes denature at this temperature</p> Signup and view all the answers

    What happens to most enzymes at 70°C?

    <p>They denature completely</p> Signup and view all the answers

    What is the pH range preferred by most enzymes for optimal activity?

    <p>Neutral (pH 6-8)</p> Signup and view all the answers

    What induces a change in the enzyme's conformation when it combines with a substrate?

    <p>Stretching of substrate bonds</p> Signup and view all the answers

    What is the primary function of the active site of an enzyme?

    <p>To make the chemical environment suitable for the reaction</p> Signup and view all the answers

    In the Michaelis-Menten equation, what does the KS constant stand for?

    <p>Enzyme-substrate complex concentration</p> Signup and view all the answers

    According to Michaelis and Menten's assumptions, what is a key aspect of the enzymatic reaction?

    <p>Low substrate concentration compared to enzymes</p> Signup and view all the answers

    What is the primary focus of the Michaelis-Menten equation?

    <p>Velocity of enzymatic reactions with a single substrate</p> Signup and view all the answers

    What is one assumption made by Michaelis and Menten about enzyme reactions?

    <p>The process continues essentially to its completion</p> Signup and view all the answers

    What is the Michaelis-Menten constant denoted by in the given equation?

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

    How is enzyme activity commonly expressed?

    <p>Moles of substrate converted to product per unit time</p> Signup and view all the answers

    Why does the rate of an enzyme-catalyzed reaction increase with an increase in substrate concentration?

    <p>More substrate molecules collide with enzyme molecules</p> Signup and view all the answers

    In what scenario would the initial rate of an enzyme-catalyzed reaction be proportional to the concentration of enzyme ([E])?

    <p>[S] &gt; [E]</p> Signup and view all the answers

    How does an increase in enzyme concentration affect the reaction rate?

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

    At what point does an enzyme become saturated in terms of substrate concentration?

    <p>When further increase in substrate has no effect on reaction rate</p> Signup and view all the answers

    What is the primary role of inorganic metal ions in enzyme catalysis?

    <p>Forming coordination bonds with side chains at the active site</p> Signup and view all the answers

    Which coenzyme is responsible for transferring acyl groups during metabolic reactions?

    <p>Coenzyme A</p> Signup and view all the answers

    What is the function of a transient carrier coenzyme in biochemical reactions?

    <p>Transferring specific atoms or functional groups</p> Signup and view all the answers

    Which vitamin serves as a dietary precursor for mammals and is essential for various carboxylation reactions?

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

    What is the main function of inhibitors on enzyme activities?

    <p>To lower the enzyme's catalytic rate</p> Signup and view all the answers

    Which inorganic element acts as a cofactor for the enzyme carbonic anhydrase?

    <p>Zn2+</p> Signup and view all the answers

    What is a coenzyme when it comes to enzyme cofactors?

    <p>An organic compound</p> Signup and view all the answers

    Which type of cofactor is referred to as a prosthetic group?

    <p>Organic or inorganic compounds tightly bound to the apoenzyme</p> Signup and view all the answers

    What is the composition of a holoenzyme?

    <p>Apoenzyme + Coenzyme</p> Signup and view all the answers

    In enzyme catalysis, coenzymes often function as what?

    <p>Intermediate carriers of electrons</p> Signup and view all the answers

    What role does NAD play in certain oxidations/reductions?

    <p>Carrier of electrons</p> Signup and view all the answers

    What distinguishes coenzymes from other enzyme cofactors?

    <p>Their association with the enzyme is transient</p> Signup and view all the answers

    Study Notes

    Enzyme Catalysed Reactions

    • The rate of an enzyme-catalysed reaction is directly proportional to the enzyme concentration when the substrate concentration is not limiting.
    • Increasing enzyme concentration will increase the rate of reaction until the substrate concentration becomes the limiting factor.

    Effect of Temperature on Velocity

    • Enzymes have an optimal temperature, with a balance between the Q10 (temperature coefficient) and denaturation.
    • Q10 is the increase in reaction rate with a 10°C rise in temperature, with a typical value of 2-3 for chemical reactions.
    • Most enzymes are fully denatured at 70°C, but some can withstand high temperatures up to 100°C.

    Effect of pH Value on Velocity

    • The pH optimum varies for different enzymes, with most having a neutral pH (6-8).
    • When a substrate combines with an enzyme, it induces a change in the enzyme's conformation, making the chemical environment suitable for the reaction.

    Michaelis-Menten Equation

    • The Michaelis-Menten equation describes the velocity of enzymatic reactions, with the equation: VO = Vmax[S] / Km + [S]
    • VO is the initial velocity of the reaction, Vmax is the maximum velocity, Km is the Michaelis-Menten constant, and [S] is the substrate concentration.

    Enzyme Velocity and Activity

    • Enzyme activity is expressed by the initial rate (V0) of the reaction being catalyzed.
    • Enzyme activity is measured in moles of substrate converted to product per unit time.
    • Velocity decreases as time increases due to factors such as substrate depletion, product inhibition, pH change, and cofactor depletion.

    Effect of Substrate Concentration

    • An increase in substrate concentration increases the rate of enzyme-catalysed reaction, but eventually reaches a point of saturation where further increases have no effect.

    Effect of Enzyme Concentration

    • The initial rate of an enzyme-catalysed reaction is proportionate to the concentration of enzyme.

    Coenzymes and Cofactors

    • Coenzymes are organic molecules that are derivatives of vitamins and act as transient carriers of specific atoms or functional groups.
    • Examples of coenzymes include Coenzyme A, Flavin adenine dinucleotide, and Nicotinamide adenine dinucleotide.
    • Inorganic metal ions such as Cu2+, Fe2+/Fe3+, K+, Mg2+, Mn2+, Mo, Ni2+, Se, and Zn2+ serve as cofactors by forming coordination bonds with side chains at the active site and with the substrate.

    Inhibition of Enzyme Activities

    • Inhibitors are molecules that act directly on an enzyme to lower its catalytic rate, often at low concentrations and with specificity.
    • Cofactors can be organic compounds (coenzymes) or inorganic groups (metal ions).
    • Prosthetic groups are organic or inorganic compounds that are tightly bound to the apoenzyme.

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    Description

    Learn about how substrates combine with enzymes to induce a change in conformation, create a suitable chemical environment for reactions, and lower the activation energy. Explore the Michaelis-Menten equation and different mechanisms of enzyme reactions proposed by biochemists.

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