Factors Affecting Enzyme Activity
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Questions and Answers

What is the effect of temperature on enzyme action up to the optimum temperature?

  • Rate of reaction increases gradually. (correct)
  • Rate of reaction decreases significantly.
  • Rate of reaction is independent of temperature.
  • Rate of reaction remains constant.

    • At what temperature range do most human enzymes optimally function?

  • 20-30 °C
  • 37-40 °C (correct)
  • 0-10 °C
  • 50-60 °C

    • What happens to the enzyme reaction rate after surpassing the optimum temperature?

  • The rate of reaction decreases due to enzyme denaturation. (correct)
  • The rate of reaction remains stable.
  • The rate of reaction reverses direction.
  • The rate of reaction increases even more.

    • Which of the following factors affects enzyme activity by altering the ion concentration in the environment?

    <p>Concentration of ion activators (C)</p> Signup and view all the answers

    What is the optimal pH range for most enzymes functioning in the human body?

    <p>7.35 - 7.45 (D)</p> Signup and view all the answers

    What is the effect of pH on enzyme activity?

    <p>Each enzyme has a specific optimum pH for maximal activity. (A)</p> Signup and view all the answers

    Which enzyme has an optimum pH below neutral?

    <p>Pepsin (A)</p> Signup and view all the answers

    What role does activation energy play in enzyme activity?

    <p>Lowering activation energy enhances reaction rates. (B)</p> Signup and view all the answers

    What is the pH optimum for pepsin to maintain maximum enzymatic activity?

    <p>1.6 (B)</p> Signup and view all the answers

    What happens to the reaction rate when substrate concentration increases, according to enzyme kinetics?

    <p>It remains unaffected after a certain point. (A)</p> Signup and view all the answers

    Which ion is known to activate salivary amylase?

    <p>Chloride ion (B)</p> Signup and view all the answers

    In the Michaelis-Menten equation, what does Km represent?

    <p>The substrate concentration that produces half maximal velocity. (B)</p> Signup and view all the answers

    What occurs when the pH of an enzyme-catalyzed reaction moves away from its optimum pH?

    <p>Decreased enzyme activity (D)</p> Signup and view all the answers

    Which enzyme is characterized by low Km and acts effectively at low substrate concentrations?

    <p>Hexokinase (A)</p> Signup and view all the answers

    Why is the Lineweaver-Burk plot useful in enzyme kinetics?

    <p>It simplifies the determination of Vmax and Km. (B)</p> Signup and view all the answers

    How does the concentration of coenzymes influence enzymatic reactions?

    <p>Increases rate with higher concentration (D)</p> Signup and view all the answers

    What is the effect of substrate concentration on the rate of an enzyme-catalyzed reaction?

    <p>It increases to a point then levels off (D)</p> Signup and view all the answers

    What effect do competitive inhibitors have on enzyme activity?

    <p>They decrease or stop the enzyme activity by competing with the substrate. (B)</p> Signup and view all the answers

    In enzyme kinetics, what characterizes enzymes with a high Km?

    <p>They have a low affinity for substrates and act at high substrate concentrations. (C)</p> Signup and view all the answers

    What can contribute to the decrease in enzyme reaction rate over time?

    <p>Exhaustion of substrates (A)</p> Signup and view all the answers

    Which enzyme's activity is influenced by pH in a way that the enzyme denatures outside its optimal environment?

    <p>Pepsin (D)</p> Signup and view all the answers

    What is typically plotted on the Y-axis of a Michaelis-Menten plot?

    <p>Reaction velocity (B)</p> Signup and view all the answers

    What is the effect of metal ion activators on enzymatic reactions?

    <p>They have varying effects based on the enzyme (A)</p> Signup and view all the answers

    What is the primary challenge when directly plotting Vi versus [S] in enzyme kinetics?

    <p>Underestimating the value of Vmax. (A)</p> Signup and view all the answers

    Flashcards

    Enzyme Optimum Temperature

    The temperature at which an enzyme's activity is highest, converting the maximum amount of substrate to products.

    Enzyme denaturation

    The loss of an enzyme's 3D shape and function due to high temperatures.

    Enzyme Optimum pH

    The pH level where an enzyme functions most effectively.

    Enzyme Activity

    The rate at which an enzyme catalyzes a reaction.

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    Temperature Effect on Enzymes

    Enzyme activity increases with temperature until an optimum point is reached, then it decreases due to enzyme denaturation.

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    pH Effect on Enzymes

    Enzymes have an optimal pH range. Moving outside that range reduces or stops enzyme activity.

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    Substrate Concentration

    The amount of the substance an enzyme works on.

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    Enzyme Concentration

    The amount of enzyme present in a reaction.

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    Enzyme Activity & pH

    Enzyme activity is highly dependent on pH. Optimal pH ranges exist for each enzyme, with activity decreasing significantly outside this range due to changes in enzyme and substrate ionization states and potential denaturation.

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    Enzyme Reaction Rate & Time

    Enzyme reaction rates decrease over time due to substrate depletion, product buildup, and pH drift away from optimum conditions.

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    Enzyme Concentration Effect

    Enzyme reaction rates scale directly with enzyme concentration, as long as substrate is readily available and conditions remain consistent.

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    Substrate Concentration & Vmax

    Increasing substrate concentration usually increases reaction rate until a maximum speed (Vmax) is achieved, where enzymes are working at full capacity.

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    Optimal pH

    The pH at which an enzyme functions most efficiently.

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    Ionic Activators

    Some enzymes require metal ions (or other ions) for activity. Increased ion concentration increases reaction rate.

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    Enzyme Kinetics

    The study of how quickly an enzyme works

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    Michaelis-Menten Equation

    An equation that describes how enzyme activity depends on substrate concentration

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    Michaelis Constant (Km)

    The substrate concentration needed to reach half the maximum reaction rate (Vmax)

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    Vmax

    The maximum rate of an enzyme-catalyzed reaction

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    Low Km Enzyme

    Enzyme with high affinity for substrate, works fast at low substrate concentrations

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    High Km Enzyme

    Enzyme with low affinity for substrate, needs high substrate concentrations to work fast

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    Lineweaver-Burk Plot

    A plot of 1/V vs. 1/[S] used to determine Vmax and Km more precisely

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    Enzyme Inhibitor

    A substance that reduces or stops enzyme activity

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    Study Notes

    Factors Affecting Enzyme Activity

    • Enzyme activity is influenced by various factors, impacting the rate of reactions they catalyze.
    • Key factors affecting enzyme activity are: temperature, pH, concentration of coenzymes, concentration of ion activators (metals), enzyme concentration, substrate concentration, and inhibitors.
    • Time also impacts enzyme activity, as substrate concentration diminishes over time and end products may accumulate, leading to negative feedback inhibition on enzyme activity. Changes in pH, away from the optimum, also affect reaction rate.

    Temperature

    • Increasing temperature generally accelerates enzyme activity up to an optimum temperature.
    • Optimum temperature: The temperature where enzyme activity is highest, maximizing the conversion of substrate to products.
    • The optimum temperature for human enzymes typically lies between 37-40°C.
    • Above the optimum temperature, enzyme activity decreases due to denaturation (60-65°C).
    • Increased temperature initially increases kinetic energy of substrates, reducing activation energy, and accelerating collisions between molecules.

    pH

    • Each enzyme exhibits optimal activity at a specific pH range.
    • Pepsin's optimal pH is 1.5-2.0.
    • Pancreatic enzymes operate optimally at 7.5-8.0.
    • Salivary amylase functions best around pH 6.8.
    • The optimal pH range for most enzymes is 7.35-7.45.
    • Significant deviations from the optimal pH cause enzyme denaturation, impacting function.
    • pH changes affect ionization of enzyme and substrate amino acid side chains in the active site; this alters the enzyme's structure and can disable catalysis.

    Time

    • Enzyme-catalyzed reactions slow down over time.
    • This is due to: the depletion of substrate, buildup of product which can cause feedback inhibition (some products can inhibit the initial reaction), and changes in pH moving away from the optimum.

    Enzyme and Coenzymes/ Co-factors

    • Increased coenzyme concentration leads to a corresponding increase in reaction rate for those enzymes requiring coenzymes.
    • Increased activator metal ion concentration leads to increased reaction rate of enzymes requiring those ions.

    Enzyme Concentration

    • The rate of enzyme-catalyzed reactions is directly proportional to the enzyme concentration. This relationship holds true when substrate is abundant and other conditions remain constant.

    Substrate Concentration

    • Increasing substrate concentration initially increases the reaction rate, reaching a maximum rate known as Vmax.
    • At Vmax, all enzyme active sites are saturated with substrate, and further increases in substrate concentration will not affect reaction rate.

    Inhibitors

    • Inhibitors reduce or stop enzyme activity.
    • Competitive inhibitors compete with substrates, binding to the active site.
    • Non-competitive inhibitors bind to sites other than the active site, affecting enzyme functionality.

    Enzyme Kinetics

    • Enzyme kinetics deals with the rates of enzymatic reactions.
    • The Michaelis-Menten equation describes the relationship between initial reaction rate (Vi) and substrate concentration ([S]) featuring a constant called the Michaelis constant (Km):
    • Vi = (Vmax [S]) / ([S] + Km)

    Michaelis-Menten Plot

    • This plot depicts the relationship between reaction velocity and substrate concentration.
    • It is difficult to measure Vmax and Km precisely from this plot.

    Michaelis Constant (Km)

    • Km represents the substrate concentration where the reaction rate is half of the maximal velocity (Vmax).
    • Higher Km values mean the enzyme has a lower affinity for its substrate, requiring a higher substrate concentration for half-maximal activity.
    • Lower Km values indicate higher affinity of the enzyme for its substrate.

    Enzymes with Low/High Km

    • Enzymes with low Km have a high affinity for their specific substrates, showing maximal activity at relatively low substrate concentrations.
    • Conversely, enzymes with high Km show low affinity for their substrates, exhibiting high activity only at high substrate concentrations.

    Lineweaver-Burk Plot

    • Linear plot representing the reciprocal of the Michaelis-Menten equation.
    • Vmax and Km calculation from the plot is more precise compared to the original Michaelis-Menten plot.

    Enzyme Inhibitors

    • Inhibitors are substances that reduce or stop enzyme activity.
    • Competitive inhibitors bind to the active site.
    • Non-competitive inhibitors bind to a site other than the active site, altering enzyme shape.

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    Related Documents

    Factors Affecting Enzyme Activity PDF

    Description

    Explore the key factors influencing enzyme activity in this quiz. You'll learn about temperature, pH, concentration levels, and how these elements affect enzymatic reactions. Dive into the science of enzymes and test your knowledge on their operational dynamics.

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