Enzymes and Cofactors
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Questions and Answers

What is the primary function of oxidoreductase enzymes?

  • To cleave molecules by help of water
  • To catalyze oxidation and reduction reactions (correct)
  • To facilitate the removal of groups from substrates by hydrolysis
  • To catalyze the formation of covalent bonds between molecules
  • Which vitamin is required for the synthesis of FAD and FMN?

  • Vitamin C
  • Vitamin Riboflavin (correct)
  • Vitamin B12
  • Vitamin Thiamine
  • What is the primary role of cofactors in enzyme activity?

  • To serve as a metal ion required for enzyme activity (correct)
  • To serve as a bridge between the enzyme and substrate
  • To facilitate the binding of substrate to the enzyme
  • To provide energy for the enzyme-catalyzed reaction
  • What is the consequence of mutations in the SOD enzyme?

    <p>Development of amyotrophic lateral sclerosis (D)</p> Signup and view all the answers

    What is the primary mechanism of the induced fit model of enzyme activity?

    <p>Binding of the substrate to the enzyme causes a conformational change in the enzyme (B)</p> Signup and view all the answers

    At what pH does salivary amylase catalyze best?

    <p>pH 7 (B)</p> Signup and view all the answers

    What happens to the activity of an enzyme if the temperature is very high?

    <p>The activity of the enzyme decreases due to denaturation (B)</p> Signup and view all the answers

    What is the significance of a low Km value for an enzyme?

    <p>It indicates a strong affinity of the enzyme towards the substrate (D)</p> Signup and view all the answers

    What is the effect of a competitive inhibitor on the Km and Vmax of an enzyme?

    <p>Km increases, Vmax remains the same (D)</p> Signup and view all the answers

    What is the purpose of acetaldehyde dehydrogenase enzyme?

    <p>To detoxify acetaldehyde produced from breakdown of alcohol (A)</p> Signup and view all the answers

    Study Notes

    Cofactors and Coenzymes

    • TPP (Thiamine Pyrophosphate) is synthesized from Vitamin Thiamine
    • FAD (Flavin Adenine Dinucleotide) and FMN (Flavin Mononucleotide) are synthesized from Vitamin Riboflavin
    • Examples of coenzymes include FAD, FMN, TPP, and others

    Types of Enzymes

    Oxidoreductases

    • Enzymes involved in oxidation-reduction reactions
    • Example: Superoxide Dismutase (SOD), mutations of which lead to Amyotrophic Lateral Sclerosis

    Hydrolases

    • Enzymes that cleave molecules using water
    • Example: Tissue Plasminogen Activator, which cleaves Plasminogen to Plasmin to dissolve clots

    Ligases

    • Enzymes that catalyze synthetic reactions, forming covalent bonds at the expense of high-energy phosphate bonds (usually ATP)
    • Example: Pyruvate Carboxylase

    Enzyme Activity

    • The Induced Fit model is the most accepted model, stating that binding of substrate to enzyme induces a conformational change in the enzyme, directing appropriate amino acids to the active site
    • Factors affecting enzyme activity: availability of enzyme, optimum pH, optimum temperature, coenzymes, and cofactors

    Optimum pH and Temperature

    • Enzymes work best at optimum pH and temperature
    • Examples: Salivary Amylase catalyzes best at pH 7, Pepsin catalyzes best at pH 2, and high temperatures can cause denaturation of enzymes

    Km and Vmax

    • Km is the substrate concentration at which ½ Vmax is reached
    • Low Km value indicates strong affinity of enzyme towards substrate, while high Km reflects weak affinity
    • Vmax is the maximum rate of enzyme activity, where all enzymes are saturated with substrate and are in the ES (Enzyme-Substrate) complex

    Hexokinase and Glucokinase

    • Both catalyze phosphorylation of glucose
    • Hexokinase: present in all cells except hepatocytes and β-cells of pancreas, has low Km (high affinity) for glucose, and works even at low glucose concentrations
    • Glucokinase: present in hepatocytes and β-cells of pancreas, has high Km (low affinity) for glucose, and removes glucose from circulation only after a meal

    Acetaldehyde Dehydrogenase

    • Required to detoxify acetaldehyde from breakdown of alcohol
    • Two types: low Km form and high Km form, with the low Km form breaking down acetaldehyde more efficiently

    Competitive Inhibition

    • A type of reversible inhibition where the inhibitor is a structural analog of the substrate and binds to the active site of the enzyme
    • Examples: Sulfonamides, Trimethoprim, Dicoumarol, Captopril, and Allopurinol

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    Description

    Test your knowledge of enzymes, cofactors, and coenzymes, including their functions, synthesis, and examples. Learn about oxidoreductases, hydrolases, lyases, and ligases, and how they relate to various biological processes.

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