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An introduction to Metabolism(Lecture5,chapter8,page 51-75)(exam 2)

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  • What happens when all enzyme molecules have their active sites engaged?
    The enzyme is saturated, and the reaction rate can only be increased by adding more enzyme.
  • How does substrate concentration affect enzyme-catalyzed reaction rates?
    Increasing substrate concentration speeds up the reaction rate until the enzyme becomes saturated.
  • What environmental factors affect enzyme activity?
    Temperature, pH, and specific chemicals can influence enzyme activity.
  • What is the optimal temperature for enzyme activity?
    Each enzyme has an optimal temperature where it catalyzes reactions at the maximum rate before denaturing at higher temperatures.
  • How does the optimal temperature vary between human enzymes and thermophilic bacteria enzymes?
    Human enzymes have an optimal temperature around 30–40°C, while thermophilic bacteria enzymes have an optimal temperature near 75°C.
  • What is the optimal pH for pepsin and trypsin enzymes?
    Pepsin has an optimal pH of 2 (stomach enzyme), and trypsin has an optimal pH of 8 (intestinal enzyme).
  • What are cofactors in enzyme activity?
    Cofactors are nonprotein helpers that bind permanently or reversibly to enzymes; they include inorganic metal ions and organic coenzymes.
  • What is the difference between competitive and noncompetitive enzyme inhibitors?
    Competitive inhibitors bind to the active site blocking substrate binding; noncompetitive inhibitors bind elsewhere causing shape change and reduced activity.
  • How can competitive inhibition be overcome?
    By increasing substrate concentration, which outcompetes the inhibitor for the active site.
  • What characterizes irreversible enzyme inhibitors?
    They form covalent bonds with enzymes, permanently inactivating them, often seen in toxins and poisons.
  • How do mutations affect enzyme evolution?
    Mutations alter amino acid sequences, potentially changing enzyme activity or substrate specificity, which natural selection can favor if beneficial.
  • What is allosteric regulation of enzymes?
    Regulatory molecules bind at one site on a protein and affect enzyme function at a different site, either inhibiting or stimulating activity.
  • How do allosteric activators and inhibitors affect enzyme shape?
    Activators stabilize the active form with functional active sites; inhibitors stabilize the inactive form.
  • What is cooperativity in enzyme activity?
    Substrate binding to one active site triggers shape changes that stabilize the active form of other sites, amplifying enzyme response.
  • What is feedback inhibition in metabolic pathways?
    The end product of a pathway binds to an enzyme early in the pathway to shut down further production, conserving resources.
  • How does compartmentalization affect enzyme function in cells?
    It organizes metabolic pathways by localizing enzymes in specific organelles or complexes, enhancing efficiency.
  • Where are enzymes for the second and third stages of cellular respiration located in eukaryotic cells?
    They are located within mitochondria.