Enzyme

    Cards (28)

    • Enzymes are biological catalysts that speed up chemical reactions without being used up or changed.
    • A substrate is a molecule that which an enzyme acts on
    • The functional part of an enzyme is called the active site
    • Describe the lock and key model of enzyme action: Enzymes have an active site of specific shape; the substrate that is a complemenatry shape binds to active site
    • The specific 3D shaped active site of an enzyme is determined by its sequence of amino acids (primary structure)
    • When a substrate binds to the active site we call the resulting structure an enzyme-substrate complex
    • A substrate does not have the same shape as the active site it has a complementary shape.
    • Enzymes are a type of biological molecule called proteins
    • Explain induced fit model in enzymes:
      upon binding the active site of the enzyme molds around the substrate; active site becomes complementary
    • Increasing the temperature affects the rate of enzyme controlled reactions by:
      • increase in kinetic energy between molecules
      • molecule have more succesful collisions so more enzyme substrate complexes formed
      • rate of reaction increases
      • after optimum reached denaturation; loss of tertiary structure as break of bonds
      • active site altered so substrate can fit
    • decreasing temperature affects the rate of enzyme controlled reactions by:
      • decrease in kinetic energy between molecules
      • molecule have less succesful collisions so less enzyme substrate complexes formed
      • rate of reaction decreases
    • enzymes increase rate of reaction by lowering the activation energy of the reaction
    • Competitive inhibitors have similar shapes to the substrate, hence competing with the substrate for the available active site. Competitive inhibitors are not permanently bound to the enzyme active site
    • Non-competitive inhibitors are chemicals that bind to the enzyme and change its shape; eventually all enzymes will bind to non-competitive inhibitors.
    • How does the structure of enzymes relate to its function:
      • specific 3D tertiary structure
      • substrate complementary shape
      • substrate can bind to active site
    • How does competitve inhibitors affect the activity of enzymes?
      • Inhibitor has similar shape to subtrate
      • competes for active site
      • fewer enzyme substrate complexes formed but cannot react with the enzyme
    • How does incompetitve inhibitors affect the activity of enzymes:
      • Inhibitor differs to shape of substate
      • Bind to allosteric site
      • Alters active site so substrate can not bind and no substrate enzyme complexes formed
    • How does substrate concentration affect the activity of enzymes?
      Substrate limiting factor
      Enzyme active sites fully occupied
    • How does pH affect the activity of enzymes:
      Ionic bonds holding tertiary structure break, active site denatures and substrate no longer binds to it charges of amino acid in active site affected: so fewer E-S complexes formed
    • Activation energy: minimum amount of energy required to bring particles into close contact; so that they will collide and react
    • Heterotrophs are organisms that obtain their nutrients by consuming other organisms
    • extracellular enzymes are enzymes that are released from the cells that make them
    • Intracellular enzymes are found in the cytoplasm or attached to cell membranes, their action takes place inside the cells
    • the enzyme lock and key hypothesis explains:
      • Enzyme specificity
      • The loss of activity when enzymes denature
    • Co factors are an additional non-protein molecule that is needed by some enzymes to help the reaction
    • Prosthetic groups are tightly bound cofactors
    • Coenzymes are cofactors that are bound and released easily
    • How does concentration affects to enzyme controlled reactions:
      Proportional to rate of reaction until there are more substrates than enzymes present
      Rate of reaction increases
      • Substrate binds to active site, but more enzymes are available
      • Rate increases if more substrate is added
      • Eventually, curve becomes constant (no increased rate)
      • Substrates occupy all active sites (all enzymes)
      • Adding more substrate won't yield more product, as no more active sites are available