B4: Enzymes

  1. Biological catalysts

  • enzymes are:

    • Catalysts: speed up the rate of a chemical reaction without it being changed/used up

    • proteins

    • biological catalysts

    • maintain reaction speeds of all metabolic reactions to sustain life

  • enzymes are specific to one particular substrate → complementary shape to the active site of the substrate

    • product made from the substrate and released

  • Enzyme action:

    • when the substrate moves into the enzyme’s active site → enzyme-substrate complex

      • after reaction: products leave the enzyme’s active site (no longer fit) → free to take up another substrate

    • enzymes and substrates randomly move about in solution

  1. Factors that affect enzymes

  • Temperature

    • work fastest at their optimum temperature

      • more energy → faster they move and number of collisions with substrates increases

      • low temperatures do not denature enzymes (work slower)

    • temperature too high → denature

      • substrates cannot fit into denatured enzymes (active site has been lost)

    • denaturation is irreversible

  • pH

    • Optimum pH of most enzymes: 7

      • acidic enzymes: pH 2

      • alkaline enzymes (like duodendum): pH 8/9

    • pH too high/low: bonds holding chains together that make up a nutrient can be destroyed → changes shape of active site (substrate can no longer fit)

    • Too far from pH → enzyme denatures