Enzyme action
Enzymes are proteins that act as biological catalysts: they speed up reactions without being used up. Each enzyme has an active site with a shape complementary to its substrate (lock and key), forming an enzyme–substrate complex. Activity rises with temperature up to an optimum (about 37 °C for human enzymes) as molecules collide more often; above it the enzyme denatures: the active site changes shape and the substrate no longer fits. Each enzyme also has an optimum pH.
≈ 40 min