Do Now Take out your: Vocabulary notes + Toothpickase lab Answer the following questions: What are the three factors that affect the rate at which an enzyme operates? On the graph, which pathway is NOT catalyzed? What letter corresponds to activation energy? Write 2-3 sentences describing an analogy for an enzyme.

ENZYME INHIBITION

Inhibitors Inhibitors are chemicals that reduce the rate of enzymic reactions The are usually specific and they work at low concentrations They block the enzyme but they do not usually destroy it Many drugs and poisons are inhibitors of enzymes in the nervous system

The effect of enzyme inhibition Irreversible inhibitors: Combine with the functional groups of the amino acids in the active site, irreversibly Examples: nerve gases and certain pesticides

The effect of enzyme inhibition Reversible inhibitors: Binds to the active site, but can be removed

The effect of enzyme inhibition Competitive: These compete with the substrate molecules for the active site The inhibitor’s action is proportional to its concentration Resembles the substrate’s structure closely Enzyme inhibitor complex Reversible reaction E + I EI

The effect of enzyme inhibition Non-competitive: These are not influenced by the concentration of the substrate. It inhibits by binding irreversibly to the enzyme but not at the active site Examples

Applications of inhibitors Poisons snake bite, plant alkaloids and nerve gases Medicine antibiotics, sulphonamides, sedatives and stimulants