1. Receptors: Answer -Part of the cell that is exposed to the outside environment -Causes specific action in the cell when activated -Lock and key mechanism May interact with a cell or may not 2. Ligand: Answer molecules that bind to a receptor 3. Agonist: Answer -a molecule that, by binding to a receptor site, stimulates a response -Any chemical that reacts with the extracellular receptor to cause a physiologicchange in the cell 4. Antagonist: Answer -Reacts with the receptor, but does not cause the physiologic changein the cell -Reversal agent for drug overdoses -Used to induce a biological response by blocking one pathway ("beta blockers") 5. Enzymes: Answer -Chemicals that cause degradation of other chemicals, but are notaffected by the reaction -Main ones to know are the cytochrome P450 enzymes 6. Inducers: Answer -rapid drug breakdown with rapid half-life