AP BIOLOGY

Detailed explanation-1: -A ligand can bind either reversibly or irreversibly to a receptor. The action is produced by interacting the drug binding to the receptor to either activate or antagonise the receptor. A drug-receptor interaction can open or close an ion channel across the cell membrane.

Detailed explanation-2: -Because the binding interaction is non-covalent, it’s reversible; avidin and biotin can associate to form the avidin-biotin complex (the forward reaction), and at the same time the complex can dissociate to release the two individual molecules again (the reverse reaction).

Detailed explanation-3: -Ligand release is reversible: removal of the input signal allows the binding site to reassemble and the ligand to return to its bound state.

Detailed explanation-4: -The protein-ligand complex is a reversible non-covalent interaction between two biological (macro)molecules.

Detailed explanation-5: -Reversible means that the radiotracer will dissociate from the receptor-ligand complex with some regularity during the course of the imaging experiment, that is, that the ratio of the “on” rate of binding to the “off” rate of dissociation is not exceedingly large.