The term saturation refers to the fraction of total binding sites that are occupied at any given time.
When more than one type of ligand can bind to a binding site, competition ensues.
An equilibrium exists between unbound ligands and bound ligands.
Binding sites also exhibit chemical specificity, a measure of the types of ligands that will bond, and affinity, which is a measure of the strength of the chemical bond.
A more specific type of binding site is the transcription factor binding site, present on DNA.
Drawing the active site of an enzyme