Cooperativity
Cooperativity is a phenomenon displayed by systems involving identical or near-identical elements, which act dependently of each other, relative to a hypothetical standard non-interacting system in which the individual elements are acting independently. One manifestation of this is enzymes or receptors that have multiple binding sites where the affinity of one binding site for a ligand is apparently increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to another binding site.