Keywords: GPCRs; G protein-coupled receptors; KNF; Koshland, Nemethy and Filmer; Hb; hemoglobin; IHP; inositol haxaphosphate; Mb; myoglobin; MWC; Monod, Wyman and Changeux; Ngb; neuroglobin; TTS; tertiary two-state allosteric model; Cooperative oxygen binding; Allo