The binding of oxygen (O2) to hemoglobin (HbA) decreases the affinity of HbA for protons (H+) bound at histidine residues and carbon dioxide (CO2) bound chemically as a carbamate at the N-terminus of the HbA (Ferguson and Roughton 1934, Kernohan & Roughton 1968, Klocke 1973, Morrow et al. 1973, Morrow et al. 1976, Tazawa et al. 1983, Kraan & Rispens 1985, Doyle et al. 1987, Mertzlufft & Brandt 1989, Kalhoff et al.1994, Dash & Bassingthwaighte 2010, reviewed in Jensen 2004). This property of HbA is known as the Haldane Effect and facilitates the exchange of CO2 for O2 in the lungs.