Page "Hemoglobin" Paragraph 27

Hemoglobin exists in two forms, a taut form ( T ) and a relaxed form ( R ).

Various factors such as low pH, high CO < sub > 2 </ sub > and high 2, 3 BPG at the level of the tissues favor the taut form, which has low oxygen affinity and releases oxygen in the tissues.

Conversely, a high pH, low CO < sub > 2 </ sub >, or low 2, 3 BPG favors the relaxed form which can better bind oxygen.