•Hb can exist in 2 different forms: T-form and R-form.
•T-form (T = „tense“) has a much lower oxygen affinity than the R-form. The subunits of Hb are held together by electrostatic interactions. The binding of the first O2 molecule to subunit of the T-form leads to a local conformational change that weakens the association between the subunits → R-form („relaxed“) of Hb.
•Increasing of oxygen partial pressure causes the conversion of T-form to R-form.
• T R
• Hb + ↑pO2 HbO2