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Vincenzo Fogliano » 6.Myoglobin and hemoglobin


Preliminary worning!

These lesson slides only provide an outline.

You must study miyglobin and hemoglobin using a Biochemistry textbook.

Myoglobin (Mb)


Hemoglobin (Hb)

Protein formed by
4 subunits
each of them is 
similar to myoglobin.

Protein formed by 4 subunits each of them is similar to myoglobin.


EME and oxygen

Proxymal Histidine.

Proxymal Histidine.


Myoglobin and Hemoglobin structure

  • Differences in iron oxydation.
  • Effect of amino acid moiety on Fe-CO affinity.
  • Switch between taut “T” and relaxed “R” state.

Myoglobin saturation curve


Hemoglobin saturation curve

Hb affinity curve for  different human populations.
Fetal Hb affinity .

Hb affinity curve for different human populations. Fetal Hb affinity .


Modulators of Hb-O2 affinity

Stabilizers of T form favour the release of oxygen so the deoxy-Hb:

  • 2,3 BPG;
  • Low pH;
  • Increase in CO2 (Bohr effect).

Physiological relevance of Bohr effect

In the tissue the increase in [CO2] leads to a pH decrease

CO2 +H2O → HCO3- + H+

At low pH ionic interaction between some amino acids is favoured (Es His 146 Asp 94) and the T form is stabilised.
CO2 directly binds the free amino group forming carbamate adducts stabilizing T form and contributing about 25% of CO2 overall transportation.

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