Bke2 Biochemistry Lectures

Lecture 6: Protein chemistry, structure & function II
Reading material: Horton, Chapter 4.

Abstract: Oxygen is transported in mammals by hemoglobin and stored in muscles by myoglobin. Hemoglobin has allosteric properties which makes it suitable for picking up oxygen when the oxygen pressure is high (in the lungs) and release it when the oxygen pressure is low (in the muscles).

Key concepts:
Proteins modify the properties of bound chemical groups (cmp heme in solution and bound to Mb or Hb)
Mb has a hyperbolic oxygen-binding curve
Hb has an S-shaped oxygen-binding curve and binds oxygen tightly at high oxygen pressures, and weakly at low oxygen pressures
Allosteric proteins can exist in two (or more) forms with distinct conformations and properties
Homotropic allosteric effect (co-operative binding)
Heterotropic allosteric effect
Allosteric effects depend on conformational changes induced by binding of various compounds
The Bohr effect: protons promote oxygen release in tissues by stabilising the deoxy form of Hb
2,3-bisphosphoglycerate shifts Mb towards the deoxy form to promote effecient unloading of oxygen.

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