Transport of O2 with haemoglobin

TRANSPORT OF O2WITH HAEMOGLOBIN
  • After entry into the blood plasma, most of the O2 enters across the red cell membrane into the cell. The major portion of O2 is carried by blood is not in physical solution but is associated with haemoglobin molecule inside the red cells.

  • If plasma is exposed to an atmosphere of 100mm.Hg partial pressure of O2 only 0.3ml of O2 is taken up, But when blood is similarly allowed to equilibrate at an O2 tension of 100mmHg, it can carry 19 – 20 ml of O2/ 100ml of blood.
  • Hb present within erythocytes does the extra uptake.
  • Each Hb molecule contains 4 heme groups. Each heme molecule contains one Fe++ atom in a reduced state.
  • Each molecule of Hb can combine with 4 molecules of O2 depending on the relative concentration of Hb and O2 in blood. When reduced Hb combines with O2 it has been oxygenated then it is called Oxy – Hb.
  • Oxygen binding with Hb is a four step process; the O2 affinity of a particular heme is influenced by the oxygenation of other hemes in that haemoglobin molecule. These heme-heme interactions are responsible for the sigmoid shape of the oxyhemoglobin curve.
  • Greater the concentration of Hb in blood greater the amount of O2 carrying capacity.
  • At 150 mm Hg PO2, the blood is nearly saturated.

Last modified: Monday, 26 December 2011, 9:42 AM