Delivery of Oxygen to Cells Higher Human Biology Chapter 21

Haemoglobin Haemoglobin is a respiratory pigment which combines with oxygen and significantly increases the oxygen-carrying capacity of the blood. It consists of haem (a compound containing iron) and globin (a protein made of several polypeptides). A molecule of haemoglobin contains 4 haem groups each able to carry a molecule of oxygen.

Haemoglobin molecule showing the 4 haem groups.

Association and Dissociation To be effective a respiratory pigment must be able to combine easily (associate) with oxygen when the oxygen concentration in the surroundings is high and rapidly release (dissociate) oxygen when the surrounding oxygen concentration is low. Haemoglobin has a HIGH AFFINITY for oxygen when the oxygen concentration in the surrounding environment is high (e.g. lungs) and a LOW AFFINITY for oxygen when the oxygen concentration is low (e.g. active cells).

The Combining of Haemoglobin with Oxygen This chemical reaction is reversible Association (in lungs) Haemoglobin + oxygen oxyhaemoglobin Dissociation (in tissues)

Oxygen Dissociation Curve

The Effect of Temperature

Significance Large quantities of energy is generated by inflamed tissues suffering microbial infection. The rise in temperature that occurs locally in these tissues triggers the release of extra oxygen from haemoglobin. This is advantageous since these cells are exactly where extra oxygen is required for aerobic respiration.

Fetal Haemoglobin

THEY ARE PRODUCED IN THE BONE MARROW FROM STEM CELLS AND LAST FOR 120 DAYS. THEY REQUIRE IRON FOR THEIR FORMATION. THEY REQUIRE VITAMIN B12 FOR THEIR FORMATION. LACK OF IRON OR B12 RESULTS IN ANAEMIA. INTRINSIC FACTOR SECRETED BY THE STOMACH IS REQUIRED TO AID B12 ABSORPTION. LACK OF INTRINSIC FACTOR RESULTS IN PERNICIOUS ANAEMIA. RED BLOOD CELLS

Biconcave Shape of Red Blood Cells

HEALTHY RED BLOOD CELLS (the actual size of a red blood cell is approx 2 micron at the rim by 7 micron in diameter)

RED BLOOD CELL PRODUCTION OF RED BLOOD CELLS.

Production of Red Blood Cells Red blood cells are produced in the red bone marrow. Red bone marrow consists of stem cells

Red Bone Marrow

Destruction of Red Blood Cells A red blood cell lives for about 120 days Worn out red blood cells are destroyed by macrophages by the process of phagocytosis in the liver, bone marrow and spleen. Haemoglobin molecules are broken down and the iron stored for future use. The haem group (minus the iron) are converted to bilirubin.