Gas Transport - Oxygen

Oxygen transport

Red blood cells transport 90 percent of oxygen to peripheral tissues, carried on haemoglobin - 98.5 percent of oxygen bound to haemoglobin and 1.5 percent dissolve in plasma

Haemoglobin

Four globin protein chains - two alpha and two beta, each have a haem group with Fe2+ ion in the centre that attaches to oxygen, each haemoglobin can bind to four oxygens (reversible process)

Oxygen saturation

When all four haems in haemoglobin molecule are attached to oxygen = 100 percent saturation, saturation depends on partial pressure of oxygen (high pressure = high saturation) and affinity of haemoglobin to bind to oxygen

Relationship between haemoglobin saturation and partial pressure of oxygen

Sigmoid curve

Oxygen affinity

After binding with the first oxygen, haemoglobin changes shape to facilitate further uptake of oxygen = increased oxygen affinity

Effect of pH on oxygen affinity and dissociation

Lower pH = lower oxygen binding affinity (more likely for oxygen to be released), higher pH = higher oxygen binding affinity - oxygen dissociates when blood reaches the tissues

Effect of temperature on oxygen affinity and dissociation

Higher temp = lower oxygen binding affinity (more likely for oxygen to dissociate), lower temp = higher oxygen binding affinity, effect is significant in active tissues generating large amounts of heat

Oxygen release into tissues due to affinity

Released into tissues when oxygen affinity to haemoglobin is reduced due to peripheral tissue PO2 is less than arterial blood PO2, peripheral tissue PCO2 is more than arterial blood PCO2 (hypercapnia and acidosis) and when heat is produced in peripheral tissues