BRAINCAKEOxygen Loading and Unloading
Haemoglobin picks up oxygen in one place and releases it in another. The amount of oxygen it holds depends mainly on the partial pressure of oxygen (pO2) around it.
Loading (association) in the lungs: in the alveoli, pO2 is high. Oxygen diffuses from the alveoli into the blood plasma and then into the red blood cells, where it combines with haemoglobin to form oxyhaemoglobin. Haemoglobin has a high affinity for oxygen at high pO2, so it becomes almost fully saturated.
Because oxygen is bound to haemoglobin, the concentration of free (dissolved) oxygen in the red blood cell stays low. This maintains a steep concentration gradient, so oxygen keeps diffusing in from the alveoli.
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Key terms in this lesson
- partial pressure
- The pressure that a particular gas in a mixture would exert if it alone occupied the whole volume.
More in Transport in Animals
- Electrocardiograms
- Aortic Aneurysms
- Red Blood Cells
- Haemoglobin
- The Oxygen Dissociation Curve
- Partial Pressure of Oxygen
- The Bohr Effect
- Fetal Haemoglobin
All 32 lessons in Transport in Animals · All OCR AS-level Biology topics