Transport of oxygen & carbon dioxide
Every cell in your body needs oxygen and must get rid of carbon dioxide, and it is the red blood cell that carries both. In this lesson we see how haemoglobin loads oxygen in the lungs to form oxyhaemoglobin and unloads it in respiring tissues. We follow carbon dioxide back to the lungs by its three routes - mostly as hydrogencarbonate ions made by the enzyme carbonic anhydrase inside red blood cells, some as carbamino-haemoglobin, and a little dissolved in plasma - and see how haemoglobin buffers the hydrogen ions as haemoglobinic acid. We learn why carbon monoxide is so dangerous, forming carboxyhaemoglobin and lowering the blood's oxygen-carrying capacity. Then we draw and explain the sigmoid oxygen dissociation curve of adult haemoglobin, using cooperative binding to explain its S-shape and reading off loading in the lungs and unloading in the tissues. Finally we meet the Bohr shift, and see why humans make more red blood cells at high altitude.
By the end you should be able to (NSSCAS Biology (AS) 2.7.1b):
- Describe the role of red blood cells in carrying oxygen and carbon dioxide with reference to the role of: haemoglobin; carbonic anhydrase; the formation of haemoglobinic acid; the formation of carbamino-haemoglobin (details of the chloride shift are not required)
- Describe how carbon monoxide binds with haemoglobin to form carboxyhaemoglobin reducing the affinity of haemoglobin for oxygen
- Describe the role of plasma in the transport of carbon dioxide
- Describe and explain the oxygen dissociation curve of adult haemoglobin
- Explain the importance of the oxygen dissociation curve at partial pressures of oxygen in the lungs and in respiring tissues
- Describe the Bohr shift and explain the importance of the Bohr shift
- Describe and explain the significance of the increase in the red blood cell count of humans at high altitude
Miss Rachel and Mike talk through the whole topic — with the figure and working drawn live.