Transport of gases in the bloodEdexcel A-Level Biology B: Mind map

Exam questions on Transport of gases in the blood

1. Adult haemoglobin is a protein made of four polypeptide chains. Each chain contains a haem group with one iron(II) ion at its centre. Experiments show that the oxygen dissociation curve of haemoglobin is S-shaped, because the first oxygen molecule binds slowly but later molecules bind more easily.
   Explain why the oxygen dissociation curve of haemoglobin is S-shaped.2 marks
2. During vigorous exercise the muscle cells of an athlete respire rapidly. The partial pressure of carbon dioxide in the muscle capillaries rises and the pH of the blood in the capillaries falls. The oxygen dissociation curve of the haemoglobin in these capillaries changes position.
   Explain how the rise in carbon dioxide concentration in the muscle capillaries causes oxygen to be released from haemoglobin more readily.2 marks
3. Seals dive for long periods without breathing. Their muscles contain a very high concentration of myoglobin. Myoglobin is a single polypeptide with one haem group. At a partial pressure of oxygen of 2 kPa, myoglobin is more than 80% saturated with oxygen, whereas adult haemoglobin is only about 25% saturated.
   Compare the structure and function of myoglobin with those of adult haemoglobin.3 marks