Haemoglobin is a globular protein that contains haem groups. Explain how the presence of haem groups enables the haemoglobin molecule to transport oxygen.
At certain times, for example during intense exercise, a person may breathe very rapidly and deeply. This is called hyperventilation. Hyperventilation leads to more carbon dioxide being exhaled. Consequently, the concentration of carbon dioxide in the blood passing through the capillary network in respiring tissues is lower. This raises the affinity of haemoglobin for oxygen so that there is less release of oxygen from red blood cells. Explain why a lower concentration of carbon dioxide in the blood passing through respiring tissues causes less oxygen to be released from red blood cells.
Fig. 2.1 shows a diagram of a section through the heart. Describe and explain how the tunica media (middle layer of the wall) of blood vessel X adapts the blood vessel for its function.
Describe the role of the atrioventricular node (AVN) and the Purkyne tissue in the cardiac cycle.