Identify the cells C, D and E.
Suggest why chronic lymphocytic leukaemia (CLL) begins in the bone marrow rather than elsewhere in the body.
Explain why a high white blood cell count is seen in measles and in CLL. Your answer should treat measles and CLL separately.
Describe and explain how oxygen passes across the cell surface membrane of the red blood cell.
At high altitude, the oxygen partial pressure in the atmosphere is lower than it is at sea level. If a person moves from low altitude to high altitude and stays there for several weeks, the red blood cell count rises. Explain why the body must respond to high altitude by increasing the number of red blood cells.
Before a red blood cell enters the circulation, polypeptide synthesis has already taken place. The $HBB$ gene codes for the $\beta$-globin polypeptide of haemoglobin. There are two alleles of $HBB$, called $Hb^A$ and $Hb^S$. Describe the difference between the $Hb^A$ allele and the $Hb^S$ allele and state how this difference affects: • the $\beta$-globin polypeptide • the haemoglobin molecule.