Structure of Red and White Blood Cells
Compare the structure of the red blood cell and lymphocyte below (type of white blood cell).
Red blood cells are small and biconcave in shape as they lack a nucleus
and other organelles. This means the cell can be packed with haemoglobin,
the oxygen carrying pigment. The red blood cells are also flexible
so they can squeeze through the small capillaries.
White blood cells are larger than red blood cells, the lymphocyte
above has a very large nucleus and very little cytoplasm. The nucleus
appears large as the cell is undergoing cell division and so the
amount of genetic material has been doubled.