Red blood cells are made in the bone marrow, and their purpose is to carry oxygen round the body.
The bones that red blood cells are made in are the flat bones, such as the hip bone and the breast bone. Red blood cells have no central nucleus, so that they have a greater capacity to carry more oxygen around the body.
When the oxygen reacts with the protein haemoglobin that is found in blood, it forms oxy-haemoglobin, which is carried round the body, and the oxygen is deposited at each individual cell in the body. The equation for this reaction is:
##Hb+4O_2 rightleftharpoons Hb.4O_2##