Red blood cells. Coloured scanning electron micrograph (SEM) of numerous red blood cells (erythrocytes). These biconcave, discshaped cells transport oxygen from the lungs to all the cells of the body. The oxygen is metabolized in aerobic respiration, producing energy, carbon dioxide and water. The carbon dioxide is transported back to the lungs by the red blood cells, where it is exhaled. The oxygen and carbon dioxide bind with haemoglobin, a protein compound that is found in red blood cells. Haemoglobin gives blood its red colour. Red blood cells are the most abundant cell in human blood. Magnification: x420 at 6x7cm size.
