section_path: Human physiology/Transport in the blood
section_name: Transport in the blood
paragraph_text: Transport in the blood
  
  CO is carried in blood in three different ways. Exact percentages vary between arterial and venous blood.
  
  Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO decreases the amount of oxygen that is bound for a given partial pressure of oxygen. This is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.