Hemoglobin is an oxygen-carrying pigment in red blood cells that transports oxygen from the lungs to tissues throughout the body. This process is an example of chemical bonding, as hemoglobin attracts and binds to oxygen molecules. Factors like pH and blood doping procedures can impact hemoglobin's ability to carry oxygen. Blood doping in sports aims to enhance performance by increasing red blood cell count and oxygen transport, but it poses medical risks like thickened blood and blood clots.