Hemoglobin is a protein that is carried by red cells. It picks up oxygen in the lungs
and delivers it to the peripheral tissues to maintain the viability of cells. Hemoglobin
is made from two similar proteins that "stick together". Both proteins must be
present for the hemoglobin to pick up and release oxygen normally. One of the component
proteins is called alpha, the other is beta. Before birth, the beta protein is not
expressed. A hemoglobin protein found only during fetal development, called gamma,
substitutes up until birth.