The most prominent of these (and historically the first) is the representation theory of groups, in which elements of a group are represented by invertible matrices in such a way that the group operation is matrix multiplication.
hemoglobin is able to perform this function due to its ability to reversibly bind to oxygen. inside oxygen rich areas of the lungs, hemoglobin picks up oxygen molecules, then it transports the oxygen via red blood cells to bodys tissue, once hemoglobin reached the oxygen poor area of the tissues it releases the oxygen.
Oxygen is carried within red blood cells by a compound called hemoglobin, which is able to bind up to four oxygen molecules and form oxyhemoglobin. Each red blood cell contains large quantities of this molecule, allowing them to carry around far more oxygen than needed to ensure that supply always meets demand.