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.
Hemoglobin are little iron-based proteins. We have zillions of them in our blood, and they like to cluster into donut-shaped discs called red blood cells (or erythrocytes). Each hemoglobin has four binding sites where oxygen molecules like to attach. Each site can bind one oxygen, and only one.