Myoglobin is a globular protein composed of 153 amino acids. It is single-chained and has an iron-containing porphyrin in the center. Myoglobin is found in heart and skeletal muscles. As oxygen is bound to myoglobin, the muscle is able to maintain a high level of activity for a longer period of time it, using up the oxygen when they contract during physical activities.
Myoglobin has a molecular weight of 16,700 daltons. It is structurally related to hemoglobin and is the primary oxygen-carrying pigment of muscle tissues. Myoglobin combines with oxygen to form oxymyoglobin, acting as a small oxygen store of about 10 millilitres per kilogram of muscle. This source of oxygen is important during intermittent bursts of activity. Oxymyoglobin restored during recovery periods. Muscle rich in myoglobin is called red muscle. It has a preponderance of slow-twitch muscle fibers and is adapted to endurance activities.
Myoglobin arranges itself in pigments, which are responsible for making meat red. The red color which meat takes is partly determined by the charge of the iron atom in myoglobin and the oxygen attached to it. When meat is in its raw state, the iron atom is in the +2 oxidation state, and is bound to a dioxygen molecule (O2). The structure of myoglobin was figured out by John Kendrew and associates in 1958, using high-resolution X-ray crystallography.