Myoglobin

Myoglobin is a heme-containing protein in muscle cells that binds oxygen and helps make oxygen available for cellular metabolism. Its chemical state strongly influences the red, purple, or brown color of meat.

Heme: An iron-containing molecular group that binds gases and participates in electron-transfer reactions. Its iron atom is the site where myoglobin binds oxygen.
Globin fold: A protein structure of eight alpha helices that forms the framework of many heme-binding globins. This fold encloses myoglobin’s heme and shapes its oxygen-binding pocket.
Rhabdomyolysis: A syndrome in which damaged skeletal muscle releases intracellular contents into the bloodstream. Released myoglobin can contribute to kidney injury in severe cases.
Neuroglobin: A globin protein expressed mainly in nervous tissue and associated with cellular responses to oxygen stress. It is a tissue-associated globin like myoglobin, but occurs chiefly in nervous tissue.
Oxygen binding: The reversible association of oxygen molecules with proteins or other molecules. Myoglobin binds oxygen reversibly, storing a limited supply in muscle.
Hemoglobin: A red-blood-cell protein that transports oxygen through the bloodstream using four heme-containing subunits. Comparing it with myoglobin reveals the difference between oxygen transport and muscle storage.
Myoglobinuria: The presence of myoglobin in urine, usually following substantial muscle breakdown. It can signal that muscle-derived myoglobin has entered the circulation and passed into urine.
Cytoglobin: A globin protein found in many cell types and associated with intracellular oxygen and redox processes. Its broad tissue distribution contrasts with myoglobin’s strong association with muscle.
Oxymyoglobin: The bright-red form of myoglobin with oxygen bound to its heme iron. It produces the vivid red color of freshly oxygenated meat.
Muscle fiber: An elongated muscle cell containing contractile proteins and the machinery for energy production. Myoglobin resides inside these cells, near sites of oxygen use.

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