Steer anatomy and cuts of beef The shoulder, arm, and leg most of the work of supporting the animal They therefore contain a large proportion of reinforcing connective tissue, are tough, and best cooked thoroughly for an hour or more to dissolve the connective-tissue collagen into gelatin The rib, short loin, and sirloin less work, are generally the tenderest cuts, and are tender even when cooked briefly to a medium doneness Red Muscle Fibers Red muscle fibers are used for prolonged efforts They are fueled primarily by fat, whose metabolism absolutely requires oxygen, and obtain both fat (in the form of fatty acids) and oxygen from the blood Red fibers are relatively thin, so that fatty acids and oxygen can diffuse into them from the blood more easily They also contain their own droplets of fat, and the biochemical machinery necessary to convert it into energy This machinery includes two proteins that give red cells their color Myoglobin, a relative of the oxygen-carrying hemoglobin that makes blood red, receives oxygen from the blood, temporarily stores it, and then passes it to the fat-oxidizing proteins And among the fat oxidizers are the cytochromes, which like hemoglobin and myoglobin contain iron and are dark in color The greater the oxygen needs of the fiber, and the more it’s exercised, the more myoglobin and cytochromes it will contain The muscles of young cattle and sheep are typically 0.3% myoglobin by weight and relatively pale, but the muscles of the constantly moving whale, which must store large amounts of oxygen ... oxygen from the blood, temporarily stores it, and then passes it to the fat-oxidizing proteins And among the fat oxidizers are the cytochromes, which like hemoglobin and myoglobin contain iron and are dark in color... myoglobin contain iron and are dark in color The greater the oxygen needs of the fiber, and the more it’s exercised, the more myoglobin and cytochromes it will contain The muscles of young cattle and sheep are typically 0.3%...fat (in the form of fatty acids) and oxygen from the blood Red fibers are relatively thin, so that fatty acids and oxygen can diffuse into them from the blood more easily They also contain their own droplets of fat, and the