On Food and Cooking

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