unloaded oxygen into our cells.) And when
oxygen manages to rob the iron atom of an
electron and then escape, the iron atom loses
its ability to hold oxygen at all, has to settle
for a water molecule, and the myoglobin
becomes brown.
White and red muscle fibers. Fast muscle cells
are thicker than slow cells, contain little
oxygen-storing myoglobin pigment and few
fat-burning mitochondria. The thinness of
slow, red muscle fibers speeds the diffusion of
oxygen from the external blood supply to the
center of the fibers.
Each of these myoglobins — the red, the
purple, and the brown — is present in red
meat. Their relative proportions, and so the
meat’s appearance, are determined by several
factors: the amount of oxygen available, the