Peroxisomes are small (0.2–1 µm in diameter) membrane-bound Histopathology Department, Sheffield Teaching Hospitals, UK .)
organelles present in most mammalian cells. They contain more than
50 enzymes responsible for multiple catabolic and synthetic biochemi-
cal pathways, in particular the β-oxidation of very-long-chain fatty Mitochondria
acids (>C22) and the metabolism of hydrogen peroxide (hence the In the electron microscope, mitochondria usually appear as round or
name peroxisome). Peroxisomes derive from the endoplasmic reticu- elliptical bodies 0.5–2.0 µm long (Fig. 1.6), consisting of an outer
lum through the transfer of proteins from the endoplasmic reticulum mitochondrial membrane; an inner mitochrondrial membrane, sepa-
to peroxisomes by vesicles that bud from specialized sites of the endo- rated from the outer membrane by an intermembrane space; cristae,
plasmic reticulum and by a lipid non-vesicular pathway. All matrix infoldings of the inner membrane that harbour ATP synthase to gener-