COMPARTMENTS AND MEMBRANE STRUCTURE IN FREEZE-ETCHED HEART MUSCLE MITOCHONDRIA

Freeze-etched heart muscle mitochondria - in contrast to cell nuclei - do not expose the outer surface of the inner membrane. Fractured faces parallel to the outer membrane and across the inner membrane are compared with fractures through oil- and lecithin emulsions. The thickness and a decoration effect along the hydrophilic interface of bimolecular leaflets of lecithin correspond with those of the lipid component in membrane layers. Lecithin layers, however, show a higher degree of order than the lipid component of native membranes. It is suggested that a high concentration of enzymes in the outer compartment gives rise to the formation of a semi-solid gel in contrast to the liquid sols of other cell compartments. © 1969 Springer-Verlag.