Membranes
By electron microscopy, membranes appear as dark lines, due to the reaction of osmium with the membrane lipids. At much higher magnification, membranes show a trilaminar appearance due to the localized binding of electron-dense osmium within the lipid bilayer. Membranes are a component of many intracellular organelles, as well as forming the unique membrane at the cell surface, called the plasma membrane. The margins of two cells are visible in this image. 15,000x
Plasma membrane >
The plasma membrane is the membrane at the cell surface, enclosing the cytoplasm of the cell.
Cytoplasm
The plasma membrane is the membrane at the cell surface, enclosing the cytoplasm of the cell.
Nuclei >
A portion of the nucleus of each cell is visible.
Nuclear envelope >
Two membranes surround each nucleus, forming the nuclear envelope. Red arrows indicate the outer nuclear membrane; green arrows the inner membrane. Intracellular membranes, like the plasma membrane, are unit membranes.
RER >
Rough endoplasmic reticulum forms flattened sacs composed of unit membranes. RER membranes possess ribosomes on their cytoplasmic surface.
Mitochondria >
Intracellular membranes also form mitochondria which consist of two unit membranes. The inner membrane is folded inwards forming cristae.
Intercellular space >
The intercellular space contains numerous cellular extensions.
Cellular extensions
The intercellular space contains numerous cellular extensions.
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