Cell Membrane Structure and Function

... Cell membrane structure and function The total thickness of the membrane is about 7.0 nm. It is made of three layers, as seen on the light microscope, two dark and a lighter one separating them. The two dark layers are caused by the deposition of heavy metal on both sides of the membrane during the staining process, and the light region between is lipid. Beyond the plasma membrane of animal cells, there is a glycoprotein coat of different thicknesses. Cells that touch each other are separated by this intercellular material. When materials flow in and out of cells they pass through the glycoprotein coat. In phospholipids, the long hydrocarbon chains which project from the glycerol part of the molecule are insoluble in water whereas the glycerol end is soluble because it contains polar groups. When such a lipid is allowed to spread on a surface of pure water, the water soluble ends of the lipid

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