According to Robertson, the unit membrane consisted of a bimolecular lipid leaflet sandwiched between outer and inner layers of protein organized in the pleated sheet configuration. Such an arrangement was presumed to be basically the same in all cell membranes. In the late 1950s, electron microscopy provided additional information about the structure of the plasma membrane. J. D. Robertson was [...]
The fatty acids are an important and also abundant group of lipids. In cells, the fatty acids only sparingly occur freely; instead, they are esterified to other components and form the saponifiable lipids. A fatty acid molecule may be either saturated or unsaturated. The saturated fatty acids consist of long hydrocarbon chains terminating in a carboxyl group and conform to [...]
The polysaccharides (or glycans) are composed of long chains of sugars and can be divided into two main functional groups the structural polysaccharides and the nutrient polysaccharides. The structural polysaccharides serve primarily as extracellular or intercellular supporting elements. Included in this group are cellulose (found in plant cell walls), mannan (found in yeast cell walls), chitin (in the shells of [...]