This occurs in many of the decomposition reactions of digestion. For a review of the following important macromolecules click here For the following discussion, the emphasis will be on relevance to microbiological systems. The fermentation products of various sugars are very useful in bacterial identification. All carbohydrates contain C, H, and O atoms. In living systems lipids are essential components of cell walls and membranes.
Lipids are nonpolar, hydrophobic molecules.
The cell walls of Archaea have unusual lipids in that they are connected by ether linkages. They consist of glycerol, two fatty acids and a phosphate group. Sterols are important components of plasma membranes of animal cells and a group of bacteria called Mycoplasma . Sterols all contain a characteristic 4- ring carbon system. This lipid barrier contributes to slow generation times and to the pathogenesis of these bacteria.