Question

Describe various forms of lipid with a few examples.

Answer 1

Lipids are generally water-insoluble. They could be simple fatty acids. A fatty acid has a carboxyl group attached to an R-group. The R-group could be a methyl (–CH₃), or ethyl (–C₂H₅) or a higher number of CH₂ groups (1 carbon to 19 carbons). For example, palmitic acid has 16 carbons including carboxyl carbon. Arachidonic acid has 20 carbon atoms including carboxyl carbon. Fatty acids could be saturated (without a double bond) or unsaturated (with one or more C=C double bonds). Another simple lipid is glycerol which is trihydroxy propane.

• Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They can be then monoglycerides,
  diglycerides and triglycerides. These are also called fats and oils based on melting point. Oils have a lower melting point (e.g., gingerly oil) and hence remain as oil in winter.
• Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found in cell membranes. Lecithin is one example. Some tissues especially the neural tissues have lipids with more complex structures.