Simple Lipids are esters of fatty acid with farious alcohols.
Fats and Oils (Triglycerides)
- They constitute about 98% of total dietary lipids ; the remaining 2% consists of phospholipids and cholesterol and its esters.
- They are the major components of storage or depot fats in plant and animal cells but are not normally found in membranes.
- They are nonpolar, hydrophobic molecules since they contain no electrically charged or highly polar functional groups.
- In animals, the fat cells or adipocytes contain very large quantities of triglycerides in the form of fat droplets, which fill almost the entire cell volume.
- Adipocytes are abundantly found under the skin, in the abdominal cavity and in the mammary glands.
- Triglycerides can be stored in quantities, sufficient to supply the energy needs of the body for many months, as in the case of obese persons.
- Most fats and oils, upon hydrolysis, yield several fatty acids as well as glycerol.
- In a normal man, weighing 70 kg, at least 10-20% of the body weight is lipid, the bulk of which is triacylglycerol (TAG).
- Most animal fats such as those from meat, milk and eggs are relatively rich in saturated fatty acids but contain a rather low content of polyunsaturated fatty acids; two exceptions are chicken fat and fish fat.
- The plant fats contain a large proportion of unsaturated fatty acids (esp., polyunsaturated). The unsaturated fatty acids have low melting point and confer liquid state to the plant fats.
- A saturated fat consists of fatty acids with no carbon-carbon double bonds.
- An unsaturated fat has a double bond while a polyunsaturated fat has multiple double bonds.
- Essential fatty acids are fatty acids that have to be supplied in the diet
- Chemically, triglycerides are esters of glycerol with 3 fatty acid molecules as shown below:
- Biological waxes are esters of long-chain (C14 to C36) saturated and unsaturated fatty acids with long-chain (C16 to C30) alcohols.
- Their melting points (60 to 100 C) are generally higher than those of triacylglycerols.
- Waxes are unusually inert due to their saturated nature of the hydrocarbon chain.
- They can be split slowly with hot alcoholic KOH.
- They are insoluble in water and highly resistant to atmospheric oxidation.
- Most of the waxes are mixtures of esters.
- Biological waxes find a variety of applications in the pharmaceutical, cosmetic, and other industries.
- Lanolin (from lamb’s wool), beeswax, carnauba wax (from a Brazilian palm tree), and wax extracted from spermaceti oil (from whales) are widely used in the manufacture of lotions, ointments, and polishes.
- The shiny leaves of holly, rhododendrons, poison ivy, and many tropical plants are coated with a thick layer of waxes, which prevents excessive evaporation of water and protects against parasites.
- Triacontanoylpalmitate, the major component of beeswax, is an ester of palmitic acid with the alcohol triacontanol as shown below: