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Introduction, Classification, Chemical Nature and Biological Role of Lipids

The term "lipid" encompasses a variety of organic compounds that do not interact particularly with water, including fats, hormones and oils.



The term "lipid" encompasses a variety of organic compounds that do not interact particularly with water, including fats, hormones, oils, and certain components of membranes. In addition to serving as energy storage depots, adipose cells provide thermal insulation. Some lipids, such as steroid hormones, act as communication channels between multiple types of cells or between systems within one cell. It is composed of two layers of phospholipid molecules that form the membranes of cells and organelles. A cell's membrane separates the cell from its surroundings and compartmentalizes its interior into structures that serve specific functions. Membranes, and the lipids that form them, play such a vital role in compartmentalizing that they must have been crucial for the origin of life.


It is possible to classify lipids based on their hydrolysis products, as well as on similarities in their molecular structure. They fall into three main groups:

1. Simple lipids

  • Oils and fats hydrolyze to produce fatty acids and glycerol.
  • When waxes are hydrolyzed, they yield fatty acids and long-chain alcohols.

2. Fats and oils

  • The triacylglycerols in both types of compounds are esters, which are made up of three fatty acids bound together by glycerol, trihydroxy alcohol.
  • At room temperature, they differ based on their physical states. Lipids are usually referred to as fats or oils, depending on how solid they are at 25°C and how liquid they are.
  • Different degrees of unsaturation are reflected in different melting points.

3. Waxes

  • Wax is created when long-chain alcohol (usually mono-hydroxy) is esterified with a fatty acid.
  • Acids and alcohols generally found in waxes usually have chains that have between 12 and 34 carbon atoms.

4. Conjugated lipids

  • As a result of hydrolysis, amino alcohol sphingosine, nitrogen-containing alcohol, glycerol, phosphoric acid, and phospholipids yield fatty acids. Based upon the alcohol group present (sphingosine or glycerol), they can either be glycerophospholipids or sphingophospholipids.
  • As a result of hydrolysis, glycolipids produce fatty acids, sphingosine, and glycerol, as well as carbohydrates. The glycerol or sphingosine alcohol group may render them glyceroglycolipids or sphingoglycolipids.

5. Derived lipids

The resulting products of lipid hydrolysis are known as derived lipids. Fatty acids, glycerol, sphingosines, and steroid derivatives make up these substances. It is important to note that steroid derivatives are phenanthrene structures that differ significantly from lipids formed from fatty acids.

Chemical nature

  • It is possible to have liquid or non-crystalline solid lipids at room temperature.
  • Pure fat or oil won't have any color, odor, or taste.
  • Their organic molecules are full of energy.
  • It is insoluble in water
  • Inorganic solvents such as chloroform, acetone, alcohol, and benzene are soluble in it.
  • There are no ionic charges
  • The proportion of saturated fatty acids in solid triglycerols (Fats) is high.
  • Unsaturated fatty acids are present in high concentrations in liquid triglycerols (oils).

Biological role

Various studies have established that lipids play an extremely important role in a cell's normal function. In addition to serving as highly reduced energy storage forms, lipids are also integral to cellular membranes and organelle membranes. The following are some of the functions of lipids:
  • They store a large number of energies.
  • Biological Membrane Production
  • Insulating
  • for Plant Leaves - e.g., preventing the leaves from drying
  • Causing buoyancy
  • acts as a hormone
  • Providing a hydrophobic barrier that prevents aqueous contents from leaking out of cells and subcellular structures acts as structural components of the body.
  • An animal's energy comes mainly from lipids, as do seeds that contain a lot of lipids.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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