What is Lipids: Lipids are the structural and functional building blocks of the living cells and they are made up of hydrocarbons with the highly reduced form of carbon. Chemically they are a heterogeneous group of compounds related to fatty acids.

Examples: Fats, oils, waxes, etc.

Source of Lipid:

Lipids are a wide-ranging group of organic compounds found in all living organisms, including humans, plants, and other animals. It exists in tissues in many different physical forms. The simple lipids are often part of large aggregates in storage tissues, such as oil bodies or adipose tissue. Membranes are constituted with complex lipids and occur in a close association with such compounds as proteins and polysaccharides. In plants, the lipid is stored in the form of triglycerides. The most known of these is jojoba, which stores its seed lipid as a liquid wax. Storage lipid is accumulated in one or both of the main types of seed tissue and endosperm. In oilseeds such as sunflower, linseed, or rapeseed, the cotyledons of the embryo are the major sites of lipid accumulation. The endosperm of castor bean, coriander, or carrot, is the main site of lipid accumulation. In tobacco, both embryo and endosperm tissues store lipids. Phospholipids are another class of lipids that are found in animal and plant cell membranes.


  1. They are hydrophobic or amphiphilic compounds.
  2. They are insoluble in water but soluble in organic solvents like chloroform.
  3. When metabolized, lipids are oxidized to release large amounts of energy and thus are useful to live organisms.


  1. They are organic compounds formed mainly from alcohol and fatty acids combined by ester linkage.
  2. They are hydrophobic small molecules consisting of two biochemical subunits like keto acyl (Polyketides) and isoprene (C5H8) (Sterol lipids and Prenol lipids).
  3. Triglycerides are the most commonly occurring class of lipids.
  4. Triglycerides have a glycerol backbone bonded to three fatty acids.
  5. Phospholipids also contain glycerol and fatty acids, plus phosphoric acid and a low molecular-weight alcohol.
  6. Common phospholipids include lecithins and cephalins.
  7. The tail of fatty acid is a long hydrocarbon chain, which is hydrophobic, and the head of the molecule is a carboxyl group, which is hydrophilic.


  1. They are important sources of metabolic energy (ATP). They are the most energy-rich of all classes of nutrients.
  2. They form the structural components of cell membranes and form various messengers and signaling molecules within the body.
  3. Its serve as biological carriers for the absorption of fat-soluble vitamins A, D, E, and K.
  4. They are a source of essential fatty acids, which are required for optimal lipid transport and are precursors of prostaglandin hormones.
  5. Lipids function as mechanical support for the vital body organs.
  6. They are a source of essential steroids, which in turn perform a wide range of important biological functions.
  7. It also act as lubricants for the passage of feed through the pellet diet.
  8. They are applied in the cosmetic and nanotechnology.

Classification of Lipids:

They are broadly classified into three groups. They are listed in Fig.1.

Classification of lipids
Fig.1: Classification of lipids
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