Lipids Simplified: Introduction, Classification& Function

Pharmacy
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Introduction

Lipids may be regarded as organic substances relatively insoluble in water, soluble in organic solvents(alcohols, ether, etc), actually or potentially related to fatty acids & utilized by the living cells.

Definition - Any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, & steroids.

Classification of lipids

Lipids are broadly classified into simple, complex, derived & miscellaneous lipids, which are further subdivided into different groups.

  1. Simple lipids: Esters of fatty acids with alcohols. These are mainly of two types

a) Fats & oils(triacylglycerols): These are esters of fatty acids with glycerol.

b) Waxes: Esters of fatty acids with alcohols other than glycerol. These alcohols may be aliphatic or alicyclic. Cetyl alcohol is most commonly found in waxes.

  1. Complex lipids: These are esters of fatty acids with alcohols containing additional groups such as phosphate, nitrogenous base, carbohydrate, protein, etc. They are further divided as follows.

a) Phospholipids: They contain phosphoric acid & frequently a nitrogenous base.

b) Glycolipids: These lipids contain fatty acids, carbohydrate & nitrogenous base. The alcohol is sphingosine; hence, aka glycosphinolipids. Glycerol & phosphate are absent, e.g., cerebrosides, gangliosides.

c) Lipoproteins: Macromolecular complexes of lipids with proteins.

  1. Derived lipids: These are derivatives obtained on the hydrolysis of group 1 & 2 lipids, which possess the characteristics of lipids. These include glycerol & other alcohols, fatty acids, mono-and diacylglycerols, lipids, soluble vitamins, steroids, hormones, hydrocarbons & ketone bodies.
  2. Miscellaneous lipids: These include a large number of compounds possesing the characteristics of lipids, e.g., carotenoids, squalene, terpenes, etc.

Functions of lipids:

  1. They are the concentrated fuel reserve of the body(triacylglycerols).
  2. They serve as a source of fat-soluble vitamins(A, D, E & K).
  3. They are constituents of membrane structure & regulate the membrane permeability(phospholipids & cholesterol).
  4. Lipids are an important source of cellular metabolic regulators(steroid hormones & prostaglandins).

MBH/AB

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Absolutely, Lipids are stored in adipose tissue provide long term energy. They also act as a signaling molecules and generate secondary messengers like IP3 and DAG during hormonal response. Lipids play significant roles in daily life by powering energy needs.

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This article provides an overview of lipids , classification and functions in a very insightful manner.

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