Functions of Lipids

Suaib Luqman

epgp books

 

  1. Objectives
  • v To understand the functions of lipids
  • v How they act
  • v What they do

 

  1. Concept Map
  1. Description

 

Lipids are natural hydrophobic molecules (organic compounds) occur all through the existing living organisms including plants, microbes, animals and also in each and every cell. Being a vital dietary component, lipids are a basis of high energy treasure, essential fatty acids and fat soluble vitamins. They dole out as an extremely greater cause of energy and accumulated in adipocytes. Lipids also function as an insulating material in the sub-cutaneous tissues and are also spotted in the region of certain organs. They participate in nerve cell functioning, cell structure built-up and supply stored fuel.

In addition to the above-mentioned characteristics, lipids execute numerous biological functions:

  • Act as storage compounds, TGs serve as stockpile energy of the body.

 

It is well-known that lipids perform a fundamental activity in the body (e.g. chemical messenger) than earlier described storage and cell membrane formation. Researchers have found that lipids have a pervasive activity in the body in provisos of hormonal regulation or intracellular signaling etc. They are blended through intricate biosynthetic pathways, yet deemed essential and ought to be complemented via diet. In 1929, George & Mildred Burr established that linoleic acid is an indispensable dietary component while Bergström et al. (1964) reported that prostaglandins originate from arachidonate that exert their effects on inflammation and allied disease condition. In 1979, platelet activating factor (earliest bioactive phospholipid) was revealed and awareness was heaved regarding the role of phosphatidylinositol and their metabolites in signaling and cell message transfer.

Lipids as Chemical Messengers

All the multicellular organisms utilize lipids as chemical messengers to propel information among cells, tissues and organs. Since lipids are water insoluble and diminutive, they are exceptional contender for signaling. The esterified forms of lipids penetrate membranes and are elated to transmit signals to the adjacent cells. After encountering the suitable receptor, lipids remains idle till they arrive at action site and bind to certain proteins to accomplish the deed.

 

Energy Storage

 

 

TAGs are storage lipids, indolent and consist up of a glycerol moiety and three fatty acids. TAGs release FFAs or non-esterified form of FAs to outline the cell structural components. Dietary FAs of small chain and average size are non-esterified, oxidized swiftly in tissues to serve as a fuel source. Elongated FAs are first esterified to structural lipids or TAGs.

 

Temperature Safeguarding

 

 

Sub-cutaneous fat beneath the skin layers too assist in protection from cold and insulation. Brown fat as divergent to white one primarily maintains body temperature. Children boast a superior brown fat level.

 

Membrane Formation

 

Lipids of membrane are equipped with PUFAs, an essential constituent of the phospholipids that bestow numerous essential membrane properties. Fluidity and flexibility of the membrane are the most imperative assets. EFAs (Linoleic and linolenic) form arachidonic, docosahexaenoic and eicosapentaenoic acids, in part required for membrane lipid formation.

Cholesterol formation

To a great extent, cholesterol is placed in the cell membranes; appear as plasma lipoprotein in the blood. Lipoproteins (lipids and proteins aggregates) facilitate the transport of lipids throughout the body and craft their movement feasible in an aqueous environment. Based on the relative densities, the major groups of lipoprotein are categorized as chylomicrons (CM), high density lipoproteins (HDL), low density lipoproteins (LDL) and  very low density lipoproteins (VLDL). Phospholipids (Phosphatidylcholine and Sphingomyelin) interact with cholesterol and maintain the fluidity of membranes. Cholesterol, in addition, is also the predecessor of bile acids, steroidal hormones and vitamin D.

 

Role in Prostaglandin formation and Inflammation

 

 

The EFAs (linolenic and linoleic acids) are predecessor of a lot of diverse types of eicosanoids such as prostanoids (thromboxanes, prostaglandins, prostacyclins), hydroxyeicosatetraenes, resolvins and leukotrienes (lipoxins) etc. that plays an imperative part in blood clotting, inflammation, fever and pain.

 

Lipids and Vitamins

 

 

The fat soluble vitamins (A, D, E, K) are vital nutrients with plentiful purpose. The metabolism of FAs has been carried out by Acyl-carnitines involving inward and outward operation by mitochondria. Polyprenols and their derivatives (phosphorylated) facilitate the transfer of molecules through membranes. Cardiolipins (a sub-type of glycerophospholipids with three glycerol groups and four acyl chains) activate enzymes involved with oxidative phosphorylation.

 

  1. Summary

 

In this lecture we learnt about:

 

  • The Functions of the lipids

 

 

you can view video on Functions of Lipids

 

Weblinks

 

 

Books

 

  1. Handbook of Functional Lipids by Casimir C. Akoh. 2005. https://books.google.co.in/books?isbn=1420039180
  2. The Lipid Handbook with CD-ROM, Third Edition by Frank D. Gunstone, John‎ L. Harwood, Albert‎ J. Dijkstra. 2007. https://books.google.co.in/books?isbn=1420009672
  3. Metabolism and Functions of Bioactive Ether Lipids by Akhlaq A. Farooqui, Tahira‎ Farooqui, Lloyd‎ A. Horrocks – 2008. https://books.google.co.in/books?isbn=0387774017
  4. https://en.wikibooks.org/wiki/Fundamentals_of…/Functions_Lipids
  5. Stryer L, Berg JM, Tymoczko JL (2007). Biochemistry (6th ed.). San Francisco: W.H. Freeman. ISBN 978-0-7167-8724-2.
  6. van Holde KE, Mathews CK (1996). Biochemistry (2nd ed.). Menlo Park, California: Benjamin/Cummings Pub. Co. ISBN 978-0-8053-3931-4.