Lipids 1.1: Some types of lipids and their function

Fatty acids

These are the defining constituents of lipids and are in large part responsible for the distinctive physical and metabolic properties. They are also important in non-esterified form.

In the body these are released from triacylglycerols during fasting to provide a source of energy.

Linoleic and linolenic acids are essential fatty acids, in that they cannot be synthesised by animals and must come from plants via the diet. They are precursors of arachidonic, eicosapentaenoic and docosahexaenoic acids, which are vital components of all membrane lipids.

Fatty acids in diet are short and medium chain length are not usually esterified. Once within the body they are oxidized rapidly in tissues as a source of ‘fuel’.

Longer chain fatty acids are usually esterified first to triacylglycerols or structural lipids in tissues.

Triacylglycerols

These form the primary storage form of long chain fatty acids for energy and structure formation of cells. These are composed of glycerol (1,2,3-trihydroxypropane) and 3 fatty acids to form a triester. Triglycerides are found in blood tests. Complete hydrolysis of triacylglycerols yields three fatty acids and a glycerol molecule.  Polyunsaturated fatty acids are important as constituents of the phospholipids and form the membranes of the cells. Most of the natural fats and oils of commerce consist of triacylglycerols

Tri-, Di- and Monoacylglycerols

1,2-Diacylglycerols are formed as intermediates in the biosynthesis of triacylglycerols. These also function as second messengers in many cellular processes. Monoacylglycerols are produced when triacylglycerols are digested in the intestines of animals.

Sterols

Cholesterol is a ubiquitous component of all animal tissues. Most of it is present in the membranes. It occurs in the free form and esterified to long chain fatty acids (cholesterol esters) in animal tissues, including the plasma lipoproteins. Cholesterols are precursor of bile acids, vitamin D and steroidal hormones.

 

ref: http://www.elmhurst.edu/~chm/vchembook/620fattyacid.html

Lipids 1.0: Introduction

Lipids Introduction

The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in nonpolar organic solvents (e.g. ether, chloroform, acetone & benzene) and general insolubility in water. There is great structural variety among the lipids, as will be demonstrated in the following sections.

Most people think of lipids negatively because they associate them with fats. Although some lipids are classified as fats, lipids are not “bad.” On the contrary, they provide very important functions in the body.

Fats are composed of fatty acids and glycerol. They store energy, help to insulate the body, and cushion and protect organs. Phospholipids contain two fatty acids and are a major component of cell membranes. Steroids are cholesterol derived hormones that regulate various physiological functions in the body.

ref: http://www.news-medical.net/health/What-are-Lipids.aspx

Lipids 1.3: Structure Function Animation

Short and to the point!
ref:http://www.youtube.com/watch?v=ESPNqKUluRs

Lipids 1.2: Phospholipids

Phospholipids

Phospholipids belong to the lipid family of biological polymers. A phospholipid is composed of two fatty acids, a glycerol unit, a phosphate group and a polar molecule. The phosphate group and polar head region of the molecule is hydrophillic (attracted to water), while the fatty acid tail is hydrophobic (repelled by water). When placed in water, phospholipids will orient themselves into a bilayer in which the non-polar tail region faces the inner area of the bilayer. The polar head region faces outward and interacts with the water.

Phospholipids are a major component of cell membranes which enclose the cytoplasm and other contents of a cell. Phospholipids form a lipid bilayer in which their hydrophillic head areas spontaneously arrange to face the aqueous cytosol and the extracellular fluid, while their hydrophobic tail areas face away from the cytosol and extracellular fluid.

 

ref: http://bioweb.wku.edu/courses/biol115/wyatt/biochem/lipid/Lipid_2.asp