What are lipids?
Whatmost people think when someone mentions lipids is 'ugh, fat', butthis is only partially true. Lipids are a group which encompassesthree similar kinds of the chemical compounds - fats, waxes and sterols.And many of these are essential for proper functioning of theorganism. Lipids are not soluble in water, are composed of carbon andhydrogen atoms, and play a pivotal role to the structure and functionof cell membranes. Read on to see what this is all about.
Human bodyobtains energy from oxidative breaking of compounds such ascarbohydrates, fats and proteins. Fats are also used as long – termenergy storage units. Fat deposits also serve as insulation, as theykeep the body warm by preventing the body heat to escape and the coldto penetrate in the body (remember how marine animals in the arcticcircle are fat). And stored fat is just a bunch of lipids stacked infat cells.
Lipids arepresent not only in animals, but in plants as well. Oil that we getfrom various plants for, in example, use in our cuisine or in beautycare products is a lipid. Lipids are excellent for energy storage asthey can store more energy per unit of mass than carbohydrates andproteins. Lipids can provide body with energy while there is littleor no food available, provided that there is enough water available.You can live without food for days or weeks on end if you havesufficient fat reserves. In example, animals that hibernate in thewinter or migrating birds, which fly hundreds and thousands of mileswithout eating survive solely on fat reserves.
As we mentioned,there are several groups of lipids. Triglycerides are compounds whichare found in the cell cytoplasm and serve for energy storage. Theseare made when one molecule of a complex alcohol known as glycerolreacts with three molecules of fatty acids. Structure of atriglyceride resembles a trident, glycerol is its base while fattyacids its spikes. Difference in chemical structure determines whethertriglycerides will stay liquid or solidify at 20ºC. Solid compoundsare commonly called fats while liquid compounds are called oils.
Phospholipidsare complex lipids, composed of molecules of different properties, sothat one side of them is water - attracted while the other is water -repelling. This unique property of phospholipids makes them the chiefbuilding substance in cell walls.
Lipoproteins aremolecules composed of lipids and proteins. Enzymes, antigens andstructural proteins are lipoproteins. There are two kinds of them:HDL (High Density Lipoproteins) and LDL (Low Density Lipoproteins).Lipoproteins allow the water – repelling fat to travel in the water– rich blood.
Waxes arecomposed of fatty acids and long chain alcohols. Wax function is toform a protective semipermeable layer for the cells. They are foundin both plants and animals.