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Lipids - what are they?

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Lipids Lipids are fats, oils and waxes, organic compounds containing carbon, hydrogen and oxygen. The same three elements are involved in the structure of carbohydrates, but the amount of oxygen in the molecule present is much less than in carbohydrates. Lipids are insoluble in water but soluble in organic solvents such as acetone and ether. They are relatively small molecules compared to the polysaccharides, but because they are insoluble they tend to join together to form globules. Lipids can be split into the following They are glycerol, fatty acids, oils, fats, waxes, phospholipids and triglycerides (ester). The properties of the fats are, * Fats are insoluble in water but soluble in organic solvents. * Behave as water hating molecules ( hydrophobic molecules) * They are relatively small in size. * Fats are solids at room temperature Oils * Insoluble in water but soluble in organic solvents * They are relatively small in size * Behave as water hating molecules ( hydrophobic molecules) ...read more.


Fatty acids play an important role in cells. Fatty acids can be broken down and oxidized to release energy; they can also be converted into phospholipids, which are important constituents of cell membranes. Triglycerides are the commonest lipids in living organisms and their primary importance is as energy stores. As I have said they are compact and insoluble and can be stored at very high concentrations in cells (they do not have any osmotic effect on the cell), in cells they occur as small oil droplets suspended in the cytoplasm. Triglycerides release twice the amount of energy as per gram of carbohydrates, but also when triglycerides are broken down metabolic water is produced which is very important for animals that live in arid countries. (Metabolic water is water produced when organic molecules are oxidised in a reaction. Oils are the major food stores in many seeds (sunflower, rape) and fruits (palm, olive). ...read more.


Cholesterol molecules have different structure, but do have polar and non-polar regions. Cholesterol molecules are arranged in bilayer with their polar groups close to the polar groups of the other lipid molecules. Waxes are esters of fatty acids and long chain alcohols. In the living world wax is used as waterproofing for plants and animals, honey bees produce wax to make honey combs and the cells in which the eggs are to be laid and where the development of larvae takes place. The following are the uses of lipids in the living world * Food stores in seeds ---lipids are stored as food in seeds of plants i.e. sunflower * Insulation ---the adipose layer--- lipids insulate the body of animals (humans) from very cold weather. * Protect vital organs--- lipids tend to cover the vital organs of animals i.e. if there was an accident the vital organs will be saved (kidneys, heart) * Buoyancy in aquatic animals---lipids help aquatic animals (mammals i.e. see lions, whales, penguins and all kind of fishes) to float on water. ...read more.

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