Tag: functions and principal sources of lipids

Lipids are compounds of carbon, hydrogen and oxygen where ratio of hydrogen and oxygen is less than that of water. Lipids are esters of fatty acids and alcohol which form emulsion with water but are soluble in organic solvents. Some of the common examples of lipids are butter, ghee, cholesterol, carotene etc. Lipids are used as energy source. Lipids provide 9.3 kcal per gram as compared to 4.5 kcal per gram by carbohydrates. Lipids have other important uses also like they lubricate hairs and feathers in animals, reduce transpiration in plants and form components of cell membranes in organisms.

Unsaturated fatty acids have one or more double bonds like oleic acid (one), linoleic acid (two), linolenic acid (three), and arachidonic acid (four). An unsaturated fatty acid with one double bond is called mono unsaturated fatty acid (MUFA). Fatty acid with more than one double bond is called as polyunsaturated fatty acid (PUFA). Animals cannot synthesize fatty acids with double bonds (Linoleic, Linolenic and Arachidonic acids). Hence, these fatty acids must be obtained in diet and are thus called essential fatty acids.

Lipids are esters of fatty acids and glycerol which form emulsion with water are soluble in organic solvents, example- ghee, butter, carotene, menthol. Fatty acids are long chains of hydrocarbon having an acidic group. Chemically, lipids are diverse and may be acidic or esters but all lipids have a common property that they are hydrophobic and insoluble in water.

Lipids are hydrophobic means water-hating. They are water-insoluble. Lipids are non-polar molecules while water is a polar molecule, so there is no way for water to attach to a lipid molecule. Instead, the non-polar lipids will bind to themselves, which is why oils and fats form droplets on the surface of the water.

The average amount of protein present in muscle is 18.5%. Lipids constitute 3% in muscle

Respiration is the oxidation process in which reduced biomolecules like carbohydrates, fats, proteins etc are oxidised to release energy, which can be used for cellular processes. Fats are most reduced biomolecules and their oxidation releases maximum amount of energy. The energy released in oxidation of one gram of fat is twice the energy released in oxidation of one gram of carbohydrate. Hence, carbohydrates are used as an energy reserve biomolecules in living systems.

Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from sphingosine instead of glycerol. 

Lipids are hydrophobic means water hating. They are water insoluble. Lipids are non-polar molecules while water is polar molecule, so there is no way for water to attach to a lipid molecule. Instead, the non-polar lipids will bind to themselves, which is why oils and fats form droplets on the surface of water.