The Role of Lipids In Living Organisms

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The Role of Lipids in Living Organisms

Lipids can be defined as “a group of substances that contain carbon, hydrogen and oxygen, as do carbohydrates, but in lipids the proportion of oxygen is much less.”(1) They are also defined as “hydrophobic (insoluble in water) yet are soluble in organic solvents like ethanol, chloroform and ether”(2). Lipids are a diverse group of organic compounds and so can be classified as:

  1. “Simple lipids, the animal fats, the vegetable oils and the waxes
  2. Complex lipids
  3. Phospholipids and related compounds
  4. Steroids”(2)

“Tryglycerols are formed by a condensation reaction that takes place between glycerol (an alcohol) and monocarboxylic acids (fatty acids)” The result of this reaction gives rise to a molecule of triglycerol and is used by living organisms as a source of energy store. When broken down lipids in the form of tryglycerols yield “38 kJg-1 of energy which is twice as much as the amount of energy that carbohydrates yield, 17kJg-1”(3). Another reason for using lipids as an energy store as oppose to carbohydrates is that lipids are more compact and insoluble in water. They are more compact because lipids, “tend to be only minimally  and, in turn, clumps of lipids () take up even less volume (and mass) than storage carbohydrates”(4)

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The role of tryglycerols goes beyond energy storage. Tryglycerols, commonly known as fat in animals and oils in plants is used to aid buoyancy of aquatic vertebrates such as sharks, seals and whales. This is done because lipids are less dense than water. “Sharks have extremely fatty livers which make up to 25% of their body volume and contain a lipid, squaline, with a specific gravity of only 0.86.”(2)  

Animals such as kangaroos, camels and rats also use fats to provide themselves with “metabolic water”. “When fats are oxidised in respiration water is produced and is used by the ...

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