Lipids and their role in living organisms.

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Lipids and their role in living organisms

Hyung-woo (Shane) Cho

Even though there is no widely accepted definition for Lipids, they usually defined as a large and varied group of organic compounds. Apart from glycerol, they are insoluble in water, but soluble in organic solvents such as ethanol and ether. All lipids contain the elements carbon, hydrogen and oxygen with the ratio of H : O is greater than 2:1, have a lower proportion of oxygen compared to carbohydrates. This of these extra hydrogen atoms, lipids are denser than carbohydrates, which makes lipids to have more chemical potential energy than carbohydrates.

Generally, lipids exist as

  • Fats and oils
  • Waxes
  • Steroids
  • Phospholipids

In these types of lipids, fats and oils are the most common types, that are formed when three fatty acid molecules bond with a glycerol. Fats are often found in animals and are solid at room temperature. They are known as saturated fatty acids. On the other hand, oils are liquid at room temperature because the fatty acids in oils are smaller than those in fats, and because of the presence of one or more double bonds in some oils (unsaturated). Oils are generally found in plants and in some animals such as fish livers. Fats and oils are sources of energy and metabolic water to living things, a buoyancy aid (blubber) in aquatic mammals, waterproofing for hair and feathers, and an electrical insulation around the axons of neurons.

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Commonly lipids are made of two parts, glycerol and fatty acids. One of the examples of lipids is triglyceride. When a glycerol molecule is attached with one fatty acid, it is called monoglyceride. If it is attached with two fatty acids, it is called diglyceride, with three fatty acids, triglyceride forms. A condensation reaction produces a triglyceride and water molecule when glycerol and three fatty acids react together. As seen on the diagrams below, each hydrogen atom at the right of the glycerol is bonded to a hydroxyl (-OH) group. This releases water, and ester bond is formed, which is called ...

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