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Characteristics of Lipids

Lipids--the fats, oils and waxy substances consumed and digested for energy--are an essential part of the body's biochemical processes for energy and structure of cells. They are also the precursors to important biomolecules such as hormones. There are specific characteristics that make a lipid molecule, but each one is created from a basic compound called glycerol.

  1. The Template

    • Lipid molecules begin with a simple glycerol molecule. The glycerol molecule is dehydrated and bonded with long hydrocarbon chains. These two molecules joined together form what is known as a triglyceride.

    Soaps

    • Because of the hydrophobic nature of the fatty acid chains, lipids are used as soaps to grab dirt and wash it away. The head of the lipid molecule is water soluble while the tail is soluble in oil. The tails attach to oily dirt, and the head attaches to the water. This process is called emulsification, and it allows people to clean dirt off of objects with the use of lipids.

    Unsaturated and Saturated

    • Saturation is the term used to describe the carbon-carbon bonds present in a lipid molecule. Saturation also determines whether the fat molecule is a liquid or a solid at room temperature. Saturated lipid molecules have no double-bonds along the carbon skeleton. This type of chain forms compact structures that exist as a solid at room temperature. Unsaturated fatty acid chains have a "kink" from double-bond formations in the carbon skeleton. Because the fatty acids are not able to pack tightly together, this type of lipid is liquid at room temperature.

    Double Bonds

    • The double bonds in the carbon skeleton of lipids play an important role in its breakdown in the cells. It's popularly known that avoiding trans fats is essential for healthy living. The term "trans" refers to the way the hydrogen molecules are situated across the double bond in unsaturated fatty acids. Hydrogen molecules in trans fatty acids are situated on opposite sides of the molecule in three-dimensional space. Double bonds (the good fatty acid foods) are situated on the same side of the fatty acid chain. The positioning of these molecules is important in the breakdown of lipids in the mitochondria of cells.

    Other Lipids

    • Lipids have other structures that are used in the body. Replacing a fatty acid chain with a phosphate group creates the lipid bilayer, which is important in the structure of cell membranes. Steroids are lipid molecules with ring structures used in the synthesis of hormones.

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