In the cis configuration, the hydrogens on the carbons involved in the double bond are on the same side of the bond, whereas in the trans configuration, the hydrogens are located on the opposite sides. Unsaturated fatty acids can occur in two configurations: cis and trans. This will be called 18:3 Δ 9, 12, 15 according to the carboxyl referencing system and 18:3 (ω-3) according to the omega referencing system. The omega referencing system counts the position of the double bond closest to the omega carbon, with the omega carbon numbered as 1.įor example, linolenic acid, an omega 3-fatty acid, has 18 carbons and double bonds at positions 9,12, and 15, counting from the carboxyl end. The carboxyl referencing system counts the position of all the double bonds from the carboxyl carbon, which is numbered as 1. There are several common numbering methods. Those with double bonds are unsaturated fatty acids and those with only single bonds are saturated fatty acids because they are saturated with the largest number of hydrogen atoms possible.įatty acids often have common names but can be systematically named according to the number of carbon atoms and the number and position of the double bonds in the carbon chain. The carbon connected to the carboxyl group is called the alpha carbon, and the methyl group carbon is known as the omega carbon.įatty acids vary in length and the presence of double bonds in the hydrocarbon chain. Triglycerides and most phospholipids consist of glycerol and fatty acid chains.įatty acids have methyl groups at one end of the chain and carboxyl groups on the opposite end. Lipids are a group of hydrophobic molecules that include triglycerides, which are used to store energy, and phospholipids, which are the major structural components of cell membranes.

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