6.3 Structure of Lipids

Chapter 6 ~ The Chemistry of Life

Section 6.3 p. 157 - 163

The Structure of Lipids

• Lipids are made of two subunits:– Glycerol– Fatty acids

General structure of fatty acids: a type of lipid

• Fatty acids are carboxylic acids with a long hydrocarbon tail. In the general structure, "R" represents the large hydrocarbon tail.

• R generally represents a hydrocarbon chain of 3 to 19 C atoms.

A fatty acid ~ myristic acid

• Fatty acids are carboxylic acids with a long hydrocarbon tail. In the general structure, "R" represents the large hydrocarbon tail. In this example, the hydrocarbon tail has 13 carbons.

• Myristic acid is in butterfat and coconut oil.

• It is a saturated fatty acid: the hydrocarbon tail has no double bonds.

A fatty acid ~ oleic acid

• In this example, the hydrocarbon tail has 17 carbons.

• Oleic acid is in olive oil, peanut oil, and human fat.

• It is an unsaturated fatty acid: the hydrocarbon tail has a double bond.

• Since there is only one double bond, the fatty acid is monounsaturated.

• Saturated fats have all single bonds.

• Unsaturated fats have at least one double bond.

Structure of glycerol, a compound that reacts with fatty acids

• The -OH groups on glycerol can react with the -COOH groups on fatty acids, causing the fatty acid to join to the glycerol, and releasing water.

• The glycerol and 3 fatty acids react to form triglycerides.

Glycerol and fatty acids form triglycerides

• The -OH groups on glycerol can react with the -COOH groups on fatty acids, causing the fatty acid to join to the glycerol, and releasing water.

• The glycerol and fatty acids react to form triglycerides.

General formulas show how glycerol and fatty acids form

triglycerides

• The -OH groups on glycerol can react with the -COOH groups on fatty acids, causing the fatty acid to join to the glycerol, and releasing water.

• The glycerol and fatty acids react to form triglycerides.

Structural formulas show how glycerol and stearic acid forms

tristearin, a triglyceride

• The -OH groups on glycerol can react with the -COOH groups on stearic acid, causing the stearic acid to join to the glycerol, and releasing water.

• The glycerol and stearic acid react to form tristearin, a triglyceride.