Structure of Fats
Let's start by reviewing the structure of fats from an earlier lesson. Fats are triesters of glycerol and long-chained carboxylic acids.
They are formed (as shown below and in Example 5 in your workbook) by dehydration reactions in which the three OH groups of a glycerol molecule react with the carboxylic acid groups of three different fatty acids to form three ester bonds and also three molecules of water. The resulting molecule is called a triglyceride because of the three ester groups that are formed with glycerin. (Note: The bonds coming down from the carbon atoms on the right sight of this diagam are supposed to line up with the single-bonded oxygen atoms below them.)
Just as the fats can be assembled (or synthesized) by means of a dehydration reaction, they can also be dissembled by hydrolysis reactions to reform the glycerol and fatty acids which were present when it was put together. In our bodies, this reaction is generally carried out in the presence of enzymes that catalyze the hydrolysis reaction.
This reaction can take place outside our bodies in the presence of a strong base such as sodium hydroxide. Under those conditions, the reaction is called a saponification reaction and the products are glycerol and also salts of long-chained fatty acids which are also known as soap. (A similar diagram is shown in Example 6 in your workbook.)
Monoglycerides and Diglycerides
If only one long-chained carboxylic acid is bonded, it is called a monoglyceride. If only two are bonded, it is called a diglyceride. Only with three is it called a triglyceride.
E-mail instructor: Sue Eggling
Clackamas Community College