Triglycerides, also known as triacylglycerols, are the most abundant form of stored fat in the human body. In the book "Advanced Nutrition and Human Metabolism," authors Sareen Gropper, Jack Smith and James Groff state that triglycerides account for 95 percent of dietary fat. During digestion, dietary fat is converted to triglycerides. Excess triglycerides are stored in fat cells for the body to use as an energy source between meals. However, excess triglycerides from a diet high in fat and processed foods can lead to coronary heart disease. Less common causes other than dietary intake, such as diabetes, can cause elevated levels of triglycerides.
General Chemical Structure
Triglycerides have a simple chemical structure that consists of one glycerol molecule and three fatty acids. The nature of the triglyceride molecule changes with the combination of fatty acids attached to the glycerol. The fatty acids can be all saturated, all polyunsaturated, all monounsaturated or any combination.
Glycerol
Glycerol, as described in "Advanced Nutrition and Human Metabolism," is a three-carbon alcohol that is the backbone of triglyceride. An alcohol molecule is an oxygen-hydrogen molecule attached to a carbon atom. Each carbon in glycerol is bonded to an alcohol molecule. A dehydration process takes place when a fatty acid attaches to glycerol. The hydrogen of the alcohol molecule on glycerol is liberated along with two oxygen atoms released from the fatty acid to form water. A bond, called an ester bond, between the fatty acid and glycerol is formed as a result of this process. This type of bonding occurs on all three of the glycerol alcohols to form the triglyceride molecule.
Fatty Acids
Fatty acids are the simplest form of fat. They can be saturated, monounsaturated, or polyunsaturated. The American Heart Association describes saturated fatty acids as those with every carbon atom bonded to a hydrogen atom. A monounsaturated fatty acid is described as a fat molecule with one carbon double bonded to another carbon, while all other carbon atoms are attached to hydrogen with a single bond. The double bond is formed when a hydrogen atom is eliminated. The missing hydrogen leaves an extra electron in the carbon to bond with another carbon. Polyunsaturated fatty acids are described as having more than one double bond, meaning more hydrogen atoms have been eliminated.
Forms of Triglycerides
A triglyceride's physical form at room temperature varies depending on the combination of fatty acids attached to the glycerol. Triglycerides exist as solids like butter, or as liquids like olive oil. If a triglyceride is made primarily of unsaturated fatty acids, it will be oil at room temperature. The number of double bonds in the fatty acid determines the melting point. More double bonds equals a lower melting point. For example, saturated fatty acids have no double bonds, a higher melting point and exist as solids at room temperature.
References
- "Advanced Nutrition and Human Metabolism, Fifth Edition"; Sareen Gropper et al; 2009
- The American Heart Association; Triglycerides; May 6, 2011
- The American Heart Association; Saturated Fats; October 29, 2010
- The American Heart Association; Monounsaturated Fats; October 29, 2010
- The American Heart Association; Polyunsaturated Fats; October 29, 2011
