ANSC 221v - SAG 206

FATS

Fats are substances that are insoluble in organic solvents, like ether.

Fats are composed of the elements C, H, and O, just like carbohydrates, but unlike carbohydrates have very little Oxygen in relation to Carbon and Hydrogen.

There are several categories of lipids (fats), such as waxes, terpenes, sterols, and others, but the only category of great significance in nutrition (for us) is xxxx, composed of tri- (and di- and mono-) glycerides.

Triglycerides are composed of ONE molecule of glycerol and three fatty acids. (Diglycerides have two, and monoglycerides have one, fatty acid attached to glycerol).

Diagramatically, they appear like:

 H

OH-C-fatty acid--------------

 |

OH-C-fatty acid--------------

 |

OH-C-fatty acid---------------

 H

Fatty Acids

Fatty acids of importance to us in nutrition are:

• Volatile Fatty Acids - important in rumen fermentation:

• Acetic acid, with 2 carbon atoms - CH₃COOH
• Propionic acid, with 3 carbon atoms - CH₃CH₂COOH
• Butyric acid, with 4 carbon atoms - CH₃CH₂CH₂COOH
• Long Chain SATURATED Fatty Acids:
• Palmitic acid - with 16 carbon atoms - CH₃(CH₂)₁₄COOH
• Stearic acid - with 18 carbon atoms - CH₃(CH₂)₁₆COOH
• Long Chain UNSATURATED Fatty Acids that are not essential:
• Oleic acid - with 18 carbon atoms and 1 double bond
• Long Chain UNSATURATED Fatty Acids that are essential - ESSENTIAL FATTY ACIDS, EFA's:
• Linoleic acid - 18 carbon atoms, 2 double bonds
• Linolenic acid - 18 carbon atoms, 3 double bonds
• Arachidonic acid - 20 carbon atoms, 4 double bonds

Saturated vs. Unsaturated Fatty Acids

Saturated fats contain all the hydrogen that they can contain. Since every carbon atom must have 4 bonds, each "internal" carbon connects to 2 adjacent carbons and 2 hydrogen.

 H H H H H
HC-C-C-C-C--etc
 H H H H H

Unsaturated fats have "double bonds" between some carbons, and are missing some of the hydrogen they could contain.

 H H     H
HC-C-C=C-C--etc with double bonds between certain carbons
 H H H H H

Some of the polyunsaturated fatty acids (fatty acids with several double bonds) are essential in the diet because the bonds are located in spots where animals are not able to form them.