12B Fatty Acids

Fatty Acids: An Introduction to Cellular Membranes and Lipid Metabolism

General Characteristics of Fatty Acids

• Definition: Fatty acids are carboxylic acids with long hydrocarbon chains.

• Typical Length: Most fatty acids contain between 12 to 24 carbon atoms.

• Structure: Generally linear in eukaryotic cells.

• Double Bonds: Can possess one or more double bonds (0-6).

  • Cis Double Bonds: These create a 30° kink in the hydrocarbon chain.

Chemistry 101: Structural Representations of Fatty Acids

• Example of Fatty Acids:

  • Stearate (n-Octadecanoate): 18:0 (Stearic Acid)

  • Oleate (cis-9-Octadecanoate): 18:1 (D9) or 18:1c (D9)

Nomenclature

• Most fatty acids have an even number of carbon atoms.

• Naturally occurring unsaturated fatty acids typically contain cis double bonds.

Advanced Fatty Acid Nomenclature

• Specific Examples:

  • Stearate (n-Octadecanoate): 18:0

  • Linolenate (9,12,15-Octadecanoate): 18:3 (D9,12,15)

  • Notation: 18:3 n-3 indicates it is an ω3 fatty acid.

Properties of Fatty Acids Based on Hydrocarbon Chains

Melting Point Data

Influence of Structure on Properties

• The properties of fatty acids significantly influence the properties of larger molecules into which they are incorporated.

• Historical Note: Elaidate, the major trans fat in hydrogenated vegetable oils, is also found naturally in cow milk.

Fatty Acid Examples

Biological Lipids and Their Building Blocks

• Many biological lipids are derived from simple building blocks:

  • Glycerol

  • L-Serine

  • Choline

  • Ethanolamine

  • Inositol

• Additional options: L-serine and phosphate backbone with fatty acid tails and polar head groups can combine in various ways to form complex lipids.

Conclusion

• The study of fatty acids is crucial for understanding cellular membranes and lipid metabolism. Their structures, nomenclature, properties, and impact on biological systems are foundational concepts in biochemistry and cell biology.