Fatty Acids: Types, Sources, and Functions

Common Fatty Acids
General Overview

  • Fatty acids are categorized based on their saturation level (saturated or unsaturated).

  • Saturated fatty acids have no double bonds between carbon atoms, while unsaturated fatty acids contain one or more double bonds.

Saturated Fatty Acids

  • General Structure: CH₃(CH₂)ₙCOOH where n represents the number of CH₂ groups.

  • Common Fatty Acids: graph

Unsaturated Fatty Acids

  • General Structure: For fatty acids with double bonds, numbering starts from the methyl (ω) end.

  • Common Unsaturated Fatty Acids:

    • Palmitoleic Acid (C16:1n-7):

    • Systematic Name: 9-Hexadecenoic acid

    • Oleic Acid (C18:1n-9):

    • Systematic Name: 9-Octadecenoic acid

    • Linoleic Acid (C18:2n-6):

    • Systematic Name: 9,12-Octadecadienoic acid

    • α-Linolenic Acid (C18:3n-3):

    • Systematic Name: 9,12,15-Octadecatrienoic acid

    • γ-Linolenic Acid (C18:3n-6):

    • Systematic Name: 6,9,12-Octadecatrienoic acid

    • Arachidonic Acid (C20:4n-6):

    • Systematic Name: 5,8,11,14-Eicosatetraenoic acid

    • Eicosapentaenoic Acid (C20:5n-3):

    • Systematic Name: 5,8,11,14,17-Eicosapentaenoic acid

    • Docosahexaenoic Acid (C22:6n-3):

    • Systematic Name: 4,7,10,13,16,19-Docosahexaenoic acid

Dietary Sources of Fatty Acids

  • Lauric (C12): Coconut (74%)

  • Myristic (C14): Beef (24-32%), Milk (25%)

  • Palmitic (C16): Palm (39%), Olive (9%)

  • Stearic (C18): Beef (37-43%), Milk (3%), Coconut (7%)

  • Oleic (C18:1): Olive (84%), Corn (34-62%)

  • Linoleic (C18:2): Soybean (52%), Safflower (78%)

Importance of Essential Fatty Acids

  • Some PUFAs (Polyunsaturated Fatty Acids) must be obtained through diet as humans cannot synthesize them beyond certain carbon locations.

  • Essential Fatty Acids:

    • Linoleic Acid (C18:2) – ω6 fatty acid (source of arachidonic acid)

    • Linolenic Acid (C18:3) – ω3 fatty acid (source of eicosapentaenoic acid)

  • These fatty acids play crucial roles in biological processes, including the formation of eicosanoids.

Eicosanoid Synthesis

  • Eicosanoids are derived from C20 fatty acids, including:

    • Arachidonic Acid (C20:4)

    • Eicosapentaenoic Acid (C20:5)

  • Synthesis pathways include:

    • Cyclooxygenase (COX) pathway: Produces prostaglandins and thromboxanes (important for inflammation).

    • Lipoxygenase (LOX) pathway: Produces leukotrienes (important for immune response).

Triacylglycerols (Triglycerides)

  • Comprised of glycerol and 3 fatty acids (FA), important energy storage molecules in adipose tissue.

  • Yield approximately 38kJ38 kJ of energy per gram, which is twice that of carbohydrates or proteins.

  • Advantages of triacylglycerols:

    • Insulation.

    • Non-solvated (do not require water for storage).

Phospholipids (GPLs)

  • Simplest glycerophospholipid: Phosphatidate (glycerol 3-phosphate with 2 FAs and a phosphate group).

  • Common types of GPLs include:

    • Phosphatidylcholine (Lecithin)

    • Phosphatidylserine

    • Phosphatidylethanolamine

    • Phosphatidylinositol

Breakdown of GPLs

  • Enzymes called phospholipases break down GPLs:

    • Phospholipase A1, A2, C, D.

  • Phospholipase A2 is notably found in snake venom, causing hemolysis.

Conclusion

  • Fatty acids play significant roles in health, energy storage, and cellular structures. Understanding their structures, sources, and functions is critical for dietary and health considerations.