Structure of Fatty acids and Derivatives : Simplified

Structure

1. Saturated fatty acid: Single bond (“S” for saturated and single bond)
2. Unsaturated fatty acid: Double bond(s), i.e. “D” for Double bonds, Decreased melting temperature and Decreased atherosclerotic risk (by decreasing LDL)
3. Trans-fatty acid: Unsaturated fatty acid which act like saturated fatty acid (hydrogenation of unsaturated fatty acid)

Nomencleture:

C 16:0 = Palmitic acid (16 C with 0 double bonds)

C 18:2 (9,12) = Linoleic acid (18 C with 2 double bonds at 9th and 12th C position)

Omega “x” = Total number of carbon atoms – Farthest double bond from the carboxylic acid side.

C 18:2 (9,12) = Omega 6 (18-12 = 6)

Saturated fatty acids (-ic)

Number of carbon atom increases by 2 in the order of albhabets – LMnoPqrS

L is the 12th letter, hence, has 12 carbon atoms.

1. Lauric acid: 12 C
2. Myristic acid: 14 C
3. Palmitic acid: 16 C
4. Stearic acid: 18 C

Unsaturated fatty acids (-eic or -nic)

A. Monounsaturated fatty acid (MUFA):

1. C 16:1 (9) = Palmitoleic acid (omega 7)
2. C 18:1 (9) = Oleic acid (omega 9)

B. Polyunsaturated fatty acid (PUFA):

Humans lack the ability to introduce double bonds in fatty acids beyond carbons 9 and 10, as counted from the carboxylic acid side. Hence, they become essential fatty acids:

1. Linoleic acid: C 18:2 (9,12) = omega 6 (precurosor of arachidonic acid)
   • Maximum in safflower oil
2. Alpha – Linolenic acid: C 18:3 (9,12,15) = omega 3 (reduce risk of cardiovascular disease)
   • Found in cold water fish, nuts
3. Gamma – Linolenic acid: C 18:3 (6, 9, 12) = omega 6

Phospholipids and Glycolipids

• Glycero-phospho-lipids = Glycerol + Phosphate + Fatty acid
  • Phosphatidylcholine (Lecithin): cell membrane
  • Dipalmitoyl lecithin: surfactant
  • Phosphatidyl insoitol: second messengers
  • Diphosphatidyl glycerol (Cardiolipin): inner mitochondrial membrane (maintain ETC and antigenic – cross react with antibodies against treponema pallidum)
• Shingo-phospho-lipids = Ceramide (Sphingosine + Fatty acid) + Phosphate, e.g. Sphingomyelin (myelin in nervous tissue)
• Glyco-sphingo-lipids = Ceramide (Sphingosine + Fatty acid) + Carbohydrate, e.g. Cerebrosides, Globosides, Gangliosides
  • Neutral:
    • Cerebroside (Ceramide + Monosaccharide): In brain and peripheral nerve (Galactocerebroside, Glucocerebroside)
    • Globoside (Glucocerebroside + Additional monosaccharide)
  • Acidic (negatively charged):
    • Gangliosides (Globoside + NANA i.e. N-acetyl neuraminic acid) = Ganglioside (ganglionic cells of CNS, particulary at nerve endings)
    • Sulfatides (Galactocerebroside + Sulfate) = Nerve tissue (myelin) and kidney
• Galacto-lipids = Glycerol + Galactose + Fatty acid

Ceramide is synthesized from Serine amino acid in endoplasmic reticulum.