Understanding Chemistry of Fatty Acids #biochemistry #fattyacids #ipumusings
Understanding Chemistry of Fatty Acids
Author: Tanuj Handa
What are fatty acids?
Fatty acids are carboxylic acids with hydrocarbon chains (–CH₂–CH₂–CH₂–) and represented by a chemical formula R-COOH, where R stands for hydrocarbon chain. A fatty acid is a long-chain aliphatic carboxylic acid.
Important points about Fatty Acids:
➀ They are monocarboxylic acids.
➁ Number of carbon atoms is even, though an odd number of fatty acids exist but are very rare.
➂ They may be saturated or may be unsaturated
➃ A fatty acid molecule contains both polar (hydrophilic) and non-polar (hydrophobic) regions; such molecules are called amphipathic molecules.
➄ Fatty acids, which are not synthesized in the body, and hence have to be supplied in the diet are called essential fatty acids. e.g. Linoleic acid, a-Linolenic acid and Arachidonic acid.
➅ Mammals and plants contain both monosaturated and polyunsaturated fatty acids whereas all the fatty acids containing double bonds that are present in bacteria are monounsaturated.
➆ The most common saturated fatty acids are palmitic acid (C₁₆), stearic acid (C₁₈) and among the unsaturated fatty acid, oleic acid (C₁₈).
➇ Fats/oils are a tremendous source of energy and 40% of total calories are provided by fatty acids that come from triglycerides and phospholipids.
Main Functions of Fatty Acids:
1. They are the building blocks of more sophisticated membrane lipids. Building blocks of phospholipids and
glycolipids.
2. Main components of fat that have been accumulated in the body (triacylglycerols).
3. Fatty acid derivatives act as hormones (such as prostaglandins) and intracellular messengers.
4. Fatty acids covalently modify a large number of proteins. E.g. palmitic and myristic acids
Classification of Fatty Acids
See the figure below:
Straight Chain Fatty Acids: Carbon atoms arranged linearly. Classified as:
i. Saturated fatty acids
ii. Unsaturated fatty acids
Saturated Fatty Acids: No double bonds. Can be even carbons acids (stearic acid) or odd carbons acids ( e.g. propionic acid.)
Unsaturated Fatty Acids: Contain double bonds in their hydrocarbon chain. Further classified as monoenoic acids or polyeonic acids. Monoenoic or monounsaturated fatty acids have a single double bond. Polyenoic or polyunsaturated fatty acids contain two or more double bonds.
Branched Chain Fatty Acids: Examples are Isovaleric acid and Isobutyric acid.
Substituted Fatty Acids: One or more H-atoms are replaced by other groups e.g. Ricinoleic acid of castor oil.
Cyclic Fatty Acids: Present in certain bacteria e.g. hydnocarpic acid
What are Essential Fatty acids?
Fatty acids, which are not synthesized in the body, and hence have to be supplied in the diet are called essential fatty acids. Essential fatty acids serve as precursors of Eicosanoids (local hormones). They help in lipid transport. They help in lowering serum cholesterol (anti-atherogenic effect). They help in promoting fat mobilization from the liver (Lipotropic effect).
The deficiency of essential fatty acids in the diet often leads to skin effects e.g. dry skin or toad skin.
Examples of essential fatty acids are Linoleic acid, a-Linolenic acid and Arachidonic acid.
Naturally occurring fatty acids
Saturated: Lauric acid, Myristic acid, Palmitic acid, Stearic acid
Unsaturated: Oleic acid, Linoleic acid, Linolenic acid
Fatty Acids found in Mammalian Tissues
Acetic acid, Lauric acid, Myristic acid, Palmitic acid, Stearic acid
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