Lipids Classification and Saponification Quiz

Classification Based on Saponification

• Lipids are classified into saponifiable (can undergo saponification) and nonsaponifiable (cannot) categories.
• Saponifiable lipids include acyl glycerol, waxes, sphingolipids, and phospholipids.
• Nonsaponifiable lipids include steroids and prostaglandins.
• Saponification involves alkalis, typically potassium hydroxide (KOH) or sodium hydroxide (NaOH), to break esters into carboxylic acid salts and alcohols.

Classification Based on Chemical Composition

• Simple Lipids: Esters of fatty acids with various alcohols.

  • Fats and Oils (Triacylglycerols): Composed of fatty acids and glycerol; fats are solid, oils are liquid at room temperature.
  • Waxes: Esters of fatty acids with high molecular weight alcohols (e.g., cetyl alcohol).

• Complex Lipids (Compound Lipids): Contain other organic molecules besides fatty acids and glycerol.

  • Phospholipids: Include a phosphoric acid residue and potentially nitrogenous bases.
    • Classes: Glycerophospholipids (e.g., lecithin, cephalin) and sphingophospholipids (e.g., sphingomyelin).
  • Glycolipids: Composed of fatty acids, sphingosine, and carbohydrates (e.g., cerebrosides, gangliosides).
  • Lipoproteins: Macromolecular lipid-protein complexes classified by density (HDL, IDL, LDL, VLDL).
  • Other Complex Lipids: Include sulfolipids, amino lipids, and lipopolysaccharides.

• Derived Lipids: Hydrolysis products of simple and complex lipids, including fatty acids, glycerol, mono and diacylglycerols, and lipid-soluble vitamins.

• Miscellaneous Lipids: Include compounds with lipid-like characteristics, such as carotenoids and terpenes.

• Neutral Lipids: Uncharged lipids like acylglycerols, cholesterol, and cholesteryl esters.

Fatty Acid Classification

• Fatty acids are carboxylic acids with hydrocarbon chains, featuring a polar head and nonpolar tail (amphipathic).
• Typically consist of even numbers of carbons; common ones include palmitic (16C) and stearic acid (18C).

Saturated Fatty Acids

• Fully saturated fatty acids exhibit an extended conformation, minimizing steric hindrance and allowing stable crystalline structure.

Unsaturated Fatty Acids

• Monounsaturated Fatty Acids (MUFA): One double bond (e.g., olive oil).
• Polyunsaturated Fatty Acids (PUFA): More than one double bond (e.g., canola oil).
• Naturally occurring unsaturated fats are typically liquid at room temperature; plant-derived oils are rich in cis fatty acids.
• Cis fats keep fatty acids liquid; trans fats, created through hydrogenation, are associated with health risks.

Roles of Fats

• Essential for proper bodily function and absorption of fat-soluble vitamins.
• Serve as efficient energy storage and provide body insulation.

Essential vs. Non-Essential Fatty Acids

• Essential Fatty Acids (EFA): Must be obtained through the diet (e.g., linoleic acid, linolenic acid, arachidonic acid).
• Non-Essential Fatty Acids: Synthesized by the body (e.g., palmitic acid, oleic acid).

Functions of Essential Fatty Acids

• Contribute to membrane structure, cholesterol transport, and eicosanoid synthesis.
• Play critical roles in cardiac cell function, immune response, and blood pressure regulation.
• Sources of EFAs include fish, flaxseed oil, and leafy vegetables.

Deficiency in Essential Fatty Acids

• Can lead to phrynoderma, characterized by skin lesions and hair loss.
• In infants, deficiency may cause eczema.

Classification Based on Lipid Function

• Storage Lipids: Primarily triglycerides, stored in adipocytes and seeds for energy and insulation.
• Triacylglycerols: Key storage form of fatty acids; chemically nonpolar and insoluble in water.