lecture recording on 13 February 2025 at 17.03.07 PM

Fatty Acids

• Nomenclature: Understanding the naming conventions for fatty acids is crucial. They are identified by the number of carbon atoms and the presence of double bonds.

• Saturated vs. Unsaturated Fatty Acids:

  • Saturated Fatty Acids: No double bonds between carbon atoms. All carbon atoms are saturated with hydrogen.

  • Unsaturated Fatty Acids: Contain one or more double bonds, which introduces kinks in the fatty acid chain affecting its physical properties.

• Consequences of Double Bonds: Double bonds result in lower melting points and increased fluidity at room temperature compared to saturated fatty acids.

Lipids

• Definition and Functions: Lipids are diverse molecules that include fatty acids and serve various biological functions, including energy storage and cell membrane structure.

• Triacylglycerols (Triglycerides):

  • Structure: Composed of one glycerol molecule esterified to three fatty acids.

  • Esterification Process: Involves the formation of ester bonds, resulting in the release of water. Each triglyceride can have the same or different fatty acids.

  • Nonpolarity: Triglycerides are largely hydrophobic due to their long hydrocarbon chains.

• Hydrolysis Reaction: The breakdown of triglycerides, either enzymatically via lipases or using strong bases in laboratory settings, results in the regeneration of glycerol and release of free fatty acids.

Phospholipids

• Classes of Phospholipids: Contain a glycerol backbone esterified with two fatty acids and a phosphate group.

• Amphipathic Nature: Possess both hydrophilic (polar head) and hydrophobic (fatty acid tails) properties. Essential for forming cell membranes.

• Glycerophospholipids: Simplest form is phosphatidic acid, which can build more complex phospholipids like phosphatidylcholine (PC) and phosphatidylinositol (PI).

• Functions: Primarily structural components of cell membranes, not involved in energy storage like triglycerides.

Sphingolipids

• Backbone: Composed of sphingosine rather than glycerol.

• Ceramide Formation: Simple sphingolipid structure made by attaching one fatty acid to sphingosine via an amide bond.

• Sphingomyelins: A type of sphingolipid that includes a phosphate and can contain different head groups (like choline or ethanolamine).

Glycolipids and Gangliosides

• Cerebrosides: Sphingolipids with a monosaccharide attached instead of a phosphate.

• Gangliosides: Comprised of sphingolipids with polysaccharides, involved in important biological functions such as blood type determination.

Lipid Soluble Vitamins and Terpenes

• Fat Soluble Vitamins: Include vitamins A, D, E, and K. Essential for various bodily functions.

• Vitamin Functions:

  • Vitamin A (Retinol): Important for vision (phototransduction).

  • Vitamin E: Antioxidant properties.

  • Vitamin K: Essential for blood clotting.

• Terpenes and Isoprene Units: Building blocks for steroids and fat-soluble vitamins.

Membrane Structure and Lipid Bilayers

• Fluid Mosaic Model: Cells have lipid bilayers composed of various lipids, cholesterol, and proteins that confer fluidity and flexibility.

• Cholesterol's Role: Stabilizes membrane structure, preventing it from becoming too rigid or too fluid by interfacing between saturated and unsaturated fats.

• Proteins in Membranes:

  • Integral Membrane Proteins: Span the entire lipid bilayer (transmembrane proteins) with amphipathic characteristics, facilitating various functions including signal transduction.

  • Lipid Linked Proteins: Proteins attached to the membrane via lipid anchors.

Functional Importance of Lipid Structure and Composition

• Fluidity and Transition Temperature: The melting behavior of a membrane influences its function; at high temperatures, a membrane might become too fluid, while at low temperatures, it might become too rigid.

• Diversity in Fatty Acid Composition: Different fatty acids can impart unique properties to membranes, which can vary between tissue types and have significant biological importance.