Lipids - presentation from class

LIPIDS

  • Lipids are an important group of molecules.

  • Examples include cholesterol, olive oil, and butter.

  • They have various functions in biological systems.

Properties of Lipids

  • Insoluble in water (hydrophobic): Lipids are non-polar and cannot dissolve in water.

  • Soluble in organic solvents: They can dissolve in solvents like ethanol and propanone.

Types of Lipids

Fats and Oils

  • Difference: Fats are typically solid at 20⁰C, while oils are liquid at this temperature.

  • Composition: All fats and oils are made from carbon (C), hydrogen (H), and oxygen (O) atoms.

  • Comparison with carbohydrates: Fats and oils contain less oxygen than carbohydrates.

  • Building Blocks: Made from glycerol and fatty acids.

Glycerol

  • Chemical Structure: Also known as propane 1,2,3-triol (C3H8O3).


Fatty Acids

  • Over 70 types of fatty acids are found in living organisms.

  • They have long hydrocarbon chains with a terminal carboxyl group (-COOH).

  • Variability:

    • (a) Length of hydrocarbon chain (typically 15-17 carbons long).

    • (b) Saturation levels (saturated vs. unsaturated).

Saturated Fatty Acids

  • Chemical Structure: Contains only single carbon-carbon bonds.

  • Example: Lauric acid found in coconut oil.

  • Structure summary:

    • No carbon-to-carbon double bonds.

    • Full quota of hydrogen atoms.

    • Common in animal fats (e.g., butter, meat).

Unsaturated Fatty Acids

  • Types:

    • Monounsaturated: Contains one carbon-carbon double bond.

    • Polyunsaturated: Contains multiple carbon-carbon double bonds.

  • Example: Olive oil (monounsaturated) and fish oils (polyunsaturated).

  • Structure Summary:

    • Does not contain full quota of hydrogen atoms.

Esterification Reaction

  • Glycerol + fatty acids undergo a condensation reaction known as esterification, forming ester bonds.

  • Types of products from this reaction:

    • Monoglyceride: Glycerol + 1 fatty acid.

    • Diglyceride: Glycerol + 2 fatty acids.

    • Triglyceride: Glycerol + 3 fatty acids.

Triglycerides

  • Formation: Glycerol reacts with three fatty acids to form triglyceride.

  • Diagram of formation:


  • Hydrolysis: Triglycerides can be broken down into fatty acids and glycerol through hydrolysis (water is added).

Hydrolysis of Diglycerides

  • When diglycerides hydrolyze, they produce monoglycerides and fatty acids.

Additional Notes

  • Hydrocarbon chains of fatty acids can be simplified to a format denoted by (R) for clarity in diagrams.

Exam Preparation Tips

  • Understand the structure and properties of triglycerides, monoglycerides, and diglycerides.

  • Be able to identify saturation in fatty acids and their significance in biological processes.

  • Familiarize yourself with ester bond formation and hydrolysis reactions, as they are important in metabolism.