Open Lipid

Lipids Chemistry

Definition: Biological molecules with a diverse range of structures including fats, waxes, steroids, and phospholipids.
Solubility: Soluble in organic solvents and nearly insoluble in water due to their hydrophobic nature, primarily attributed to hydrocarbon chains.
Components: Some lipids contain non-lipid groups such as phosphoryl, amino, or sulfate.

Energy Source: Lipids store significantly more energy per gram compared to carbohydrates and proteins.
Fat-Soluble Vitamins: Act as natural solvents for fat-soluble vitamins.
Protection: Provide cushioning for internal organs (e.g., kidneys) and thermoregulation (fat under the skin acts as an insulator).
Nervous System: Myelin sheath in nerve fibers acts as an electrical insulator.
Lipoproteins: Participate in the structure of the cell membrane and are essential for lipid transport in the bloodstream.
Biosynthesis: Acetyl CoA derived from fatty acid oxidation is crucial for synthesizing important compounds such as steroids.

Definition: Principal building blocks of complex lipids composed of a long hydrocarbon chain (tail) and a terminal carboxyl group (head).
Types:
- Saturated Fatty Acids: Contain no double bonds (e.g., Stearic acid). Formula: CH₃-(CH₂)n-COOH.
- Unsaturated Fatty Acids: Contain one or more double bonds (e.g., Oleic acid). Classified into mono-unsaturated (MUFA) and polyunsaturated (PUFA).
Amphipathic Nature: Possess both polar (hydrophilic) and nonpolar (hydrophobic) groups.
Classification by Chain Length:
- Short-chain: Less than 6 carbon atoms.
- Medium-chain: 6-12 carbon atoms.
- Long-chain: More than 12 carbon atoms.

Common Biological Fatty Acids:
- Lauric acid (12:0): Dodecanoic acid, melting point 44.2°C.
- Myristic acid (14:0): Tetradecanoic acid, melting point 53.9°C.
- Palmitic acid (16:0): Hexadecanoic acid, melting point 63.1°C.
- Stearic acid (18:0): Octadecanoic acid, melting point 69.6°C.
- Arachidic acid (20:0): Melting point 77°C.

Characteristics: Have one or more double bonds, typically in cis configuration.
Classification:
- Mono-unsaturated Fatty Acids (MUFA): One double bond.
- Polyunsaturated Fatty Acids (PUFA): More than one double bond.
- Nomenclature:
  - Delta system: Counts from the carboxylic end.
  - Omega system: Counts from the methyl end.

Definition: Polyunsaturated fatty acids that must be obtained from the diet (e.g., Linoleic acid, Arachidonic acid).
- Importance:
  - Essential for growth.
  - Important for phospholipid formation.
  - Arachidonic acid's role in biosynthesis of prostaglandins.
  - Protects against atherosclerosis by forming cholesterol esters.

Physical Properties:
- Solubility:
  - Short-chain fatty acids: Soluble in water.
  - Long-chain fatty acids: Soluble in non-polar solvents.
- Melting Point: Depends on chain length and presence of double bonds; shorter and unsaturated fatty acids tend to be liquid at room temperature, while longer and saturated fatty acids are solid.
Chemical Properties:
- Salt Formation: Fatty acids can form soaps when reacting with bases.
- Ester Formation: Fatty acids react with alcohols.
- Reduction and Oxidation: Can be reduced to aldehydes and alcohols or oxidized producing peroxides or other compounds.

Simple Lipids: Esters of fatty acids with glycerol (e.g., triaacylglycerol, waxes).
Compound Lipids: Includes phospholipids (e.g., phosphoglycerides).
Derived Lipids: Include steroids and isoprenoids.

Definition: Esters of fatty acids with glycerol.
Sources: Animal fats (butter) and plant oils (olive oil, corn oil).
Properties:
- Insoluble in water but soluble in non-polar solvents.
- Triglycerides may be simple (same fatty acids) or mixed (different fatty acids).

Definition: Complexes of lipids and proteins.
Types: Chylomicrons, VLDL, LDL, HDL, varying by lipid/protein composition and function.
Function: Aid in lipid transport and metabolism in the body.