Triglycerides

• Most common lipids in living organisms; smaller than carbohydrates, but tend to join together creating globules, naturally occurring ones are esters formed by condensation reactions between glycerol (alcohol) and three organic/fatty acids
• Glycerol: soluble (alone) due to its three -OH groups and the molecular formula is C_3H_8O_3
• Glycerol Structural Formula

  
• Three organic/fatty acids are long, non-polar hydrocarbon chains with a polar carboxyl (-COOH) group at one end (gives it acidic properties), different fatty acids vary in length in but larger than glycerol, can be divided into: Saturated (only single bonds) and Unsaturated (one or more double,C=C, bonds)
• Formation - Glycerol + Fatty acids (e.g. stearic acid) → Ester + 3 water

  
• The Ester bond are formed as the polar parts of the glycerol molecule are lost linking it to the fatty acids, different triglycerides are produced dependant onn which three fatty acids
• The three fatty acids could be the same or different, the type fatty acids will affect their chemical and physical properties
• Compact and insoluble, sorted at high concentrations in cells as small droplets in the cytoplasm, it is a respiratory substance (releases twice as much energy as carbohydrates)
• It is hydrolysed (broken down) and oxidised to release energy for cell metabolism, lots of water is also released (metabolic water); important to certain animals - camels (can not drink for 3 weeks due to this store) or insects (never drink, only get it metabolically)
• If all (or most) of the fatty acids are unsaturated then an oil is formed, liquid at room temperature and a major energy store in seeds and fruits
• If all (or most) of the fatty acids are saturated then a saturated fat is formed, solid at room temperature and a major energy store in animals (stored as adipose)
• Adipose is useful for thermal insulation (in mammals), protection (for delicate organs), electrical insulations (myelin sheath, preventsion leakage), and buoyancy (lipidsfloat)
• Triglycerides are also converted to a variety of other molecules such as: Phospholipids, Cholesterol, Steroid Hormones