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2.2.f Describe the molecular structure of a triglyceride with reference to the formation of ester bonds and relate the structure of triglycerides to their functions in living organisms
IMPORTANT DEFINITIONS
- Fatty Acids: series of long hydrocarbon chains that contain –COOH group (carboxyl group).
- Ester Bond: a bond that is formed after a reaction takes place between an acid and an alcohol.
- Glycerol: alcohol containing three –OH groups (hydroxyl group).
- Unsaturated fatty acids: contain double carbon bonds (i.e., C=C bonds)
- Saturated fatty acids: contain single carbon bonds (i.e., C-C bonds)
WHAT ARE TRIGLYCERIDES AND LIPIDS?
- Lipids include fats and oils that are formed by combining fatty acids and alcohol.
- They contain C, H and O.
- Triglycerides are formed by joining three fatty acids and a glycerol molecule via condensation to form ester bonds.
- Triglycerides are insoluble in water
- However, they are soluble in certain organic solvents, including ether, chloroform and ethanol.
- Fatty acids with double bonds in the hydrocarbon chain are unsaturated; single bonds are saturated fatty acids.
This image shows the process of condensation to form a a triglyceride from glycerol and three fatty acid molecules.
ROLE OF TRIGLYCERIDES
- Triglycerides are good energy reserves (better than carbohydrates).
- Acts as an insulator
- Provides buoyancy
- When oxidised during respiration, gives carbon dioxide and water, and therefore is a metabolic source of water.
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References:
Jones, M., & Parkin, M. (2018). Cambridge International AS and A Level Biology. Cambridge: Cambridge University Press.