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 

• 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)

• 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. 

• 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.