What you will learn: • Elemental composition and chemical structure of lipids • Classification of fatty acids
• Distribution of saturated, monounsaturated and polyunsaturated fatty acids in food
• Essential fatty acids (EFAs), omega-3 fatty acids and cis and trans fatty acids • Classification of lipids by source
• Properties, biological functions, Recommended Daily Allowance (RDA)/ Reference Intake (RI) and energy value of lipids
• Associated dietary disorders • Digestion, absorption and utilisation of lipids
Lipids are one of the macronutrients. Lipids provide a concentrated source of energy. The term ‘lipid’ refers to both fats (solid at room temperature) and oils (liquid at room temperature).
Elemental composition of lipids Lipids are made up of three elements: carbon (C), hydrogen (H) and oxygen (O).
? List the three elements found in lipids (fats). (3) OL Chemical structure of lipids
Lipids are composed of triglycerides. A triglyceride contains one glycerol molecule and three fatty acid molecules.
Glycerol molecule: glycerol is a trihydric alcohol. It contains three hydroxyl (OH) groups.
Fatty acid molecule: a fatty acid is an organic compound. It is represented by the formula R-COOH (the R represents the hydrocarbon chain).
Triglyceride formation: each hydroxyl (OH) group of the glycerol molecule combines with hydrogens (H) from three fatty acids, resulting in the loss of three water molecules. This is known as a condensation reaction.
Triglyceride formation Leaving Certificate Home Economics 25
Glycerol molecule
A lipid hydrocarbon chain is a chain of carbon atoms that can vary in length from four to 24 atoms. The R signifies that the amount of carbons present is variable.
