Lipids
Lipids
- Lipids are macromolecules that contain carbon, hydrogen and oxygen atoms. Unlike carbohydrates, lipids contain a lower proportion of oxygen
- Lipids are non-polar and hydrophobic (insoluble in water)
- Triglycerides are a kind of lipid that forms the main component of fats and oils
- Lipids play an important role in energy yield, energy storage, insulation and hormonal communication
Triglycerides
- Are non-polar, hydrophobic molecules
- The monomers are glycerol and fatty acids
- Glycerol is an alcohol (an organic molecule that contains a hydroxyl group bonded to a carbon atom)
- Fatty acids contain a methyl group at one end of a hydrocarbon chain known as the R group (chains of hydrogens bonded to carbon atoms, typically 4 to 24 carbons long) and at the other is a carboxyl group
- The shorthand chemical formula for a fatty acid is RCOOH
- Fatty acids can vary in two ways:
- Length of the hydrocarbon chain (R group)
- The fatty acid chain (R group) may be saturated (mainly in animal fat) or unsaturated (mainly vegetable oils, although there are exceptions e.g. coconut and palm oil)
- Saturated fatty acids contain no carbon-carbon double bonds
- The hydrocarbon chain is saturated with hydrogen atoms due to the absence of double bonds
- They form unbranched, linear chains
- Unsaturated fatty acids can be mono or poly-unsaturated
- If H atoms are on the same side of the double bond they are cis-fatty acids and are metabolised by enzymes
- If H atoms are on opposite sides of the double bond they are trans-fatty acids and cannot form enzyme-substrate complexes, therefore, are not metabolised. They are linked with coronary heart disease
Examples of different types of fatty acids with the functional groups and presence of double bonds highlighted
Function of lipids
- Triglycerides are fats and oils
- Fatty acid and glycerol molecules are the components that make up triglycerides
- Fats and oils have a number of important functions in organisms: energy storage, insulation, buoyancy, and protection