Lipids in living organisms:
Lipids make up about5% of the organic matter of a cell. At room temperature, a solid lipid is called a fat and a liquid lipid is called oil. Lipids perform a number of functions within living organisms:
· a source of energy- lipids can be respired to release energy to generate ATP
· Energy storage- lipids are stored in adipose cells (cells that store lipid) in ‘fat stores’ in organisms.
· all biological membranes are made from lipids
· insulation- e.g. the blubber in whales is lipid that reduces heat loss; lipids also provide ‘electrical insulation’ around long nerve cells
· protection- e.g. the surface (cuticle) of plant leaves is protected against drying out by a layer of lipid
· some hormones are lipids (steroid hormones)
Lipids contain the elements carbon, hydrogen and oxygen. The proportion of oxygen in lipids is very low, much lower than that found in carbohydrates. Lipids are insoluble in water.
Glycerol and fatty acids:
Glycerol and fatty acids are found in all the fats and oils that perform roles in energy storage and supply, and those found in membranes. While the glycerol molecule is always the same, the fatty acid molecule found in lipids can differ significantly. As with amino acids, animals cannot make some of the fatty acids they need from the raw materials taken into their bodies. These are called essential fatty acids, and they must be taken in ‘complete’ as part of the diet.
Fatty acids – similar but very different:
All fatty acids have…