1. Lipids Lipids are energy storage in cell membrane and regulators of cell metabolism. Lipids are hydrophobic biological compounds that are insoluble in water, but soluble in nonpolar solvent such as benze, chloroform and ether. They are present in the nonaqueous biological phase such as plasma membrane. Cells can alter the mix of lipids in their membrane to compensate for changes in temperature or to increase their tolerance to the presence of chemical agents such as ethanol.

2. Lipids Fatty Acids : The major component in most lipids is made of a straight chain of hydrophobic hydrocarbon group, with a carboxyl group (hydrophilic) at the end. A typical saturated fatty acid has the form of CH 3 -(CH 2 )n –COOH Where n is typically between 2 and 20, such as acetic acid CH 3 COOH. A typical unsaturated fatty acid contain double –C=C-, or triple bonds on the hydrocarbon chain, such as Oleic acids: CH 3 -(CH 2 ) 7 -HC=CH-(CH 2 ) 7 -COOH

3. Important Lipids - Fats Fats are lipids that are esters of fatty acids with glycerol. glycerolFatty acidsfat

4. Fats Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. They also serve as energy stores for the body and can serve as biological fuel-storage molecules. Fats are broken down in the body to release glycerol and free fatty acids. glycerol can be converted to glucose by the liver and thus used as a source of energy. The fatty acids are a good source of energy for many tissues, especially heart and skeletal muscle.

5. Lipids - Phospholipids Phospholipids such as glycerophospholipids are built on a glycerol core to which are linked two fatty acid-derived "tails" by ester linkages and one "head" group by a phosphate ester linkage. Phospholipids are key components to control the entry or exit of molecules in the cell membrane.

6. Lipids - Steroids A steroid is a lipid characterized by a carbon skeleton with four fused rings. Different steroids vary in the functional groups attached to these rings.

7. Steroids Their most important role in most living systems is as hormones (e.g. cortisol) to regulating the cell metabolism. In human physiology and medicine, the most important steroids are cholesterol functioning chiefly as a protective agent in the skin and nerve cells, a detoxifier in the bloodstream, and as a precursor of many steroids.

8. Summary of lipids Lipids are energy storage in cell membrane and regulators of cell metabolism. - fat, phospholipids and steroids. - Important components in cell membrane to compensate for changes in temperature or increase the cell tolerance for some chemicals.