2. They are present in all living cell. Their vey name, derived from the Greek word proteios which means "holding first place" signifies the importance of these substance.
4. Water-insoluble, oily or greasy biochemical compounds that can be extracted from cells by nonpolar solvents such as ether, chloroform of benzene.
A lipid is any of various organic compounds that are insoluble in water. They include fats, waxes, oils, hormones, and certain components of membranes and function as energy-storage molecules and chemical messengers.
