Biochemistry Unit Macromolecules:Lipids
Lipids • Lipids are macromolecules that provide long term energy storage, insulation, cushioning of internal organs and are the main component of the cell membrane. • Lipids are the main structure of hormones. • All lipids are hydrophobic, which means they do not dissolve in water (hydro = water, phobic = fear). • Four main types of lipids which include: fats, phospholipids, steroids and waxes.
Fats • Most common energy storing molecule in an organism. One gram of fat contains two times as much energy as one gram of carbohydrate. • Most of the excess glucose that is not converted into glycogen is transformed into fat.
Fats • Glycerol is a three carbon atom that has three hydroxyl groups attached to the central carbon atoms. • Fatty acids consist of a long chain of carbon and hydrogen atoms with a terminal carboxyl functional group. These chains can be saturated, unsaturated or polyunsaturated. • Saturated fatty acid chains contain the maximum number of hydrogen atoms per carbon atom. These fats are generally found in animals and are solid at room temperature. • Unsaturated fats contain a carbon double bond and are found in plants. These fats are generally liquid at room temperature. • Polyunsaturated fats contain more than one carbon double bond and are found in plants and are liquid at room temperature.
Fats • The most common fat is the triglycerols/triglycerides which contain three fatty acid chains attached to a glycerol backbone.
Phospholipids • The main component of cell membrane. • Composed of two main parts; a phosphate head and two fatty acid tails. • Amphiphillic: The phosphate head is polar and hydrophilic while the fatty acid chains are non polar and hydrophobic. • Ester and Phosphate ester linkages
Steroids • Steroids are an important group of lipids that consist of four linked carbon rings. • Steroids are hydrophobicand include cholesterol and cortisol as well as hormones such as estrogen and testosterone.
Cholesterol • Found in the cell membranes and transported in the blood plasma of all animals. • Essential structural component of mammalian cell membranes • Required to establish proper membrane permeability and fluidity. • Manufacture of bile acids, steroid hormones, and several fat-soluble vitamins.
Waxes • Waxes are composed of long chains of fatty acids that are attached to an alcohol or a carbon ring. • Waxes are hydrophobic and are firm yet pliable. • Functions: cutin, bird feathers, beeswax