Biochemistry Unit

 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.

 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.

 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.

 The most common fat is the triglycerols/triglycerides which contain three fatty acid chains attached to a glycerol backbone.

 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 are an important group of lipids that consist of four linked carbon rings.  Steroids are hydrophobic and include cholesterol and cortisol as well as hormones such as estrogen and testosterone.

 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 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