These polymers contain linear segments and branched portions. They are storage compounds. In mammals the glycogen is mainly stored in the liver, with some in the muscles. Amino acids contain both an amine and a carboxylic acid group. They exist in an internally ionized form called a zwitterion.
Amino acids can react to form amide bonds-the basic linkage in protein structure.
Fatty Acids are nearly hydrocarbons. They are amphipathic molecules with a large non-polar hydrocarbon tail and a polar, water soluble carboxylate group. The hydrocarbon tails are not very reactive. These are a good energy source and storage form. Phospho-lipids are essential in cell membranes.