Polysaccharides are neutral polymeric compounds in which monosaccharide units are joined by glycosidic linkages. Proteins are long polymers of amino acids linked by peptide bonds. Nucleic acids are regarded as polynucleotides. These are the polymer of nucleotides. Lipids are oily, fatty or waxy substances present in living organisms. Chemically, lipids are esters of long chain fatty acids and alcohols.