“Biological Molecules” is the 2nd Chapter in the new course of Biology for intermediate premedical students. In this chapter the students will learn the Introduction to biochemistry, chemical composition of cell, relationship between structure and function of molecules. Complex structural formulae and details are not required. Properties of biological importance, Synthesis of large molecules from small molecules by condensation and their break down by hydrolysis. Importance of tetravalent nature of carbon, ability of carbon to form different kind resulting in formation of complex shapes of organic molecules. Amino acids, and general structure of amino acid, chains of amino acids. Four levels of structure of protein molecule, significance of sequence of amino acids and shape of protein molecule, Functions of Proteins, Monosaccharides, oligosaccharides and polysaccharides, Functions of carbohydrates, Chemically diverse groups of hydrocarbons, Acylglycerols (fats & oils): energy storage, saturated and unsaturated fatty acids and their importance, Phospholipids: hydrophobic and hydrophilic portions, phosolipids in biological membranes, Terpenoids: steroids, carotenoids, terpenes and their important roles, Waxes: their protective role, Nucleic acids as polymers of nucleotides, Structure of a nucleotide. Mononucleotide: ATP as energy rich compound, Dinucleotide: NAD as coenzyme, Polynucleotides: Nucleic acids as informational macromolecules, Two main kinds of nucleic acids i.e., DNA and RNAs, DNA as hereditary material and significance of its nucleotides base sequence, RNA as carrier of information, Glycolipids, Glycoproteins, Lipoproteins and Nucleoproteins.