Contents: Preface. 1. Nucleic Acids. 2. Amino Acids, Peptides and Proteins. 3. Enzymes. 4. Lipids. 5. Concept of Energy in Biosystems. 6. Pharmaceutical Compounds: Structure and Importance. This book is based on the Choice Based Credit System (CBCS) syllabus of undergraduate courses in various universities in India. It covers the complete syllabus and discusses each topic in a lucid and accessible manner. This book is also useful for IIT JAM, IIT JEE, NEET, GATE, M.Sc., CSIR, UPSC and state exams to understand the basics of the current topics. Practice problems have been given for self-assessment at the end of each chapter to understand each topic clearly. This book also covers all the questions important from the examination point of view. Data and facts have been compiled in tabular form wherever required. This book is well-illustrated with figures.