Biochemistry is a fundamental science that studies the chemical processes and molecular interactions occurring within living organisms. It helps explain how cells, tissues, and organs function at the molecular level. Major Biomolecules Biochemistry focuses on four major classes of biological molecules: Carbohydrates: Important sources of energy and structural components of cells. Lipids: Essential for energy storage, cell membrane structure, and the synthesis of certain hormones. Proteins: Perform numerous biological functions, including enzymatic catalysis, transport, defense, and cellular structure. Nucleic Acids (DNA and RNA): Store and transmit genetic information and regulate protein synthesis. Enzymes and Energy Enzymes are biological catalysts that accelerate biochemical reactions without being consumed during the reaction. Biochemistry also examines how cells produce and utilize energy. One of the most important cellular energy molecules is ATP (Adenosine Triphosphate), which serves as a major energy carrier in biological systems. Importance of Biochemistry in Medicine Biochemistry is essential for understanding disease mechanisms and interpreting laboratory investigations, including measurements of glucose, creatinine, liver enzymes, lipids, and hormones. It also contributes to biomarker discovery, drug development, and the understanding of molecular changes associated with disease. Conclusion Understanding the fundamentals of biochemistry provides a scientific basis for explaining how cells function, how nutrients are converted into energy, and how diseases develop at the molecular level. Therefore, biochemistry represents an essential link between life sciences, medicine, and laboratory diagnostics. Al-Mustaqbal University – Ranked First Among Iraqi Private Universities