Cells are composed of organic molecules essential for life, including carbohydrates, lipids, proteins, nucleic acids, and ATP. These biomolecules provide energy, structural support, and biochemical functions necessary for cellular processes. Carbohydrates serve as a primary energy source, lipids store energy and form membranes, proteins perform various structural and enzymatic roles, and nucleic acids (DNA and RNA) store genetic information. Understanding these organic constituents is crucial in biochemistry, nutrition, and medicine.