Flavin adenine dinucleotide (FAD) is a coenzyme found in all living cells. It plays a crucial role in various biological processes, particularly in the metabolism of carbohydrates and fats. FAD is involved in redox reactions, where it alternates between oxidized and reduced forms, facilitating the transfer of electrons in cellular respiration. FAD is derived from the vitamin riboflavin (vitamin B2) and is essential for the function of several enzymes, known as flavoproteins. These enzymes are important for energy production and the synthesis of important biomolecules. FAD's ability to accept and donate electrons makes it vital for maintaining cellular energy levels.