"Biotin, also known as Vitamin H or Coenzyme R[2], is a water-soluble B-complex vitamin (vitamin B7). It is 
composed of a ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is a coenzyme in the synthesis of fatty acids, isoleucine, and valine, and it plays a role in gluconeogenesis."
"Biotin is necessary for cell growth, the production of fatty acids, and the metabolism of fats and amino acids. It plays a role in the citric acid cycle, which is the process by which biochemical energy is generated during aerobic respiration. Biotin not only assists in various metabolic reactions but also helps to transfer carbon dioxide. Biotin may also be helpful in maintaining a steady blood sugar level.[3] Biotin is often recommended for strengthening hair and nails.[citation needed] As a consequence, it is found in many cosmetics and health products for the hair and skin, though it cannot be absorbed through the hair or skin itself."