Metabolism is the sum total of anabolism and catabolism. Therefore, biotin is essential for amino acid catabolism, gluconeogenesis, and fatty acid metabolism. Biotin is important in fatty acid synthesis, branched-chain amino acid catabolism, and gluconeogenesis. ATP acts as a bridge between catabolism and anabolism. Other means include the degradation of glycogen (glycogenolysis) and fatty acid catabolism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion. This is like the forces of anabolism and catabolism in the human body. Amino acid catabolism results in waste ammonia. In biology, enzymes are protein-based catalysts in metabolism and catabolism. The Leloir pathway is a metabolic pathway for the catabolism of -galactose. The end-product of catabolism of protein metabolism in animals is nitrogen. BPA can also affect the metabolism or the catabolism of sex hormones. Humans obtain glutamine through catabolism of proteins in foods they eat. This is a common pathway during amino acid catabolism. However, the main steps of fatty acids catabolism occur in the mitochondria.