Just as glucose was broken down in cellular respiration, other molecules undergo catabolism. Fat breaks down into glycerol and three fatty acids. Glycerol is converted to PGAL, a metabolite in glycolysis. Amino acids break down into carbon chains and amino groups. Hydrolysis of proteins results in amino acids.
Carbon chain is produced in liver by removal of the amino group.
ATP produced during catabolism drives anabolism. Substrates making up pathways can be used as starting materials for synthetic reactions. Molecules used for biosynthesis constitute metabolic pool. PGAL converts to glycerol, acetyl groups join to form fatty acids. Some metabolites can be converted to amino acids by transamination, transfer of an amino acid group to an organic acid.