Protein synthesis is an anabolic reaction because these reactions build molecules while catabolic ones break them down. Thanks to this we know that protein synthesis is anabolic.
Step-by-step explanation:
Anabolism relates to the process in cells where large macromolecules are formed up from miniature ones. In this case here, protein structure uses other proteins and amino acids (proteins' monomers) to make extra proteins, and so that is the accumulation of a large molecule, and accordingly studied anabolism.
Catabolism is the reverse of anabolism. An example would be the separation of proteins in food to amino acids for digestion. In this case, a large particle (a protein) is split down into miniature dispersible molecules (amino acids).