where does the chemical digestion of proteins begin?
Confidence votes 106. Protein digestion in humans begins in the stomach. The enzyme pepsin is activated from its' inactive form pepsinogen due to the acidic conditions of the stomach. Pepsin starts digestion of proteins by breaking down the many of polypeptides into shorter peptides. However, complete chemical digestion will not occur until proteins reach the duodenum and the jejunum of the small intestine. Here more enzymes come into play (proteases and peptidases) so that the protein is completely broken down into its' smallest building blocks (the monomers called amino acids).