What are proteins broken down into during digestion?

• A. Amino acids
• B. Peptides/ Amino Acids
• C. Nucleotides
• D. Simple sugars

Answer: (B)

Proteins are too large to be absorbed as they are, so they’re broken down into smaller units by digestive enzymes. In the stomach, acid and pepsin start the process, and in the small intestine pancreatic proteases along with brush-border peptidases finish breaking things down. The result is short peptides and amino acids, with the amino acids being the primary absorbed products (peptides can be absorbed too, then further hydrolyzed inside intestinal cells). This is why the best description is peptides and amino acids as the products of protein digestion. Nucleotides come from nucleic acids, and simple sugars come from carbohydrates, not proteins.