Protein digestion begins in theMultiple Choicestomach.mouth.esophagus.small intestine.large intestine.

Analysis of the Question

To determine where protein digestion begins, we need to understand the roles of the various parts of the digestive system: the stomach, mouth, esophagus, small intestine, and large intestine.

1. Mouth: The initial stage of digestion occurs here, where mechanical digestion takes place through chewing, and enzymes like salivary amylase start the digestion of carbohydrates, not proteins.

2. Esophagus: This is primarily a transport tube that moves food from the mouth to the stomach. No digestion occurs here.

3. Stomach: The stomach is where protein digestion begins. The acidic environment and the presence of gastric juices, especially pepsin, break down protein into smaller peptides.

4. Small Intestine: While protein digestion continues here with the help of pancreatic enzymes (like trypsin), it does not initiate the process.

5. Large Intestine: This organ's role is primarily in water absorption and does not involve protein digestion.

Conclusion

The most appropriate answer is that protein digestion begins in the stomach.

Final Answer

Protein digestion begins in the stomach.