Question

Proteins are broken down into amino acids in _______.
(A)Buccal cavity
(B)Stomach
(C)Intestine
(D)Rectum

Answer 1

Hint: Protein is a very important nutrient in our food but the dietary protein is too large to be absorbed directly by our cells. Therefore, its digestion occurs in the alimentary canal to break it into small amino acid molecules that can be absorbed by our body.

Complete answer:
Proteins are digested into small peptides and amino acids in the small intestine before they get absorbed. The breakdown of protein molecules begins in the stomach and continues to the small intestine where enzymes like trypsin and chymotrypsin from the pancreas and carboxypeptidase act on it to completely digest it into amino acids.

Additional Information:
Protein digestion starts in the stomach with the help of the pepsin enzyme. It is produced in the chief cells of the stomach lining and gets secreted in the stomach when food enters it. The proenzyme pepsinogen upon mixing with the HCL in the gastric juice activates and transforms into pepsin. It reduces the protein molecules into peptides.
When the food enters into the duodenum part of the intestine from the stomach, proteolytic enzymes trypsin and chymotrypsin from the pancreas acts on it and cleaves it further into smaller peptides. The pancreatic brush border releases the enzyme carboxypeptidase that splits these into amino acid molecules. Thus the digestion of protein takes place in the alimentary canal.

So, the correct answer is "Intestine".

Note: In the buccal cavity, only a small portion of carbohydrates and fats gets digested. In the stomach, cleavage of proteins and carbohydrates occurs. Most of the digestion activity occurs in the small intestine with the help of gallbladder secretion and its own enzymes. Pancreatic lipase and bile from the liver help in fat digestion. Carbohydrates get broken down to glucose by the action of amylase and salivary enzymes.