Question

Which of the following is incorrect regarding the given digestion and absorption of protein?
A. The breakdown of proteins to peptides is catalyzed by pepsin in the stomach and by the pancreatic enzymes trypsin and chymotrypsin in the small intestine.
B. Peptides are broken down into amino acids by pancreatic carboxypeptidase and intestinal aminopeptidase.
C. Small peptides consisting of two or three amino acids can diffuse through epithelial cells and break down into carbon dioxide and ammonia which are released into the blood.
D. None of these

Answer 1

Proteins are large biomolecules which are needed by the human body for a variety of functions. Any protein molecule is made of a chain of structural and functional units known as amino acids. Digestion and absorption of proteins are facilitated by a combined action of several enzymes that act as catalysts during the process.

Complete answer:
During the digestion of proteins or peptides, the process that takes place is the conversion of big protein molecules into smaller components known as Amino acids. During this process a number of enzymes work simultaneously to catalyze the process. . The enzymes that carry out this process are pepsins that initiate the digestion in the stomach. Trypsin, chymotrypsin and procarboxypeptidase continue the digestion in the small intestine and break it down further. Finally amino acids are formed from dipeptides by the action of dipeptidases in the intestine and the absorption starts from the small intestine.
Therefore peptides are not broken into amino acids by the pancreatic carboxypeptidase and intestinal aminopeptidase.
Considering the other given options:
A. Pepsin enzyme initiates the digestion of protein in the stomach, further it is digested more in the small intestine by trypsin and chymotrypsin. Thus it is a correct statement.

C. After diffusion into the epithelial cells of the intestine, the end products of breaking down the peptides are CO2 and ammonia, which are the waste products and released into the blood for elimination. Thus it is a correct statement.

So, the correct answer is “Option B”.

Note:
Proteins play a major role in the structural as well as molecule level functioning of the body. It also forms different molecules in the body such as antibodies, enzymes, and hormones. Deficiency of proteins can cause a variety of deficiency diseases such as Marasmus that can be fatal.