Final answer:
This question is about the digestion of proteins and the role of pepsin in this process.
Step-by-step explanation:
The subject of this question is Biology. Specifically, it relates to the digestion of proteins in the human body.
Proteins are denatured in the stomach, where the enzyme pepsin converts pepsinogen to its active form. This conversion is necessary for the digestion of dietary proteins. Additionally, pepsin secretion is required for the coupling of intrinsic factor and vitamin B12, which is essential for its absorption in the small intestine.
In summary, the subject of this question is Biology, and it is related to the digestion of proteins and the role of pepsin in this process.