Question

Why does the small intestine require an alkaline pH?

Answer 1

The duodenum, jejunum, and ileum are the three sections of the small intestine. It aids in the digestion of meals from the stomach. It absorbs nutrients (vitamins, minerals, carbs, fats, proteins), as well as water, from meals so that the body may use them.

Complete answer:
The digestive system includes the small intestine.
Because of the enzymes present, as well as the risk for harm to the gut lining.
It is an important part of the digestive process. It accomplishes this by using enzymes to break down complicated molecules into simpler ones. However, all enzymes require specific circumstances in order to function.
Enzymes function because they have highly precise structures - active sites - that only allow certain substances to bind to them (and therefore be affected). The enzyme gets less efficient at higher temperatures or pH levels until it can no longer function. The enzyme is said to be denatured.
The enzymes that "work" in the small intestine require an alkaline pH in order to function well.
Another explanation is that powerful acids (such as hydrochloric acid) might harm the gut lining. The stomach has been uniquely designed to deal with these conditions (thick lining, routinely replaced cells, etc), but the small intestine has not. As a result, the pH must be decreased to avoid harm.
Finally, bile, an alkaline material produced by the liver, is used to modify the pH of the small intestine. Bile is required because the hydrochloric acid used in the earliest stages of digestion causes food to become overly acidic when it leaves the stomach.
Bile is secreted into the small intestine, where it serves two functions: It neutralises acid and provides the alkaline conditions that the small intestine requires. It emulsifies fats, allowing the lipase enzymes to function across a greater surface area.

Note:-
The intraluminal pH changes quickly in the duodenum, from very acidic in the stomach to roughly pH 6. The pH of the small intestine gradually rises from pH 6 to around pH 7.4 in the terminal ileum. In the caecum, the pH lowers to 5.7, then progressively rises again, reaching pH 6.7 in the rectum.