Question

there is acidic medium in stomach whereas alkaline medium in small intestine why is it important to have such difference in the pH and which secretions are responsible for maintaining these different pH levels in stomach and small intestine

Answer 1

In stomach , acidic environment is due to HCl , (hydrochloric acid)

When the partly digested food called chyme from stomach enters intestine another set of enzymes will now act upon it, but they aren't active in acidic environment. So alkaline environment is necessary, and this is brought about by bile juice.