Some of the important functions of HCl are:
(i) Kills ingested bacteria.
(ii) Provides acidic medium for protein digestion.
(iii) Converts inactive pepsinogen and pro-rennin into active pepsin and rennin respectively.
(iv) Regulates opening closing of pyloric sphincter.
(v) Prevents putrefaction of food in stomach.
(vi) Excess secretion of HCl damages gastric mucosa and causes gastric and duodenal ulcers.
(vii) HCl splits nucleoproteins into nucleic acids and proteins.