Q.What would happen if HCl were not secreted in the stomach?

Hydrochloric acid (HCl), secreted by the oxyntic (parietal) cells of the gastric glands, plays two essential roles in the stomach. If it were not secreted:

• Protein digestion in the stomach would fail to start. HCl is required to convert the inactive pepsinogen into active pepsin; without HCl, pepsinogen would remain inactive, and the stomach would be unable to digest dietary proteins into proteoses and peptones. The knock-on autocatalytic activation of further pepsinogen would also not occur.
• The stomach would lose its strongly acidic (bactericidal) environment. The normal acidity (around pH 1.8) helps kill many of the bacteria and other microorganisms ingested with food; without HCl, this protective function would be lost, raising the risk of gut infections.
• The optimal, strongly acidic pH that gastric pepsin needs to work efficiently would also be absent, so even any pepsin that did somehow form would not digest protein effectively. …

Trace HCl's two functions forward to their consequences if absent: (1) no activation of pepsinogen → no gastric protein digestion, and (2) no acidic environment → …

• Only mentioning the digestive consequence (no pepsin activation) and forgetting HCl's antiseptic, germ-killing role. …