Final answer:
Hydrochloric acid (HCl) in gastric juice is the chemical that kills bacteria consumed with food, creating an acidic environment with a pH of 1.0 to 2.5 and destroying most pathogens.
Step-by-step explanation:
The chemical in gastric juice that kills bacteria you may have consumed is hydrochloric acid (HCl). This substance is secreted by the glands in the stomach lining and creates a highly acidic environment with a pH of about 1.0 to 2.5. This low pH level denatures proteins in food, making them easier for enzymes to break down, and also serves as a protective mechanism by killing most pathogens that enter the stomach with food or water. While pepsin is an enzyme that breaks down proteins into amino acids, and amylase and lipase are enzymes that digest carbohydrates and fats respectively, it is the hydrochloric acid that is responsible for creating an environment that is inhospitable to bacteria, thereby protecting the body from many ingested pathogens.
It is important to note that other substances mentioned, such as amylase, pepsin, and bile, have different roles in digestion. Amylase is found in the mouth and begins the chemical digestion of carbohydrates, pepsin is a gastric enzyme that hydrolyzes protein into smaller peptides, and bile is produced by the liver and helps in the digestion of fatty acids. However, only hydrochloric acid is directly involved in the acidic environment that kills bacteria.