CAIE IGCSE Biology 7.4.5 Hydrochloric Acid in Gastric Juice

Practise explaining how hydrochloric acid in gastric juice creates the acidic conditions for pepsin activity and helps protect the stomach from swallowed microorganisms.

Exam points

state that hydrochloric acid gives stomach protease or pepsin its optimum acidic pH
explain that stomach acid kills or denatures harmful microorganisms swallowed with food
use a low-pH enzyme-activity graph to infer that the enzyme acts in the stomach

[Maximum number: 2]

Cells in the lining of the stomach secrete gastric juice, which contains hydrochloric acid and pepsin.

State two roles of hydrochloric acid in the stomach.

1
2

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7.4.5—Functions of hydrochloric acid question 1