IGCSEScienceCambridge (CIE)Combined ScienceBiologyRevision Notes7. Human NutritionHuman Diet & DigestionHydrochloric Acid

Hydrochloric Acid (Cambridge (CIE) IGCSE Combined Science): Revision Note

Exam code: 0653

Lára Marie McIvor

Last updated

Cambridge (CIE) Combined Science: BiologyCambridge (CIE) Biology

Hydrochloric Acid: Extended

  • The stomach produces several fluids which together are known as gastric juice

  • One of the fluids produced is hydrochloric acid

  • This kills bacteria in food and gives an acid pH for enzymes to work in the stomach

How is a low pH helpful in the stomach?

  • The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells, meaning they cannot carry out any cell reactions to maintain life

  • Pepsin, produced in the stomach, is an example of an enzyme which has a very low optimum pH - around pH 2

  • The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate

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    Lára Marie McIvor

    Author: Lára Marie McIvor

    Expertise: Biology, Psychology & Sociology Subject Lead

    Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.