Chemical Digestion - Stomach
Biology: Cambridge International GCSE Supplement, topic 7.4.5
Stomach Acid and Bile
Enzyme activity is affected by pH. Gastric juices in the stomach are acidic, and bile is alkaline.
Gastric juices
- Gastric juices in the stomach contains hydrochloric acid.
- The acidic conditions are optimum for the enzyme pepsin in the stomach.
- The hydrochloric acid kills harmful microorganisms that make it into the stomach in food by denaturing their enzymes.
Bile
- Bile is produced in the liver, stored in the gall bladder and released into the small intestine.
- Bile is alkaline so neutralises the acid in food that comes from the stomach, which creates an optimal pH for enzymes in the small intestine.
- Bile also breaks down large fat droplets into smaller fat droplets, which is called emulsification. This creates a larger surface area for lipases to break down the fats.
Test yourself on Chemical Digestion - Stomach
Which of these are true of gastric juices?
Gastric juices contain which acid?