When food enters the mouth it is chewed and mixed with saliva. Saliva contains amylase which hydrolyses starch to maltose.The food is swallowed and enters the stomach. The acid denatures amylase and no carbohydrate digestion takes place in the stomach.The food (chyme) enters the duodenum. It mixes with the alkaline pancreatic juice secreted by the pancreas. The pH of pancreatic juice is 8.5 and neutralises the food. Pancreatic amylase continues the hydrolysis of the remaining starch to maltose.The food is pushed towards the ileum by a muscular action called peristalsis. The epithelial lining of the ileum produces the membrane-bound enzyme maltase which hydrolyses maltose to alpha-glucose.Sucrose is hydrolysed by sucrase to glucose and fructose. Lactose is hydrolysed by lactase to glucose and galactose.
Carbohydrate Digestion
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Specification: AQA Biology (7401), AS-level, 3.3.3 Digestion and absorption. Topic: Digestion.
Key terms in this lesson
- hydrolysis
- The breaking of a covalent bond within a molecule using a water molecule.
- peristalsis
- Waves of muscular contraction that push food along the gut.
More in Digestion
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- The Digestive System
- Lipid Digestion
- Protein Digestion
- Structure of the Ileum
- Absorption of Amino Acids
- Absorption of Monosaccharides
- Absorption of Triglycerides
All 10 lessons in Digestion · All AQA AS-level Biology topics