Digestion (AQA A Level Biology)

The Process of Digestion

• Digestion is a process in which relatively large, insoluble biological molecules in food (such as starch, proteins) are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into the bloodstream and delivered to cells in the body

• Enzymes are essential for the process of digestion as they catalyse the hydrolysis

• These small soluble molecules (such as glucose and amino acids) are used either to provide cells with energy (via respiration) or to build other molecules for cell growth, repair and function

• Proteins are hydrolysed into amino acids

• Carbohydrates are hydrolysed into simple sugars

• Lipids are hydrolysed into a mixture of glycerol and fatty acids

Human Digestive System

• The human digestive system includes the following:

  • Glands - the salivary glands and glands in the pancreas produce digestive juices

  • The stomach and small intestine - the sites of digestion

  • The liver - produces bile

  • Small intestine - the site of absorption

  • Large intestine - site of water reabsorption

Digestive System Table

The human digestive system