| Major parts of the digestive system | - Salivary glands
- Oesophagus
- Stomach
- Pancreas
- Ileum
- Large intestine
- Rectum |
| Oesophagus | - Carries food from the mouth to the stomach |
| Stomach | - Muscular sack
- Inner layer has glands, produces enzymes
- Stores + digests food, especially proteins |
| Ileum | - Long muscular tube
- Food digested by enzymes
- Has villi |
| Large intestine | - Absorbs water |
| Rectum | - Final section of intestines
- Where faeces are stored
- Removed via anus, called egestion |
| Salivary glands | - Near mouth
- Secretes amylase, hydrolyses starch into amylose |
| Pancreas | - Large gland below stomach
- Produces pancreatic juice
- Contains protease, lipase and amylase |
| What is digestion | Two stages
- Physical breakdown
- Chemical breakdown |
| Physical breakdown | - Teeth breaks down large molecules into smaller ones
- So food can be ingested
- LSA for chemical digestion
- Food churned by muscles in stomach |
| Chemical breakdown | - Hydrolysis of large insoluble molecules into smaller soluble ones
- Enzymes hydrolyse molecules, adding water |
| Types of enzymes | - Carbohydrase/amylase
- Lipase
- Protease |
| Carbohydrase | - Hydrolyses carbohydrates into monosaccharides
- Made by pancreas, small intestine, salivary glands |
| Lipase | - Hydrolyses lipids into glycerol + fatty acids
- Made by pancreas, small intestine |
| Protease | - Hydrolyses proteins into amino acids
- Made by pancreas, small intestine, stomach |
| Membrane-bound disaccharidases | - Enzymes attached to cell membranes of epithelial cells lining the ileum
- Helps break down disaccharides into monosa. |
| Carbohydrate digestion (1) | - Salivary amylase in the mouth hydrolyses starch (macromolecule) into maltose
- Breaking 1-4 glycosidic bonds |
| Carbohydrate digestion (2) | - Salivary amylase is denatured in the stomach |
| Carbohydrate digestion (3) | - After the stomach food then enters the small intestine where it mixes with pancreatic juice |
| Carbohydrate digestion (4) | - Pancreatic amylase hydrolyses starch |
| Carbohydrate digestion (5) | - There are maltase enzymes on epithelial cells of ileum |
| Carbohydrate digestion (6) | - These hydrolyse maltose to alpha glucose
- Glucose can be absorbed into the blood |
| Bile salts | - Produced by the liver
- Emulsifies lipids into small droplets |
| Importance of bile salts | - Small lipid droplets increases SA for lipase to work on |
| Peptidases | - Group of proteases
- Proteins are large, complex |
| The different peptidases | - Endopeptidases
- Exopeptidases
- Dipeptidases |
| Endopeptidases | - Breaks down specific amino acids in the middle of a polypeptide |
| Exopeptidases | - Break down specific amino acids at the end of a polypeptide |
| Dipeptidases | - Hydrolyses dipeptides into amino acids |
