Digestion (AQA AS Biology): Revision Note
Exam code: 7401
Digestion
During digestion, large biological molecules are hydrolysed to smaller molecules that can be absorbed across cell membranes
Proteins are hydrolysed into amino acids
Carbohydrates are hydrolysed into simple sugars
Lipids are hydrolysed into glycerol and fatty acids
The resulting small molecules are used by the cells to:
release energy via respiration
build new molecules for cell growth, repair and function
Examiner Tips and Tricks
The AQA specification does not require students to know details of the structure of the digestive system; the information below has been included to provide context for the locations of enzyme and bile production and the conditions under which enzymes will be acting.
Human digestive system
The human digestive system is an organ system that contains a series of organs that work together to digest and absorb food
Structure | Function |
|---|---|
Mouth and salivary glands | Food is ingested and teeth break it down into smaller pieces Saliva is secreted into the mouth The enzyme amylase in begins to digest starch into maltose |
Stomach | Protease enzymes begin protein digestion Hydrochloric acid provides a suitable pH for enzymes and destroys any pathogens in food |
Liver | Bile salts are produced here Bile salts aid the digestion of lipids, as well as neutralising stomach acid as it exits the stomach |
Pancreas | Amylase, protease and lipase enzymes are produced here before being released into the duodenum |
Small intestine: duodenum | The acidic stomach contents are neutralised by bile and become slightly alkaline Enzymes complete chemical digestion here |
Small intestine: ileum | Food and water are absorbed into the blood via villi in the lining of the ileum |
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