Enzymes in Digestion

• Describe how digestive enzymes are produced and how they work

  • Digestive enzymes are produced by specialised cells in glands , and in the lining of the gut 
  • The enzymes pass out of the cells into the digestive system 
  • They come into contact with food molecules 
  • They then catalyse the breakdown of large insoluble food molecules into smaller soluble molecules

  
• What is protease

  • Protease is a digestive enzyme produced in the stomach , small intestine and pancreas 
  • It breaks down protein into amino acids or peptides

  
• Explain what happens when protease breaks down proteins

  • Proteins are long chains of amino acids 
  • When we digest proteins , the protease enzymes convert the protein back to the individual amino acids , which are absorbed into the bloodstream  
  • The amino acids are then absorbed by body cells , where they are joined together in a different order to make human proteins

  
• What is amylase

  • Amylase is a digestive enzyme and it is produced in the salivary glands and the pancreas (or pancreatic fluid)
  • Amylase is a carbohydrase , and it breaks down starch into maltose (sugar) 
  • (Carbohydrases break down carbohydrates, but when speaking about starch , the carbohydrase is called amylase)

  
• Explain what happens when amylase breaks down starch

  • Starch consists of a chain of glucose molecules 
  • When starch (or any other carbohydrates) are digested , amylase enzymes (or other carbohydrase enzymes) break it down into simple sugars

  
• What is lipase

  • Lipase is a digestive enzyme and it is produced in the pancreas and small intestine 
  • It breaks down lipids (fats) into fatty acids and glycerol

  
• Explain what happens when lipase breaks down lipids

  • A lipid molecule consists of a molecule of glycerol attached to 3 molecules of fatty acids 
  • When lipid molecules are digested, they are broken down by lipase enzymes, and this produces fatty acids and glycerol

  
• What are the products of digestion used for

  To build new carbohydrates , lipids and proteins - Some glucose is used in respiration
• Where is starch digested in the body

  In the mouth and the small intestine

  
• Where is protein digested in the body?

  The stomach and the small intestine

  
• Where are fats/lipids digested in the body

  In the small intestine

  
• Why is starch not digested in the stomach?

  • The stomach doesn’t produce amylase 
  • The conditions in the stomach are too acidic for the amylase to work