digestion enzymes

• Lipids (fats and oils) are large molecules. During digestion the enzyme lipase breaks them down into fatty acids and glycerol (energy store) . These can be used by the body to provide energy.

  
• Proteins are long chains of amino acids. During digestion the enzyme protease breaks them down into single amino acids (growth) which are small and soluble and can be used by cells to build new proteins.

  
• Starch is a long chain carbohydrate. It is insoluble. During digestion the enzyme carbohydrase (amylase) breaks it down into single molecules of glucose (energy store) which are small and soluble enough to be carried in the blood to the cells for respiration, or to be stored as glycogen in the liver.

  
• Testing for Starch

  Method

  1. Place 2cm³ of starch in a test tube

  2. Add two drops of iodine solution

  Result : Iodine solution turns orange/brown to blue black
• Testing for Glucose

  Method

  1. Place 2cm³ of glucose in a test tube
  2. Add two drops of Benedicts reagent and heat to 80°C in a thermostatically controlled water bath for 5 minutes
  3. Result : Benedict's Reagent turns blue to orange (the more redder, the more glucose added)
• Testing for Protein

  Method

  1. Place 2cm of protein in a test tube
  2. Add two drops of Biuret solution
  3. Result : Biuret solution turns Blue to Lilac purple
• Lipids are in oily fish, nuts and seeds, and avocados. They also keep us warm by insulating us and protect our organs
• Proteins are found in legumes and meat/fish. Proteins can be used for energy if we don't have enough carbs or lipids
• Visking tubing limitations ;

  • No blood supply so diffusion gradient cannot be maintained
  • No villi - surface area is too small
  • Too short - tubing should be 6m long