Digestive system

• Digestive enzymes


  • Proteases
  • Lipases
  • Amylases
• Proteases


  Break down proteins into amino acids
• Lipases


  Break down fats into fatty acids and glycerol
• Amylases


  Break down carbohydrates into glucose
• Absorption of nutrients happens in the small intestine through the villi which have a large surface area
• Amylase


  Digestive enzyme
• Lipase


  Digestive enzyme
• Bile


  Digestive enzyme
• Enzyme


  Protein made by the digestive system that breaks down insoluble food molecules into soluble ones
• Enzymes


  • Have a specific shape that fits the substrate
  • Affected by temperature (optimum 40°C) and pH (4-11)
• Active site


  The part of the enzyme that the substrate binds to
• Substrate


  The molecule that the enzyme acts on
• Carbohydrates


  Made up of simple sugars
• Lipids


  Made up of fatty acids and glycerol
• Proteins


  Made up of amino acids
• Test for carbohydrates (starch)


  1. Add iodine solution

  2. Turns blue/black if starch present
• Test for sugars


  1. Add Benedict's solution

  2. Turns brick red if sugars present
• Test for lipids


  1. Add ethanol

  2. Gives cloudy white layer if lipids present
• Test for proteins


  1. Add Biuret reagent

  2. Turns purple if proteins present
• Carbohydrate digestion


  • Starch
  • Amylase
  • Maltose
  • Glucose
• Starch digestion


  1. Starts at the mouth

  2. Completed at the small intestines
• Starch digestion


  1. Starch is initially broken down to maltose by amylase from salivary glands

  2. Amylase from the pancreas completes the breakdown of starch to maltose in the small intestine

  3. Maltose is then broken down to glucose
• Protein digestion


  • Pepsin
  • Trypsin
  • Amino acids
• Protein digestion


  1. Starts at the stomach

  2. Protein is broken down by the enzyme pepsin in acidic conditions

  3. Completed at the small intestine where trypsin breaks the small chains of amino acids into amino acids
• Lipid digestion


  • Lipase
  • Fatty acids
  • Glycerol
• Lipid digestion


  1. Only takes place in the small intestine

  2. Lipase breaks down lipids into fatty acids and glycerol