Digestive System

• Tissue


  A group of cells with a similar structure and function
• Organ


  A group of tissues working together for a specific function
• Organ system


  Organs grouped together to peform a certain function
• Main nutrients in food

  • Carbohydrates
  • Protein
  • Lipids (fats)
• Digestion


  1. Large insoluble food molecules broken down into small soluble molecules by enzymes

  2. Small soluble molecules diffuse into bloodstream
• Main organs of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Liver
  • Pancreas
• Mouth


  • Food chewed, the enzyme amylase in saliva begin to digest carbs
• Oesophagus

  • Food passes from mouth to stomach, mechanical digestion happens with peristalsis
• Small intestine


  • Enzymes from pancreas (lipase, amylase) and liver (bile) continue digestion, small soluble food molecules absorbed into bloodstream
• Large intestine


  • Water absorbed, feces released
• Liver


  • Releases bile to which emulsifies and increases the surface area of lipids, making it easier for lipase to reach and digest it
• Pancreas


  • Releases the enzymes protease, amylase and lipase to continue digestion of carbs, protein and lipids
• Some glucose produced is used in respiration
• Stomach

  • The enzyme protease begins to break down protein
  • Filled with hydrochloric acid, which is the ideal pH for protease to work in
• Enzymes


  Catalyze chemical reactions, speed them up
• Enzymes


  • Large protein molecules
  • Have a groove on their surface called the active site
  • The active site is where the substrate attaches
• Substrate


  The molecule that the enzyme breaks down
• Substrate fits into active site


  Enzyme can break down the substrate
• Substrate does not fit into active site


  Enzyme cannot break down the substrate
• Lock and key theory


  Enzymes are specific, the substrate must fit perfectly into the active site
• Protein digestion


  Proteases break down proteins into amino acids
• Proteins


  • Long chains of chemicals called amino acids
• Starch digestion


  Amylase breaks down starch into simple sugars
• Starch


  A carbohydrate consisting of a chain of glucose molecules
• Lipid digestion


  Lipase breaks down lipids into glycerol and fatty acids
• Lipids


  Molecules consisting of glycerol attached to three fatty acids
• Bile


  Made in the liver, stored in the gallbladder, helps speed up lipid digestion by lipase
• Bile


  Converts large lipid droplets into smaller droplets, increasing surface area for lipase
• Bile


  Alkaline, neutralizes stomach acids, creates alkaline conditions for lipase in small intestine
• Small intestine


  The part of the digestive system where the products of digestion are absorbed into the bloodstream
• Small intestine


  • Very long (around 5 meters in humans)
  • Covered with millions of villi
  • Villi have micro villi to further increase surface area
  • Good blood supply to remove products of digestion
  • One cell thick membrane under villi for short diffusion path
• The features of the small intestine enable a rapid rate of diffusion of the products of digestion into the bloodstream
• Test for glucose

  • Use benedicts to test tube with sample
  • Place in water bath above 65’ for 5 minutes
  • Turns from blue to red
• Test for starch

  • Put iodine in test tube along with sample
  • Shake gently
  • Goes from orange to blue/black
• Test for lipids

  • Put ethanol in test tube along with sample
  • Will go from colourless to cloudy
• Test for proteins

  • Put biurets in test tube along with sample
  • Will go from blue to purple