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 form an organism
• Main nutrients in food

  • Carbohydrates
  • Protein
  • Lipids (fats)
• Digestion


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

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

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


  • Food chewed, enzymes in saliva begin to digest starch
• Esophagus


  • Food passes from mouth to stomach
• Stomach


  • Enzymes begin digestion of proteins, contains hydrochloric acid, churning action turns food into fluid
• Small intestine


  • Enzymes from pancreas and liver continue digestion, small food molecules absorbed into bloodstream
• Large intestine


  • Water absorbed, feces released
• Liver


  • Releases bile to aid digestion of lipids
• Pancreas


  • Releases enzymes to continue digestion of starch, protein and lipids
• Products of digestion used by body to build new carbohydrates, lipids and proteins
• Some glucose produced used in respiration
• 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 substrate
• Substrate does not fit into active site


  Enzyme cannot break down 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