Organisation

• 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 organisms
• 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
• Enzymes


  Catalyze chemical reactions, speed them up
• 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
• Enzymes


  • Large protein molecules
  • Have a groove on their surface called the active site
  • The active site is where the substrate attaches
• Some glucose produced is used in respiration
• 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
• Proteases


  • Found in stomach, pancreatic fluid, small intestine
• Proteins


  Long chains of amino acids
• Starch digestion


  Carbohydrases (amylase) break down starch into simple sugars
• Amylase


  • Found in saliva, pancreatic fluid
• Starch


  Chain of glucose molecules
• Lipid digestion


  Lipase breaks down lipids into glycerol and fatty acids
• Lipase


  • Found in pancreatic fluid, small intestine
• Lipids


  Molecule of glycerol attached to three fatty acids
• Bile


  • Made in liver, stored in gallbladder
  • Not an enzyme, but helps speed up lipid digestion by lipase
  • Converts large lipid droplets into smaller droplets (emulsifies)
  • Alkaline, neutralizes stomach acids
• Enzyme


  Speeds up chemical reactions by having a groove on their surface called the active site
• Substrate


  The molecule that the enzyme reacts with, fits perfectly into the active site
• Lock and key theory

  The substrate must fit perfectly into the active site
• Effect of temperature on enzyme activity

  1. Gradually increase temperature

  2. Measure enzyme activity (rate of reaction)

  3. Activity increases as temperature increases

  4. Reach optimum temperature

  5. Activity rapidly decreases past optimum temperature
• Optimum temperature


  The temperature at which the enzyme is working at the fastest possible rate, maximum frequency of successful collisions between substrate and active site
• Denaturation


  At high temperatures, the enzyme molecule vibrates and the shape of the active site changes, so the substrate no longer fits perfectly
• Effect of pH on enzyme activity

  1. Alter pH

  2. Measure enzyme activity (rate of reaction)

  3. Activity is maximum at optimum pH

  4. Activity drops to zero if pH is too acidic or too alkaline
• Optimum pH


  The pH at which the enzyme activity is maximum
• Enzymes with different optimum pH

  • Protease enzyme in stomach (acidic pH)
  • Lipase enzyme from pancreas (alkaline pH)