Organization

• 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

  • Chemicals from liver and pancreas continue digestion of starch, protein and lipids
  • Small food molecules absorbed into bloodstream
• Large intestine

  • Water absorbed, feces released
• Liver

  • Releases bile to aid digestion of lipids, neutralizes stomach acid
• 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 is 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

  1. Proteases in stomach, pancreatic fluid and small intestine

  2. Convert proteins to individual amino acids
• Proteins

  Long chains of chemicals called amino acids
• Starch digestion

  1. Carbohydrases, specifically amylase in saliva and pancreatic fluid

  2. Break down starch into simple sugars
• Starch


  Chain of glucose molecules
• Lipid digestion

  1. Lipase in pancreatic fluid and small intestine

  2. Breaks down lipids into glycerol and fatty acids
• Lipids

  Molecule of glycerol attached to three molecules of fatty acids
• Bile

  • Made in the liver, stored in the 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)
• 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 that further increase surface area
  • Good blood supply to remove products of digestion
  • Thin membrane under villi for short diffusion path
• Absorption of products of digestion in small intestine

  1. Diffusion of molecules that can be absorbed this way

  2. Active transport for molecules that cannot be absorbed by diffusion