B3 - Organisation and the digestive system

• Levels of organisation in animals


  • cells
  • tissues
  • organs
  • organ systems
  • organisms
• cells


  basic building blocks
• tissues


  groups of cells that work together to perform a similar function
• organs


  groups of tissues working together to perform a similar function
• Organ systems


  groups of organs working together to perform a similar function
• Organisms


  organ systems working together
• Mouth


  where food is chewed
• Salivary glands


  produces saliva containing the enzyme amylase
• Oesophagus


  Carries food to the stomach
• Stomach


  • churns food
  • digests proteins
  • releases hydrochloric acid which kills pathogens
• Gall bladder


  • stores bile
• Bile


  an alkaline that neutralises hydrochloric acid froom the stomach and emulsifies fat to form small droplets with a large surface area
• Liver


  produces bile
• Pancreas


  produces the enzymmes amylase, lipase and protease
• Small intestine


  where digested food is absorbed into the blood
• Large intestine


  where water and minerals are absorbed into the blood
• Rectum


  stores faeces
• Anus


  expels faeces
• Enzymmes


  • large proteins that catalyse reactions
• Lock and key theory


  • the enzyme's active siite is a specific shape
  • the enzyme (the lock) will only catalyse a specific reaction because only the substrate (the key) fits into its active site
  • at the active site, enzymes can break molecules down into smaller ones or bind smaller molecules to form larger ones
  • when the products have been released, the enzyme's active site can accept another substrate molecule
• The effect of temperature on enzymes


  • as temperature increases, the rate of reaction increases
  • enzyme and substrate molecules move around faster and collide more frequently
  • the reaction works as fast as possible at the optimum temperature
  • after the optimum, the enzyme denatures and stops working
• The effect of pH on enzymes


  • different enzymes have different optimum pH values
  • this allows enzymes to be adapted to work well in environments with different pH values
• Denaturation


  • at extremes of pH or very high temperatures, the shape of an enzyme's active site can change
  • the substrate can no longer bind to the active site, so the enzyme cannot catalyse the reaction
  • the enzyme has been denatured
• Amylase


  • Produced in the:
  • salivary glands
  • pancreas
  • small intestine
  • Reaction catalysed:
  • starch - glucose
• Protease


  • Produced:
  • stomach
  • pancreas
  • small intestine
  • Reaction catalysed
  • proteins - amino acids
• Lipase


  • Produced:
  • pancreas
  • small intestine
  • Reaction catalysed
  • lipids - fatty acids and glycerol
• Test for lipids


  • ethanol
  • colour change from colourless to cloudy
• Test for sugars

  • Benedict's
  • colour change from blue to red
• Test for starch


  • iodine
  • colour change from brown to blue-black
• Test for protein

  • biuret reagent
  • colour change from blue to purple