Organisation and the digestive system

• Levels of organisation


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


  Building blocks of life
• Tissues


  Groups of cells that have similar structures and functions
• Organs


  Groups of tissues working together to perform a specific function
• Organ systems


  Groups of organs working together, forming an organism
• Organisms


  A living thing
• Enzymes


  Large proteins that catalyse (speed up) reactions
• Enzymes


  • They are not changed in the reactions they catalyse
  • They only catalyse specific reactions
• Lock and key theory

  1. The enzyme's active site is a specific shape

  2. The enzyme (the lock) will only catalyse a reaction with a specific substrate (the key) that fits into its active site

  3. At the active site, enzymes can break down molecules into smaller ones or join smaller molecules together to form larger ones

  4. When the products have been released, the enzyme's active site can accept another substrate molecule
• Parts of the digestive system

  • mouth
  • salivary glands
  • oesophagus
  • stomach
  • liver
  • gall bladder
  • pancreas
  • small intestine
  • large intestine
  • rectum
  • anus
• Digestive enzymes


  Enzymes that convert food into small, soluble molecules that can be absorbed into the bloodstream
• Digestive enzymes


  • amylase
  • proteases
  • lipases
• Amylase


  Enzyme that breaks down starch into glucose
• Proteases


  Enzymes that break down proteins into amino acids
• Lipases


  Enzymes that break down lipids into fatty acids and glycerol
• As temperature increases


  The rate of enzyme-catalysed reactions increases
• At very high temperatures


  Enzymes become denatured and stop working
• Denaturation


  The shape of an enzyme's active site is changed, so the substrate can no longer fit into it
• Optimum pH


  The pH value at which an enzyme works best
• Optimum temperature


  The temperature at which an enzyme works fastest