Organisation

• Cells are the basic building blocks that make up all living organisms
• Specialised cells carry out a particular function
• Differentiation


  The process by which cells become specialised for a particular job
• Differentiation


  Occurs during the development of a multicellular organism
• Specialised cells form


  • Tissues
  • Organs
  • Organ systems
• Large multicellular organisms (e.g. humans) have different systems inside them for exchanging and transporting materials
• Tissue


  A group of similar cells that work together to carry out a particular function
• Tissues in mammals (like humans)

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Epithelial tissue


  • Covers some parts of the body, e.g. the inside of the gut
  • Less than 0.1 mm
• Tissues


  Organised into Organs
• Organ


  A group of different tissues that work together to perform a certain function
• Tissues in the stomach

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Goorg


  • About 10 cm
  • Over 1000 times longer than an epithelial cell
• Organ System


  A group of organs working together to perform a particular function
• Organs in the digestive system

  • Glands (e.g. pancreas and salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• Organ systems work together to make entire organisms
• Cells are organised into tissues, tissues into organs, organs into organ systems
• Enzymes


  Catalysts produced by living things that control chemical reactions
• Enzymes


  • They increase the speed of reactions without being changed or used up
  • They only speed up useful reactions, not unwanted ones
• Active site


  The unique shape of an enzyme that fits the substance it acts on (the substrate)
• Substrate fits enzyme's active site

  Reaction is catalysed
• Enzymes actually change shape when the substrate binds to get a tighter fit (induced fit model)
• Eyes


  Clever but not very versatile, need just the right conditions to work properly
• Enzymes


  Need the right temperature and pH level to work properly
• Changing the temperature


  Changes the rate of an enzyme-catalysed reaction
• Higher temperature


  Increases the rate of reaction at first
• Denaturation


  When the temperature gets too high, some of the bonds holding the enzyme together break, changing the shape of the active site so the substrate won't fit anymore
• Optimum temperature


  The temperature where the enzyme is most active
• pH


  If it's too high or too low, it interferes with the bonds holding the enzyme together, changing the shape of the active site and denaturing the enzyme
• Optimum pH


  The pH that the enzyme works best at, often neutral pH 7 but not always
• Pepsin


  • An enzyme used to break down proteins in the stomach, works best at pH 2
• Most enzymes catalyse just one reaction
• The optimum temperature for most human enzymes is around normal body temperature
• Stomach enzymes work best at low pH but the enzymes in the small intestine like a higher pH
• Investigating the effect of pH on enzyme activity


  1. Put a drop of iodine solution into every well of a spotting tile

  2. Heat water to 35°C in a beaker over a Bunsen burner

  3. Add amylase solution and buffer solution with pH 5 to a boiling tube, let it sit for 5 minutes

  4. Add starch solution to the boiling tube

  5. Mix and start a stopwatch, take samples every 30 seconds and add to iodine solution wells

  6. Repeat with different pH buffer solutions

  7. Control variables to make it a fair test
• Rate of reaction


  A measure of how much something changes over time, calculated as 1000/time taken
• Digestive enzymes


  • Carbohydrases (e.g. amylase)
  • Proteases
  • Lipases
• Carbohydrases


  Convert carbohydrates into simple sugars
• Amylase


  A carbohydrase that breaks down starch
• Amylase


  • Made in the salivary glands, pancreas, and small intestine