B1-1&2

• Cells


  The basic building blocks that make up all living organisms
• Specialised cells


  Cells that carry out a particular function
• Differentiation


  The process by which cells become specialised for a particular job
• Cell organisation in large multicellular organisms

  1. Cells form tissues

  2. Tissues form organs

  3. Organs form organ systems
• Large multicellular organisms 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
• Organ


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

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Organ system


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

  • Glands (pancreas, salivary glands)
  • Stomach
  • Small intestine
  • Liver
  • Large intestine
• Organ systems work together to make entire organisms
• Living things have thousands of different chemical reactions going on inside them all the time
• Catalyst


  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Enzyme


  A biological catalyst produced by living things
• Enzymes


  • They reduce the need for high temperatures to speed up useful chemical reactions
  • They only speed up the useful chemical reactions in the body
• Active site


  The unique shape of an enzyme that fits the substance involved in a reaction
• Substrate


  The substance that an enzyme acts on
• Denatured


  When the shape of an enzyme's active site is changed, so the substrate no longer fits
• Optimum temperature


  The temperature where an enzyme is most active
• Optimum pH


  The pH where an enzyme works best
• Pepsin is an enzyme used to break down proteins in the stomach, it works best at pH 2
• Investigating the effect of pH on amylase activity

  1. Add amylase and buffer solution to a boiling tube

  2. Add starch solution and start timer

  3. Take samples every 30 seconds and test with iodine

  4. Repeat with different pH buffers
• Rate of reaction


  A measure of how much something changes over time
• Digestive enzymes are produced by cells and released into the gut to mix with food
• Carbohydrases


  Enzymes that convert carbohydrates into simple sugars
• Carbohydrases


  • Amylase
• Proteases


  Enzymes that convert proteins into amino acids
• Lipases


  Enzymes that convert lipids into glycerol and fatty acids
• The body makes good use of the smaller molecules like sugars, amino acids and glycerol produced by digestive enzymes
• Bile


  A substance produced in the liver that neutralises stomach acid and emulsifies fats
• Lipids


  Fats and oils
• Lipases convert lipids


  Lipids into glycerol and fatty acids
• Amylase


  Breaks down starch
• Places where amylase is made

  • Salivary glands
  • Pancreas
  • Small intestine
• Places where proteases are made

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Places where lipases are made

  • Pancreas
  • Small intestine
• The body makes good use of the products of digestion. They can be used to make new carbohydrates, proteins and lipids. Some of the glucose (a sugar) that's made is used in respiration
• Bile


  Produced in the liver, stored in the gall bladder, released into the small intestine
• Role of bile


  • Neutralises stomach acid to make conditions alkaline for enzymes in the small intestine
  • Emulsifies fats to increase surface area for lipase enzyme
• Amylase, protease and lipase are examples of enzymes, and you should know the reactions that they catalyse