ORGANSISATION

• Cell


  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
• Cell organisation in large multicellular organisms

  1. Cells form tissues

  2. Tissues form organs

  3. Organs form organ systems
• Organ systems in large multicellular organisms

  • For exchanging and transporting materials
• Tissue


  A group of similar cells that work together to carry out a particular function
• Types of tissues in mammals

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Enzyme


  Biological catalyst produced by living things that increases the speed of chemical reactions without being changed or used up
• Living things have thousands of different chemical reactions going on inside them all the time
• Raising temperature


  Increases the rate of chemical reactions
• Catalyst


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


  • Large proteins made up of chains of amino acids folded into unique shapes
  • Need their active site to match the substrate for the reaction to be catalysed
• Active site


  Unique shape that fits onto the substance involved in a reaction
• Substrate


  The substance that an enzyme acts on
• Enzymes usually only catalyse one specific reaction
• Lock and key model


  Simplified model of how enzymes work
• Induced fit model


  More accurate model of how enzymes work, where the active site changes shape a little as the substrate binds to it
• Organs


  • Groups of different tissues that work together to perform a certain function
• Investigating the effect of pH on the rate of enzyme activity

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

  2. Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 35 °C

  3. Use a syringe to add 1 cm³ of amylase solution and 1 cm³ of a buffer solution with a pH of 5 to a boiling tube. Put the tube into the beaker of water and wait for five minutes

  4. Use a different syringe to add 5 cm³ of a starch solution to the boiling tube

  5. Immediately mix the contents of the boiling tube and start a stop clock

  6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch

  7. Repeat the whole experiment with buffer solutions of different pH values
• Tissues in the stomach

  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Rate of reaction


  A measure of how much something changes over time
• Organ systems


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

  • Glands (e.g. pancreas, salivary glands)
  • Stomach and small intestine
  • Liver
  • Small intestine
  • Large intestine
• If an experiment measures how much something changes over time, you calculate the rate of reaction by dividing the amount that it has changed by the time taken
• The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
• Organ systems work together to make entire organisms
• Optimum temperature


  Temperature where an enzyme is most active
• Enzymes


  Catalyse the breakdown of different food molecules
• Increasing temperature


  Increases the rate of an enzyme-catalysed reaction at first, but if it gets too hot it denatures the enzyme
• Enzymes used in digestion are produced by cells and then released into the gut to mix with food
• Enzyme production in the digestive system

  Produced by specialised cells in glands and in the gut lining
• Denatured


  When the bonds holding an enzyme together break, changing the shape of the active site so the substrate no longer fits
• Digestive enzymes


  Break down big molecules like starch, proteins and fats into smaller, soluble molecules that can pass through the walls of the digestive system
• Digestive enzymes


  • Different enzymes catalyse the breakdown of different food molecules
• Optimum pH


  pH at which an enzyme works best, as high or low pH can denature the enzyme
• Carbohydrases convert carbohydrates into simple sugars


  Amylase breaks down starch into maltose and other sugars
• Enzymes in the digestive system

  • Amylase in saliva
  • Pepsin in the stomach
  • Protease, amylase and lipase enzymes produced by the pancreas
• Pepsin is an enzyme that works best at pH 2 in the acidic conditions of the stomach
• Places where amylase is made

  • Salivary glands
  • Pancreas
  • Small intestine
• Bile


  Neutralises stomach acid and emulsifies fats