Organisation

• Cell Organisation

  How cells become specialised for a particular job
• Differentiation

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

  • Unspecialised cell
  • Specialised cell
• Differentiation occurs during the development of a multicellular organism
• 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
• Organ

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

  • Muscular tissue that moves the stomach wall
  • Glands that make digestive juices
  • Epithelial tissue that covers the outside and inside of the stomach
• Organ system

  A group of organs working together to perform a particular function
• Organ systems work together to make entire organisms
• Enzyme

  A catalyst produced by living things that increases the speed of a chemical reaction without being changed or used up in the reaction
• Enzymes

  • They are large proteins made up of chains of amino acids folded into unique shapes
  • They have an active site with a unique shape that fits onto the substance involved in a reaction
• Induced fit model of enzyme action

  The active site changes shape a little as the substrate binds to it to get a tighter fit
• As temperature increases

  The rate of enzyme-catalysed reactions increases at first
• As temperature increases further

  The bonds holding the enzyme together break, changing the shape of the active site so the substrate can no longer fit
• Optimum temperature

  The temperature at which an enzyme works best
• Optimum pH

  The pH at which an enzyme works best
• Enzymes catalyse just one specific reaction
• The optimum temperature for most human enzymes is around normal body temperature
• Stomach enzymes work best at low pH, but 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 each well

  2. Heat water in a beaker and use a thermometer to keep the temperature constant

  3. Add enzyme and buffer solution to a test tube and wait 5 minutes

  4. Add starch solution and start a stopwatch

  5. Take samples every 30 seconds and test for presence of starch

  6. Repeat with buffer solutions of different pH
• Rate of reaction

  A measure of how much something changes over time, calculated by dividing the amount of change by the time taken
• Enzymes in the digestive system are produced by specialised cells in glands and tissues
• Digestive enzymes

  • Carbohydrases
  • Proteases
  • Lipases
• Bile

  Produced in the liver, stored in the gall bladder, and released into the small intestine to neutralise stomach acid and emulsify fats
• The whole digestive system is actually a big hole that goes right through the body
• Reducing sugars

  Sugars that can be oxidised by Benedict's solution
• Benedict's test for reducing sugars

  1. Prepare food sample

  2. Add Benedict's solution

  3. Heat in water bath

  4. Observe colour change
• Starch

  Complex carbohydrate found in foods like potatoes, pasta, rice
• Iodine test for starch

  1. Prepare food sample

  2. Add iodine solution

  3. Observe colour change
• Proteins

  Large molecules made up of amino acids
• Biuret test for proteins

  1. Add biuret solution to food sample

  2. Observe colour change
• Lipids

  Fats and oils found in foods like olive oil, margarine, milk
• Sudan III test for lipids

  1. Add Sudan III stain to food sample

  2. Observe separation into layers
• Safety precautions are important when conducting food tests
• The lungs are located in the thorax, protected by the ribcage
• Pathway of air through the lungs

  1. Trachea

  2. Bronchi

  3. Bronchioles

  4. Alveoli
• Alveoli

  Small air sacs in the lungs where gas exchange occurs
• Blood flows through the alveoli

  Oxygen diffuses into the blood and carbon dioxide diffuses out
• Breathing rate

  Number of breaths per minute