bio ch10-ch21

• Pathogen


  Disease-causing microorganism
• Transmissible disease


  Disease in which the pathogen can be passed from one host to another
• How pathogens can be transmitted

  1. Direct contact (e.g. blood or body fluids)

  2. Indirectly (e.g. contaminated surfaces, food, in the air, animals)
• Body's defences to pathogens

  • Skin acts as a barrier
  • Hairs in nose trap pathogens and prevent entry
  • Mucus traps pathogens in trachea
  • Produced by goblet cells
  • Ciliated epithelial cells move mucus to mouth
  • Hydrochloric acid (HCl) in stomach destroys pathogens
  • Phagocytes engulf pathogens by phagocytosis
  • Lymphocytes produce antibodies
• Antigen


  Proteins (or other molecules) found on surfaces of cells and other pathogens, recognised by immune system as being 'non-self', each pathogen has own antigens with specific shapes
• Antibody


  Proteins that bind to antigens, specific antibodies have complementary shapes to specific antigens, causes direct destruction of pathogens or marks pathogens for destruction by phagocytes, transported around body in blood
• Methods to reduce disease

  • Clean water supply
  • Hygienic food preparation
  • Good personal hygiene
  • Waste disposal
  • Sewage treatment
• Active immunity


  Defence against a pathogen by producing antibodies specific to an antigen, gained after infection or vaccination
• How lymphocytes destroy pathogens

  1. Recognise antigens

  2. Make antibodies which destroy pathogens by: causing bacteria to stick together, label pathogen so it's easily recognisable by phagocytes, produce antitoxins, cause bacteria to burst
• How vaccines work


  Weakened pathogen (or their antigens) injected into body, antigens trigger immune response, lymphocytes produce antibodies, memory cells produced for long term immunity
• Why immune response is faster the second time a pathogen enters the body

  Memory cells made after initial infection or vaccination, produce antibodies much faster next time
• Vaccination


  Mass vaccination can prevent spread of pathogen into wider population, when a significant number of people have been vaccinated, it gives protection to those who do not have immunity (herd immunity)
• Passive immunity


  Short term defence against pathogens, antibodies acquired from another individual, memory cells are NOT produced, e.g. antibodies cross placenta from mother to fetus, antibodies transferred to infant in breast milk
• Importance of breastfeeding for development of passive immunity in infants
• Diarrhoea


  Loss of watery faeces
• How diarrhoea is treated

  Oral rehydration therapy - mixture of water and mineral salts, prevents dehydration
• Cholera


  Bacterial disease, bacteria produces toxin, toxin increases secretion of chloride ions into small intestine, leads to movement of water into gut by osmosis, causes diarrhoea, dehydration, loss of ions from blood
• How cholera is transmitted
• Gas exchange surfaces in humans

  • Large surface area, thin surface (short diffusion pathway), good blood supply (maintains steep concentration gradient), good ventilation with air (maintains steep concentration gradient), moist (gases can dissolve and diffuse faster)
• Ventilation


  Movement of air into and out of the lungs
• Alveoli adapted for gas exchange

  • Very large surface area, thin walls (single cell thick) - short diffusion distance, moist - allows gases to dissolve, good blood supply from capillaries - maintains steep concentration gradient, good ventilation - breathing maintains steep diffusion gradient
• Breathing in (inhalation)


  External intercostal muscles contract, ribs move up and out, diaphragm contracts and flattens, volume inside thorax increases, pressure decreases, air is sucked into the lungs
• Breathing out (exhalation)


  Internal intercostal muscles contract, ribs move down and in, diaphragm relaxes and become dome shaped, volume inside thorax decreases, pressure increases, air is forced out of the lungs
• Differences in composition between inspired and expired air

  • Oxygen (21% to 18%), Carbon dioxide (0.04% to 3%), Water vapour (variable to saturated), Nitrogen (78% to 78%), Temperature (variable to 37°C)
• How to test for carbon dioxide
• How exercise affects breathing rate and depth

  More exercise → increased rate of respiration → more carbon dioxide produced in muscles, carbon dioxide in blood increases, detected by receptors in the medulla (brain), causes increased breathing rate and depth
• How breathing system is protected from pathogens and particles

  • Mucus produced by goblet cells traps particles and pathogens, cilia on surface beat to move mucus, mucus moved up and out of lung, mucus swallowed and pathogens killed by stomach acid
• How energy is used in living organisms
• Investigating effect of temperature on respiration in yeast

  Add yeast to solution of glucose and water, leave at room temperature, place in water baths at different temperatures, seal test tube and count bubbles of CO2, plot graph of results
• Explanation of results of yeast respiration investigation
• Aerobic respiration


  Chemical reaction in cells, oxygen used to break down glucose to release energy
• Organelle where aerobic respiration occurs
• Word equation for aerobic respiration

  Glucose + Oxygen → Carbon dioxide + Water (+ energy)
• Symbol equation for aerobic respiration

  C6H12O6 + 6O2 → 6CO2 + 6H20
• Anaerobic respiration


  Chemical reaction in cells, glucose broken down to release energy, without using oxygen, releases less energy per molecule of glucose

  
• Advantage of using aerobic rather than anaerobic respiration
• Word equation for anaerobic respiration in yeast

  Glucose → Ethanol + Carbon dioxide
• Symbol equation for anaerobic respiration in yeast


  C6H12O6 → 2C2H5OH + 2CO2
• Word equation for anaerobic respiration in muscles

  Glucose → Lactic Acid
• Oxygen debt


  Build up of lactic acid in muscles and blood during exercise