exchange and transport

• Inspiration:

  1. external intercostal/diaphragm muscles contract
  2. ribcage moves up and out
  3. diaphragm flattens, increasing volume of thoracic cavity
  4. as volume in thoracic cavity increases pressure decreases
  5. Air moves down pressure gradient (from outside air, down trachea into lungs)
  6. active process
• Expiration:

  1. external intercostal/ diaphragm muscles relax
  2. ribcage moves down and in
  3. diaphragm relaxes.... volume of thoracic cavity decreases.... pressure increases
  4. Air moves down pressure gradient out of the lungs
  5. passive process
• alveoli adaptations:

  • thin walls- one cell thick... short diffusion pathway... faster rate of diffusion
  • large surface area- large number of alveoli... large surface area for gas exchange... faster rate of diffusion
  • steep concentration gradient-.....maintained by ventilation.... increases rate of diffusion
• Tidal volume- volume of air in each breath
• Ventilation rate- the number of breaths per minute
• Forced expiratory volume (FEV)- the maximum volume of air that can be breathed out in 1 second
• Forced vital capacity (FVC)- the maximum volume of air it is possible to breathe forcefully out of the lungs after deep breath in
• Fibrosis:

  • formation of scar tissue in the lungs.... from infection/exposure to substances e.g. asbestos
  • scar tissue is thicker/less elastic than normal lung tissue
  • lungs... less able to expand... cant hold as much air as normal
  • Tidal volume/FVC reduced
  • diffusion is slower across thicker membrane
  • faster ventilation rate ... to get enough oxygen
• Asthma:

  • smooth muscle lining bronchioles contracts/ large amount of mucus produced
  • constricts airways... airflow reduced
  • FEV reduced
• Emphysema:

  • caused by smoking/ air pollution
  • causes inflammation... attracts phagocytes to area.... phagocytes produce enzyme which breaks down elastin
  • loss of elastin means alveoli cant recoil/ expel air as well... remain trapped in alveoli
  • also destroy alveoli cell walls.... reducing the surface area.... rate of gaseous exchange decreases
  • increased ventilation rate
• TB

  • immune system builds a wall around the TB bacteria in lungs... forming small lumps... tuburcles
  • infected tissue within dies.. damaging gas exchange surface... decreasing tidal volume
  • causes fibrosis... further decreasing tidal volume
  • less air inhaled.... increased ventilation rate
• • Amylase (salivary glands/pancreas) catalyses hydrolysis of starch into maltose
  • hydrolysis of glycosidic bonds in starch
  • membrane-bound disaccharidases (enzymes attached to the cell membrane of epithelial cells) help break down disaccharides into monosaccharides (maltose->glucose)
  • monosaccharides can be transported across cell membranes via transporter proteins
• monoglycerides/fatty acids + bile salts= micelles
• Absorption/ transport of digested lipid molecules from the ileum into the lymph vessels:

  • Lipase hydrolyses ester bonds in triglycerides-> fatty acids/monoglycerides
  • Micelles contain bile salts + fatty acids/monoglycerides
  • Makes fatty acids/ monoglycerides more soluble in water
  • Bring/ release/ carry fatty acids/monoglycerides to cell/ lining of ileum
  • Fatty acids... absorbed by diffusion
  • Triglycerides reformed in cells
  • Vesicles move to cell membrane/exocytosis
• Examples of xerophytic adaptations:

  • Stomata sunk in pits- traps moist air. reducing the conc gradient of water between leaf/air... reducing rate of diffusion out
  • 'hairs' on epidermis- trap moist air around the stomata
  • Curled leaves with stomata inside- protecting them from wind (which increases the rate of diffusion)
  • reduced number of stomata
  • waxy, waterproof cuticles on leaves- reduce evaporation