EXCHANGE SYSTEMS

• how do single celled organisms do gas exchange

  diffusion as no need for gas ex system
• what's the gas exchange system for fish

  counter current system in gills
• explain counter current system

  • water containing 02 enters mouth and passes through gills
  • blood flows over lamellae In one direction and water flows over in the opposite direction
  • This maintains a large conc gradient between water and blood
  • water always has a higher 02 conc than blood to ensure that more 02 diffuses into the blood
  • diffusion happens across whole gill length
• How is the gill adapted for efficient gas exchange

  • made up of lots thin gill filaments
  • covered in lamellae which have lots of blood capillaries

  LOTS OF THEM= LARGE SA for gas exchange

  THIN=short diffusion pathway

  LOTS OF CAPILLARIES= Maintains diffusion gradient
• How do fish let water in for gas exchange

  1. mouth opens
  2. floor of mouth lowered
  3. water enters due to decreased pressure
  4. mouth closes
  5. floor raised, inc pressure
  6. High pressure pushes water over gills
• Structure of the mammalian breathing system enables efficient uptake of oxygen into the blood

  1. Alveoli provide a large surface area

  2. Walls of alveoli thin to provide a short diffusion pathway

  3. Walls of capillary thin / close to alveoli provides a short diffusion pathway

  4. Walls of capillaries / alveoli have flattened cells

  5. Cell membrane permeable to gases

  6. Many blood capillaries provide a large surface area

  7. Intercostal / diaphragm muscles to ventilate lungs to maintain a diffusion / concentration gradient

  8. Wide trachea and bronchioles for efficient flow of air

  9. Cartilage rings keep airways open
• Explain how young fish get enough oxygen to their cells without having gills

  • diffusion across body surface
  • short diffusion pathway
•  Suggest one advantage to a fish of this one-way flow of water over its gills rather than having 2 way flow

  less energy needed
• Water containing dissolved oxygen flows over the gill in the opposite direction to the blood flow inside. Explain why this arrangement is important for efficient oxygen uptake.

  maintains concentration gradient to ensure diffusion happens over full length of gill
• Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.

   1. Tracheoles have thin walls so short diffusion distance to cells;

  2. Highly branched / large number of tracheoles so large surface area

  3. Tracheae provide tubes full of air so fast diffusion

  4. Fluid in the end of the tracheoles moves out during exercise so larger surface area

  6. Body can be moved by muscles to move air (RHYMIC ABDONIMAL MOVEMENT) so maintains concentration gradient for carbon dioxide;
• label F and G

  F= filament

  G=lamellae

  
• The pieces of leaf tissue examined were very thin.

  Explain why this was important.

  • single layer of cells
  • Allows light to pass through
• XEROPHYTIC FEATURES

  1. Hairs on leaves = trap water vapour to reduce water potential gradient

  2. Stomata in pits/grooves =trap water vapour and reduce water potential gradient

  3. Thick waxy cuticle = increases diffusion distance and reduce evaporation as impermeable to water

  5.      Rolled/folded/curled leaves= trap water vapour to decrease water potential gradient

  6.   Spines/needles = reduces surface area to volume ratio

  7. Reduced number of stomata=less places for water to escape
• Suggest reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration.

  1. Water used for support/turgidity

  2. Water used in photosynthesis;

  3.      Water used in hydrolysis;

  4.      Water produced during respiration;
• BREATHING IN

  1. external intercostal and diagram muscles contract
  2. ribcage moves up and out
  3. diaphragm flattens
  4. vol of thoriac cavity inc + lung pressure decreases
  5. air flows down trachea due to pressure gradient
• BREATHING OUT

  • external intercostal and diaphragm muscles relax
  • ribcage moves down and in
  • diagram curves
  • vol of thoriac cavity decreases
  • lung pressure inc
  • air forced down pressure gradient and out of the lungs
• ALVEOLI

  • large no. of them
  • surrounded by network of capillaries
  • thin+flat
  • steep conc gradient of co2 and o2
• In alveoli, oxygen diffuses across aveolar epithelium then capillary endothelium and into haemoglobin down conc gradient
• oxygen from air moves down trachea, into bronchi/bronchioles and into alveoli all down the pressure gradient
• TIDAL VOLUME= Vol of air in each breath
• VENTILATION RATE= Breaths per minute
• FEV1= Max vol of air that can be breathed out per second
• FVC= Max volume of air possible to breathe forcefully out after breathing in
• ASTHMA

  • Airways become inflamed and irritated due to irritants eg.pollen or disy
  • Smooth muscles lining bronchioles contract producing mucus
  • causes constriction of airways meaning airflow is reduced therefore reduced FEV1
  • symptoms ; wheezing, tight chest, shortness of breath
  • Can be relieved using drugs that relax the bronchiole muscles such as inhalers
• FIBROSIS

  • Formation of scar tissue making lungs thicker and less elastic
  • Lungs are less able to expand so reduces tidal volume and FVC
  • Longer diffusion pathway = reduction in diffusion
  • have a faster ventilation rate to get In enough air to oxygenate blood
  • symptoms; shortness of breath, dry cough, chest pain, fatigue, weakness
• EMPHYSEMA

  • Lung disease caused by smoking or long term exposure to pollution
  • Foreign particles become trapped in alveoli causing inflammation which attracts phagocytes which produce enzymes that destroy the elastin in alveoli walls
  • loss in elastin= alveoli can't recoil to expel air meaning it gets trapped leading to destruction of alveoli walls
  • symptoms; shortness of breath, wheezing, inc ventilation rate