3.2 Gas Exchange Flashcards
(14 cards)
How are single-celled organisms adapted for gas exchange?
• Thin, flat shape
• So large surface area to volume ratio and short diffusion distance to cells
How is an insects tracheal system adapted for gas exchange?
• Spiracles can open to allow gas exchange
• Air filled trachea so fast diffusion
• Tracheoles have thin walls so short diffusion distance to cells
• Tracheoles highly branched so large surface area and short diffusion distance to cells
• Contraction of abdominal muscles maintains a steep concentration gradient for diffusion
How are insects adapted to limit water loss?
• Thick waxy cuticle/exoskeleton, increasing diffusion distance so less water loss by evaporation
• Spiracles can close so less water loss by evaporation
• Hairs around spiracles to trap water vapour, reducing water potential gradient so less water loss by evaporation
How are fish gills adapted for gas exchange?
• Many gill filaments with many lamellae so large surface area
• Thin lamellae wall / epithelium so short diffusion distance to blood
• Many capillaries, maintaining a steep concentration gradient
What is the counter current flow system?
• Blood and water move in opposite directions
• So oxygen concentration always higher in water
• So maintains a steep concentration gradient of oxygen between water and blood
• For diffusion along entire length of lamellae
How are leaves of dicotyledonous plants adapted for gas exchange?
• Many stomata so large surface area for gas exchange
• Spongey mesophyll contains air spaces so large surface area for gas exchange
• Thin so short diffusion distance
How are xerophytic plants adapted to limit water loss?
• Thick waxy cuticle, increasing diffusion distance so less water loss by evaporation
• Sunken stomata in pots / hairs / rolled leaves to trap water vapour, reducing water potential gradient so less water loss by evaporation
• Spines to reduce surface area it volume ratio
How is does gas exchange occur in the lungs?
• Oxygen diffuses down trachea, bronchi, bronchioles, alveoli down concentration gradient
• Across alveolar epithelium and capillary endothelium
How is the alveolar epithelium adapted for gas exchange?
• Flattened cells / one cell thin so short diffusion distance
• Folded so large surface area
• Moist so gases can dissolve for diffusion
• Good blood supply from capillaries so maintains steep concentration gradient
Why is ventilation important?
• Brings in air containing higher concentration of oxygen and removes air with lower concentration of oxygen
• Maintaining a steep concentration gradient
Inspiration
• Diaphragm contracts and flattens
• External intercostal muscles contract (and internal intercostal muscles relax), ribs pulled up and out
• Increasing volume and decreasing pressure of thoracic cavity
• Air moves into lungs down pressure gradient
Expiration
• Diaphragm relaxes and domes
• External intercostal muscles relax (and internal intercostal muscles contract), ribs pulled down and in
• Decreasing volume and increasing pressure of thoracic cavity
• Air moves out lungs down pressure gradient
Why is expiration normally passive at rest?
• Internal intercostal muscles do not normally need to contract
• Expiration aided by elastic recoil in alveoli
How can lung diseases affect gas exchange?
• Thickened alveolar tissue, increasing diffusion distance
• Alveolar wall breakdown, reducing surface area
• Reduced lung elasticity so lungs expand/recoil less, reducing concentration gradient
