3.2 - Gas exchange Flashcards
Describe how gas exchange works across the body surface of a single-celled organism
- no specialised gas exchange surfaces/transport systems, reliance on diffusion
- typically flat cells or folds in their cell surface membrane to increase surface area (and therefore SA:vol ratio) and ensure short diffusion distance
- small multi-cellular organisms without specialised gas exchange surfaces also typically have flat body shapes for the same reasons
Describe how the tracheal system of an insect is specialised for gas exchange
- thin tracheole walls so short diffusion distance to cells
- highly branched so short diffusion distance to cells/large SA
- trachea provide tubes full of air so fast diffusion
- fluid in the end of tracheoles moves out during exercise so faster diffusion through air to gas exchange surface
- body can be moved by muscles to move air so maintains diffusion gradient for oxygen/carbon dioxide
Describe how the gill system is specialised for gas exchange
- many lamellae/filaments so large SA
- thin so short diffusion pathway
Describe how the leaves of dicotyledonous plants are specialised for gas exchange
- stomata = small pores open and close to allow gases in and out of leaf. (controlled by guard cells)
- turgid (full of water) = stomata open
- flaccid = stomata close
- exchange surface = mesophyll cells, which have high SA
Describe the structural and functional compromises between efficient gas exchange and water loss in terrestrial insects and xerophytic plants
- gas exchange causes water loss
- adaptations: insects close spiracles using muscles if water loss is too high
- waterproof waxy cuticle on body surface and tiny hairs around spiracles reduce evaporation
- dehydrated plants = stomata close
Draw a diagram of the gross structure of the human gas exchange system
Alveoli
Bronchioles
Bronchi
Trachea
Lungs
Name and describe the adaptations of xerophytic plants
- curled leaves = increases humidity and decreases water potential gradient
- sunken stomata = increases humidity and decreases water potential
- thicker waxy cuticle = increased diffusion distance
- hairs on leaves = increases humidity and decreases water potential gradient
- less stomata = less pores for water loss
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish
- water and blood flow in opposite directions
- maintains O2 diffusion gradient
- blood always passing water with higher oxygen concentration
- along whole length of lamella
Describe adaptations of the alveolar epithelium for efficient gas exchange
- large total SA
- 1 cell thick so short diffusion pathway
- surrounded by capillary network
Describe the mechanism of inhalation
- diaphragm contracts
- external intercostal muscles contract
- internal intercostal muscles relax
- volume increases and pressure decreases in thoracic cavity
- air flows into lungs down pressure gradient
Describe the mechanism of exhalation
- diaphragm relaxes
- external intercostal muscles relax
Internal intercostal muscles contract - volume decreases and pressure increases in thoracic cavity
- air flows out of lungs down pressure gradient
Describe the pathway taken by an oxygen molecule from an alveolus to the blood
- across alveolar epithelium
- to endothelium of capillary
Why do gills stick together when a fish is out of water?
lamella held apart by water flow so when there is none they stick together so fish cannot survive long
Define vital capacity
max volume of air that can be inhaled/exhaled in a single breath
varies based on age, height, gender etc.
Define tidal volume
volume of air breathed in and out at each breath at rest
