3.2 - Gas exchange Flashcards
Describe how gas exchange works across the body surface of a single-celled organism
- simple diffusion
- flat cells/folds in cell surface membrane and/or flat body: increase SA (so SA:vol) + short diffusion distance
Describe how the tracheal system of an insect is specialised for gas exchange
- thin tracheole walls : short diffusion distance to cells
- highly branched: short diffusion distance to cells/large SA
- trachea tubes full of air: fast diffusion
- fluid in end of tracheoles moves out during exercise: faster diffusion through air to gas exchange surface
- body can be moved by muscles to move air: maintains diffusion gradient for O2/CO2
Describe how the gill system is specialised for gas exchange
- many lamellae/filaments: large SA
- thin: short diffusion pathway
Describe how the leaves of dicotyledonous plants are specialised for gas exchange
- stomata: open and close to allow gases in and out of leaf. turgid = open, flaccid = close
- mesophyll cells exchange surface = high SA
Describe the structural and functional compromises between efficient gas exchange and water loss in terrestrial insects and xerophytic plants
- gas exchange causes H2O loss
- adaptations: insects close spiracles using muscles if H2O loss too high
- waterproof waxy cuticle on body surface + 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 WP gradient
- sunken stomata: increases humidity and decreases WP
- thicker waxy cuticle: increases diffusion distance
- hairs on leaves: increases humidity and decreases WP gradient
- less stomata: less pores for H2O 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 SA: fast rate of diffusion
- 1 cell thick: short diffusion pathway
- capillary network: short diffusion pathway
Describe the mechanism of inspiration
- diaphragm contracts + flattens
- EIMs contract
- IIMs relax
- ribs move upwards
- vol increases + pressure decreases in thoracic cavity
- air flows into lungs down pressure gradient
Describe the mechanism of expiration
- diaphragm relaxes + moves up
- EIMs relax
- ribs move downwards
- IIMs contract
- vol decreases + 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
Define breathing rate
number of breaths/min
How can you determine breathing rate from a spirometer?
number of peaks/troughs per min
Define residual volume
volume of air always in lungs
Define inspiratory reserve volume
tidal volume exceeded to increase volume of air breathed in
Define expiratory reserve volume
additional volume of air that can be exhaled on top of tidal volume
Equation for pulmonary ventilation rate
tidal volume x breathing rate
Equation for residual volume
total lung capacity - vital capacity
