Gas Exchange Flashcards
What is the structure of gas exchange in insects?
They have openings called spiracles which connect to the trachea which join to tracheoles which join to cells.
Explain how insects carry out gas exchange along a diffusion gradient
Along a diffusion gradient - oxygen is used up in the cells so it’s concentration lowers, oxygen moves in from air to cells (high -> low)
CO2 gets produced in cells so it’s concentration increases, moves down its concentration gradient into the air.
Explain how insects carry out gas exchange by mass transport
They contract their muscles which enable mass movements of air in and out
Explain how insects carry out gas exchange using tracheoles
- muscle cells respire and produce lactate
- lowers water potential of cells
- water moves into the cells by osmosis from the tracheoles
- volume of water in tracheoles decreases
- this draws more air in
Describe the structure of fish gills
They are made of gill filaments
And gill lamellae at right angles to the filaments
How is water passed along the gills?
Water is taken in through the mouth and over the gills
The flow of water and the flow of blood are in opposite directions
Describe the difference between parallel flow and countercurrent flow
Parallel - if water and blood flowed the same way eventually the concentration would become the same and there would be no net movement
Countercurrent - there is always a higher concentration of oxygen in the water than in the blood so a diffusion gradient is always maintained
What are the adaptations plants have for gas exchange?
Many stomata
Air spaces that are interconnected
Large surface area
How do plants limit water loss?
Thick cuticle (waterproof)
Rolled up leaves so that the stomata are not exposed to air
Reduced surface area : volume ratio
What is the structure of the human gas exchange system?
Lungs Trachea Bronchi Bronchioles Alveoli
Explain the mechanism of inspiration
Inhalation - external intercostal muscles contract Internal intercostal muscles relax Ribs go up and out Diaphragm contracts and flattens Volume of thorax increases Pressure decreases Pressure in air > pressure in lungs Air moves in
Explain the mechanism of expiration
expiration
- external intercostal muscles relax
- internal intercostal muscles contract
- ribs move down and in
- diaphragm relaxes and curves up
- volume in thorax decreases
- pressure increases
- pressure in lungs > pressure atmospheric
- air is forced out
What is the equation for pulmonary ventilation
PV = tidal volume x ventilation rate
Tidal volume = volume breathed out in one breath
Ventilation rate = number of breaths per minute
pv = volume of air breathed in a minute
How are alveoli adapted for gas exchange?
A lot of them = increased surface area
One cell thick = short diffusion distance
Ventilated = maintains diffusion gradient
How does O2 move from alveoli to capillaries?
They pass through the alveolar epithelium and across the capillaries endothelium
How does CO2 move from the capillaries to the alveoli?
Pass through the capillary endothelium and through the alveolar epithelium
Explain how asthma reduces the rate of diffusion
Allergens trigger an immune response Histamines cause bronchoconstriction Constrictions reduce tidal volume Air in alveoli gets replaced slowly Tidal volume decreases Rate of diffusion decreases
How does tuberculosis reduce diffusion
Scar tissue is formed when bacterial cells trigger an immune response
This reduces the surface area of the alveoli so diffusion is greatly reduced
How does emphysema reduce diffusion
Tar stimulates the production of protease enzymes which digest elastin
Alveoli can no longer expand and recoil
Reduces tidal volume
Less oxygen diffuses into the blood
