B3.1 - gas exchange in animals (6e) Flashcards
What is gas exchange?
Gas exchange is the process by which oxygen diffuses into the cells of an organism and carbon dioxide diffuses out.
Why do the challenges of gas exchange get bigger as organisms increase in size?
- Surface area to volume ratio decreases with increasing size.
- Distance from the centre of an organism to its exterior increases.
What are the 4 properties of gas exchange surfaces?
- Permeable to oxygen and carbon dioxide
- Thin tissue layer
- Large surface area
- Moist
How does an exchange surface being permeable to oxygen and carbon dioxide contribute to gas exchange?
Allows oxygen and carbon dioxide to move through the cell membranes of the gas exchange surface by simple diffusion.
How does having a thin tissue layer contribute to gas exchange?
To reduce the diffusion distance:
- alveoli (in lungs)
- lamellae (in gills)
- capillaries
How does having a large surface area contribute to gas exchange?
Millions of clusters of alveoli / gill filaments to increase the rate of diffusion.
How does being most contribute to gas exchange?
Allows the gases to dissolve, in order to be exchanged.
Why are concentration gradients maintained?
Concentration gradients are maintained to allow gas exchange both into and out of the blood to occur by diffusion.
What are 3 ways that concentration gradients are maintained?
- Ventilation
- Dense network of blood vessels
- Continuous blood flow
How does ventilation maintain a concentration gradient?
- Inhalation brings fresh air / water with high concentration of oxygen to the exchange surface.
- Exhalation gets ride of stale air / water with high concentrations of carbon dioxide
e.g) mammals ventilate lungs with air
e.g) fish ventilate gills with water
How does a dense network of blood vessels maintain a concentration gradient?
Highly vascularised lung tissue means adjacent capillaries enclose each alveolus for efficient gas exchange.
How does a continuous blood flow maintain a concentration gradient?
- transporting carbon dioxide to the exchange site (alveoli / lamellae), maintaining a higher concentration than in the air / water
- removing oxygen from the exchange site, maintaining a lower concentration than in from the air / water
What are the adaptations of lungs and gills for gas exchange? (BLTVM)
B - rich supply of capillaries, moving blood.
- Maintains a high concentration of carbon dioxide and a low concentration of oxygen in the capillaries surrounding the alveoli / lamellae for efficient gas exchange.
L - large surface area.
- Many spherical-shaped alveoli / feather-shaped gill filaments means more efficient diffusion.
T - thin walls.
- Alveoli, lamellae and capillaries are one cell thick, providing short diffusion distances for rapid diffusion.
V -ventilation.
- Maintains concentration gradients of oxygen and carbon dioxide between air in lungs / water in gills, and blood flowing in adjacent capillaries.
M - moist lining of alveoli.
- Dissolves the gases to allow exchange to occur.
What are the 6 adaptations of mammalian lungs for gas exchange?
- Dense capillary network
- Continuous blood flow
- Ventilation
- Branched network of bronchioles
- Thin walls due to type I pneumocytes
- Moist lining containing surfectant
How does a dense capillary network aid gas exchange in mammals?
The highly vascularized lung tissue means the adjacent capillaries enclose each alveolus for efficient gas exchange.
How does a continuous blood flow aid gas exchange in mammals?
This maintains concentration gradients by:
- transporting carbon dioxide to the exchange site (alveoli / lamellae), maintaining a higher concentration than in the air / water
- removing oxygen from the exchange site, maintaining a lower concentration than in from the air / water
How does ventilation aid gas exchange in mammals?
- Inhalation brings fresh air / water with high concentration of oxygen to the exchange surface.
- Exhalation gets ride of stale air / water with high concentrations of carbon dioxide
How does a branched network of bronchioles aid gas exchange in mammals?
This allows each cluster of alveoli to be connected into the trachea, for access to inspired and expired air.
- Thus, increasing the surface area of the exchange surface.
How does a thin walls due to type I pneumocytes aid gas exchange in mammals?
- Extremely thin alveolar cells
- Adapted to carry out gas exchange by providing a short diffusion distance
How does a moist lining containing surfectant aid gas exchange in mammals?
Secreted by type II surfectant prevent the sides of the alveolus adhering to each other by reducing surface tension.
