Topic 3: Gas exchange Flashcards
What are the three features that all gas exchange surfaces have to increase the rate of exchange?
1.Large surface area
2.Short diffusion distance
3. Maintained concentration gradient
Describe the adaptations the alveoli have to increase the efficiency of gas exchange:
1.Alveoli are tiny air sacs, and there are 300 million in each human lung which creates a very large surface area for gas exchange (diffusion).
2.The alveolar epithelial cells are very thin, to minimise diffusion distance.
3.Each alveolus is surrounded by a network of capillaries to remove exchanged gases, and therefore maintains a concentration gradient.
State the adaptations the fish gills have to increase the efficiency of gas exchange:
1.To create a large surface area:volume for diffusion, there are many gill filaments covered in many gill lamellae.
2.There is a short diffusion distance due to a capillary network in every lamella and each gill lamella is very thin.
3.The concentration gradient is maintained by the countercurrent flow mechanism.
Use a diagram to help you to explain the importance of the countercurrent flow.
This is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.
This ensures that the diffusion gradient is maintained across the entire lamella.
Gas exchange in insects involves a tracheal system. What are the three key structures involved?
- Trachea
- Tracheoles
- Spiracles
State the adaptations the tracheal system has to increase the efficiency of gas exchange:
1.A large number of fine tracheoles - large surface area
2.The walls of the tracheoles are very thin and there is a short
distance between spiracles and tracheoles - a short diffusion
pathway
3.The use of oxygen and the production of carbon dioxide set up
steep diffusion gradients.
Describe how the tracheal system is involved in ventilation and how gases are exchanged.
Gas can exchange by diffusion, as when cells respire, they use up oxygen and produce carbon dioxide, creating a concentration gradient from the tracheoles to the atmosphere.
The second method of gas exchange is mass transport, in which an insect contract and relaxes its abdominal muscles to move gases en masse.
The final method is when the insect is in flight, where the muscle cells start to respire anaerobically to produce lactate. This lowers the water potential of the cells, and therefore water moves from the tracheoles into the cells by osmosis. This decreases the volume in the tracheoles and as a result, more air from the atmosphere is drawn in.
What are the three adaptations insects have to prevent water loss across their gas exchange surface?
- Insects have a small surface area to volume ratio where water can evaporate from.
2.Insects have a waterproof exoskeleton.
3.Spiracles, where gases enter and water can evaporate
from, can open and close to reduce water loss.
Describe gas exchange in plants.
The palisade mesophyll is the site of photosynthesis, where lots of oxygen is produced and carbon dioxide is used up. This creates a concentration gradient. Therefore, oxygen will travel through the air spaces in the spongy mesophyll and diffuse out of the stomata created by guard cells. Carbon dioxide will diffuse in through the stomata.
Describe the adaptations plants have to reduce water loss (including xerophytes).
To reduce water loss by evaporation, stomata close at night when photosynthesis wouldn’t be occurring.
Xerophytic plants are adapted to survive in environments with limited water.
Adaptations include sunken stomata, fewer stomata, rolled leaves and tiny hairs around the stomata. Waxy future, needle-like leaves to reduce SA sp less evaporation. Deep root system to reach more water.
