3.3.2 Gas exchange Flashcards
Name 3 features of an efficient gas exchange surface
Large surface area; folded membranes in mitochondria
Short diffusion distance; walls of capillaries
Steep conc gradient; maintained by blood supply or ventilation eg alveoli
Why cant insects use their bodies as an exchange surface
They have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water
Name and describe the 3 main features of an insect’s gas transport system
Spiracles - holes on the bodys surface which may be opened or closed by a valve for gas or water exchange
Tracheae - large tubes extending through all body tissues supported by rings to prevent collapse
Tracheoles - smaller branches dividing off the tracheae
Explain the process of gas exchange in insects
Gases move in and out of the tracheae through the spiracles
A diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out
Contraction of muscles in the tracheae allows mass movement of air in and out
Why cant fish use their bodies as an exchange surface
They have waterproof, impermeable outer membrane and a small SA:V ratio
Name and describe the 2 main features of a fish’s gas transport system
Gills - located within the body, supported by arches, along which are multiple projections of gill filaments
Lamellae - at right angles to gill filaments, give an increased SA. Blood and water flow across them in opposite directions
Explain the process of gas exchange in fish
The fish opens its mouth to enable water to flow in, then closes its mouth to increase pressure
The water passes over the lamellae and the oxygen diffuses into the bloodstream
Waste carbon dioxide diffuses into the water and flows back out the gills
How does the countercurrent exchange system maximise oxygen absorbed by the fish
Maintains a steep concentration gradient, as water is always next to blood of a lower oxygen conc. Keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed
Name and describe 3 adaptations of a leaf that allow efficient gas exchange
Thin and flat to provide short diffusion pathway and large SA:V ratio
Many stomata allow gases to easily enter
Air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis
How do plants limit their water loss while still allowing gases to be exchanged
Stomata regulated by guard cells which allows them to open and close as needed
Most stay closed to prevent water lost while some open to let oxygen in
Describe the pathway taken by air as it enters the mammalian gaseous exchange system
Nasal cavity -> trachea -> bronchi -> bronchioles -> alveoli
Describe the function of the nasal cavity in the mammalian gaseous exchange system
A good blood supply warms and moistens the air entering the lungs.
Goblet cells in the membrane secrete mucus which traps dust and bacteria
Describe the trachea and its function in the mammalian gaseous exchange system
Wide tube supported by C shaped cartilage to keep the air passage open during pressure changes
Lined by ciliated epithelium cells which move mucus towards the throat to be swallowed preventing lung infections
Carries air to the bronchi
Describe the bronchi and their function in the mammalian gaseous exchange system
Like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells
However they are narrower and there are 2 of them, one for each lung
Allow passage of air into the bronchioles
Describe the bronchioles and their function in the mammalian gaseous exchange system
Narrower than the bronchi
Dont need to be kept open by cartilage, mostly muscle and elastic fibres so they can contract and relax easily during ventilation
Allow passage of air into the alveoli
