Gas exchange (6) Flashcards
(40 cards)
Why do multicellular organisms need specialised gas exchange surfaces?
their smaller SA:V ratio means the distance that needs to be crossed is larger + substances cannot easily enter the cells like in a single-celled organism
What are 3 features of efficient gas exchange?
1) large surface area e.g. folded membranes in mitochondria
2) thin/short distances e.g. wall of capillaries
3) stop concentration gradient, maintained by blood supply or ventilation e.g. alveoli
Why can’t insects use their bodies as an exchange surface?
- waterproof chitin exoskeleton
- small SA:V ratio in order to conserve water
Describe gas exchange in insects.
- gases move in and out of tracheae through spiracles
- diffusion gradient allows O2 to diffuse into body tissue whilst waste CO2 diffuses out
- contraction of muscles in the tracheae allows mass movement of air in and out
What are the 3 structures in an insect’s transport system?
1) spiracles
2) tracheae
3) tracheoles
What are spiracles?
holes on body’s surface which may be opened or closed by a valve for gas or water exchange
What are tracheae?
large tubes extending through all body tissues, supported by rings to prevent collapse
What are tracheoles?
smaller branches dividing off the tracheae
Why can’t fish use their bodies as an exchange surface?
- waterproof, impermeable outer membrane
- small SA:V ratio
What are the 2 features of fish gas transport systems?
gills
lamellae
What are gills and where are they found?
- located within the body
- supported by arches along which are multiple projections of gill filaments, which are stacked up in piles
What are lamellae?
at right angles to gill filaments
increase surface area
blood + water flow across them in opposite direction
What’s the term used to describe blood + water flowing in opposite directions?
counter-current exchange system
What is the process of gas exchange in fish?
(3 points)
1) fish opens mouth to enable water to flow in, then closes its mouth to increase pressure
2) water passes over lamellae and O2 diffuses into bloodstream
3) waste CO2 diffuses into water and flows back out of the gills
How does the counter-current exchange system maximise O2 absorbed?
maintains steep concentration gradient as water is always next to blood of a lower O2 concentration, which keeps rate of diffusion constant and enables 80% of available O2 to be absorbed
What are 3 adaptations of leaves which allow for efficient gas exchange?
1) think + flat
2) many stomata
3) air spaces in mesophyll
How does being thin + flat allow leaves to have efficient gas exchange?
provide short diffusion pathway and large SA:V ratio
How does having stomata allow leaves to have efficient gas exchange?
allow gases to easily enter
What are stomata?
minute pores on underside of leaf
How does having air spaces in mesophyll allow leaves to have efficient gas exchange?
allow gases to move around the leaf, facilitating photosynthesis
How do plants limit water loss?
- stomata regulated by guard cells which allows them to open and close as needed
- most stomata stay closed while some open to let O2 in
What is the order of the mammalian gaseous exchange system?
1) nasal cavity
2) trachea
3) bronchi
4) bronchioles
5) alveoli
What is the function of the nasal cavity?
- good blood supply warms and moistens air entering the lungs
- goblet cells in membrane secrete mucus which traps dust and bacteria
How do you calculate the pulmonary ventilation rate?
tidal volume x breathing rate
