3. Gas Exchange Flashcards
(34 cards)
What happens to the s.a. and volume when the length of sides of a cuboidal cell increases?
- s.a. + vol ↑ exponentially
- vol ↑ at a ↑ rate than s.a.
- s.a. : vol ↓ exponentially
Calculate s.a. for spheres
4πr²
Calculate volume of sphere
4/3πr³
Environment around the cells of multicellular organisms
Tissue fluid.
What causes spiracles in an insect to open during movement?
↑ level of CO2
Suggest an advantage of spiracle movements to a terrestrial insect.
- helps conserve water
- ∵ spiracles x open continuously
- ∴ water x diffuse out continuously
State similarities between gas exchange in a plant leaf and in a terrestrial insect.
- diffusion in gas phase
- diffuse air thru pores in outer covering (opening & closing √ controlled)
- all living cells close to external air
- prevent water loss
State differences between gas exchange in a plant leaf and a terrestrial insect.
Insects:
1. create mass air flow vs X
2. ↓ sa : vol than plants
3. X interchange gases between resp & phots vs √
State one modification to reduce water loss that is shared by plants and insects.
- cuticle- waterproof
- ability to close openings of gas exchange system
Explain two reasons why plants growing on sand dunes need to have xerophytic features even though there is plentiful rainfall.
- rain rapidly drains out of reach of roots
- sand dunes- in windy situations- ↓ Ψ - ↑ Ψ gradient- ↑ water loss
Water flow over fish gills is one-way, whereas the flow of air in and out of the lungs is two-way.
Suggest why one-way flow is an advantage to fish.
- ↓ energy required
- ∵ flow x reversed (water is dense & diff. to move)
Explain 3 features of leaves of xerophytes to increase the uptake of water.
- deep extensive root system
– maximises water uptake (esp. during dry periods) - accumulation of solutes in the roots
– ↓ Ψ in root hair cell
– ↑ Ψ gradient from soil to root cells - some shallow roots
– absorb dew condensed on soil at night
+ immediately after rain
Features of specialised exchange surfaces
- ↑ s.a.
– ↑ rate of exchange - v. thin
– ↓ diffusion distance–>↑ rate of diffusion - selectively permeable
– √ selected materials to cross - movement of environmental medium
– maintains conc. gradient - transport system
– movement of internal medium (eg. blood) –> maintains diffusion gradient
Features of a single-celled organism
- ↓ diffusion pathway
– gases only have to pass plasma mem
–> ↓ distance to middle of cell - ↑ s.a. : vol
– vol small enough for s.a. to supply sufficient exchange of substances (eg. ants vs humans) - ↑ conc. gradient
– O2 continually used + CO2 produced in resp.
–> conc. gradient for each
Why do fish need exchange surfaces for gas exchange?
- water has ↓ dissolved O2 conc (1%)
- ↑ water needs to pass over fills–> enough O2
Advantage for having a large number of capillaries on the gills.
- ↑ s.a.
- ↓ diffusion pathway
- ↑ O2 diffuse at one time
What is the purpose of countercurrent flow?
Maintains a conc gradient down the entire length of the lamella–> ↑ O2 absorbed by blood
Explain the limitation of concurrent flow.
- water fully saturated w/ O2
- large conc gradient–> rapid diffusion into blood
- along lamaella- diffusion from water to blood down gradient
- until water & blood- equal saturation
- x conc gradient –> x diffusion
- max saturation of blood= only 50%🙁
How is the gas exchange system of fish adapted to increase surface area?
- each gill- 2 rows of gill lamella
- each lamella- many gill plates
- each gill plate- many capillaries
How is the gas exchange system of fish adapted to provide a short diffusion distance?
- lamella walls- 1 cell thick
- capillary walls- 1 cell thick
- blood close to surface of plate
How is the gas exchange system of fish adapted to maintain diffusion gradient?
- ventilation- continual flow of water
- countercurrent flow
- circulation of blood
Describe the process of inspiration.
active
- diaphragm contracts + flattens
- external intercostal muscles contract
- ribs up + out
- vol of thoracic cavity ↑
- pressure ↓
- air pushed into lungs down Pressure gradient
List the 4 measures of lung function
- tidal volume
- ventilation rate
- forced expiratory volume₁ (FEV₁)
- forced vital capacity (FVC)
Tidal vol
vol of each breath (~ 0.4 - 0.5dm³)
