3. Gas Exchange Flashcards
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)
Ventilation rate
no. of breaths per minute (~15 at rest)
Forced expiratory volume₁
- max vol of air
- breathed out
- in 1 sec
Forced vital capacity (FVC)
- max vol
- breathe forcefully out
- after deep breath in
- max vol of lung
Residual volume
- vol remaining in lungs
- after max forceful expiration
- x expired ∵ keeps alveoli open at all times
Inspiratory reserve vol
- vol forcefully inhaled
- after normal tidal vol
(deep breathing)
Expiratory reserve vol
- additional vol to be exhaled
- after normal exhalation
Functional residual capacity
vol at the end of passive expiration
Formula for minute ventilation rate (VE)/ pulmonary ventilation
tidal volume x ventilation rate
Pulmonary fibrosis is a lung disease that causes the epithelium of the lungs to become irreversibly thickened. It also leads to reduced elasticity of the lungs.
One symptom of the disease is shortness of breath, especially when exercising. Suggest why this ymptom arises.
- thickened epithelium of alveoli- ↑ diffusion distance
- ↑** air space** in lung occupied by fibrous tissue- ↓ O2 each breath
- loss of elasticity- hard to ventilate + maintain diffusion gradient
- breathless- attempt to compensate by breathing faster
List 5 main risk factors for lung diseases.
- smoking
- air pollution
- genetic make-up
- infections
- occupation
