Paper 1: Gas exchange Flashcards
SA: Vol
Larger organisms have a smaller SA: volume ratio
factors that increase rate of gas exchange [3]:
- High surface area
- Short diffusion distance
- High conc gradient
what does a high SA: Vol mean? [3]:
- Organism loses more heat pre gram of body
- means faster rate of respiration
- so more o2 needed to maintain a constant body temp
Gas exchange- insects [4]:
- Air enters thru spiracles
- O2 diffuses down conc gradient along trachea
- Trachea are closely surrounded by cells
- O2 diffuses into these cells
Water loss- insects [3]:
- Ventilation keeps a high Ψ gradient
- Body covered in waxy cuticle which prevents evaporation
- Can close spiracles to prevent water loss
Fish adaptations- SA [2]:
- Filaments & lamellae in gills have large SA
- increases efficiency of diffusion
Fish adaptations– Shor diffusion pathway [2]:
- Lamellae/ filaments have a thin epithelium
- Creates a short diffusion pathway
Fish adaptations- Countercurrent [3]:
- Maintains steep conc gradient
- water is always next to blood with a lower conc of o2
- Circulation of blood & ventilation always replacing blood that’s been saturated w/ o2
counter current flow =
blood with low o2 flows in opposite direction than water with high o2
Plant adaptations for gas exchange- mesophyll [3]:
- Is spongy so has gaps in it
- increases SA
- More gases can interact w/ surface
Stomata
Gap between two guard cells
How do dicotyledenous plants prevent water loss? [2]:
- Plant cells become turgid when they lose water
- Flaccid guard cells close stomata to prevent water loss
Adaptations of xerophytic plants [5]:
- Curled leaf
- sunken stomata
- Hairs on epidermis
- Thick waxy cuticle
- fewer stomata
why do xerophytic plants have curled leaves? [2]:
- Causes water vapour to build up
- This decreases the water diffusion gradient
why do xerophytic plants have sunken stomata? [2]:
- Causes water vapour to build up
- This decreases the water diffusion gradient
why do xerophytic plants have hairs on the epidermis? [2]:
- Causes water vapour to build up
- This decreases the water diffusion gradient
why do xerophytic plants have a thick waxy cuticle?
Reduces evaporation
why do xerophytic plants have fewer stomata?
Lest water lost in gas exchange
What human adaptation causes a large SA for gas exchange? [2]:
- Bronchioles attached to folded sacks called alveoli
- there are lots of em
How do humans have a conc gradient for gas exchange?
Alveoli surrounded by many capillaries
How do humans have a short diffusion pathway for gas exchange?
Alveoli has thin epithelium thats 1 cell thick
Ventilation in humans
Brings in air with high o2 and replaces low conc air
circulation in humans
replaces blood thats high in o2 w/ blood that’s low in o2
Tidal volume =
The volume of air breathed in or out per breath, at rest
breathing/ ventilation rate =
No. breaths per min
Pulmonary ventilation [definition]:
Total vol of air breathed
Pulmonary ventilation =
tidal volume x breathing/ ventilation rate
How does exercise affect tidal volume?
Increases ( deeper breaths)
How does exercise affect breathing rate?
Increases (faster breaths)
How does exercise affect Pulmonary ventilation?
Increases
How does exercise affect O2 consumption?
Increases (more respiration)
Inspiration [5]:
- Diaphragm contacts, flattening
- External intercostal muscles contract, pushing ribcage up & out
- Increases vol of thorax so pressure decreases
- below atmospheric pressure
- Air moves in from high to low
what happens in forced expiration? [2]:
- Internal intercostal muscles contract
- Pulls ribcage down & in more & faster than norm
