3.2 Gas exchange Flashcards
What are the adaptations of gas exchange surfaces shown by gas exchange…
Across the body surface of a single-celled organism
Thin, flat shape
- Large SA(:V)
- Short diffusion pathway/distance (all parts of cell are a small distance away from exchange surfaces)
For rapid diffusion e.g. oxygen / carbon dioxid
Describe the gas exchange across the tracheal system of an insect
- Air moves through spiracles (pores) on the surface of the insect
- Air moves through trachea
- Gas exchange at tracheoles directly to/from cells
- Oxygen diffuses down concentration gradient to respiring cell
- Carbon dioxide diffuses down concentration gradient from respiring cells
What are the adaptations of gas exchange surfaces shown by gas exchange…
In the tracheal system of an insect
Lots of thin, branching tracheoles -> short diffusion pathway and SA:V -> rapid diffusion
What is the counter current flow?
- Blood flows through lamellae and water flows over lamellae in opposite directions
- Always a higher concentration of oxygen in water than the blood it is near
- Hence, a concentration gradient of oxygen between the water and blood is maintained along the whole length of lamellae -> equilibrium not met
- Maximising diffusion of oxygen
Adaptations of gas exchange surfaces shown by gas exchange…
Across the gills of fish
- Counter current flow
- Each gill is made of lots of gill filaments (thin plates) which are covered in many lamellae -> gill filaments provide a large surface area, lamellae increase surface area even more
- Vast network of capillaries on lamellae -> remove oxygen to maintain a concentration gradient
- Thin/flattened epithelium -> shorter diffusion pathway between water and blood
What is the process of gas exchange in leaves?
- Carbon dioxide / oxygen diffuse through the stomata
- Stomata opened by guard cells
- Carbon dioxide / oxygen diffuse into mesophyll layer into air spaces
- Carbon dioxide / oxygen diffuse down concentration gradient
Adaptations of gas exchange surfaces shown by gas exchange…
By the leaves of dicotyledonous plants
- Lots of stomata (small pores) that are close together
- Large surface area for gas exchange / unimpaired movement of gases / gases do not have to pass through cells to reach mesophyll
- Interconnecting air space in mesophyll layers (exchange surface) - Gases come into contact with mesophyll cells
- Mesophyll cells have a large surface area - Rapid diffusion of gases
- Thin
- Short diffusion pathways
What are the structural and functional compromises between the opposing needs for efficient gas exchange and the limitation water loss shown by xerophytic plants?
Thick waxy cuticle - increases diffusion distance -> less evaporation
Stomata in pits/grooves - ‘trap’ water vapour -> water potential gradient decreased -> less evaporation
Rolled leaves - ‘trap’ water vapour -> water potential gradient decreased -> less evaporation
Spindles/needles - reduces surface area to volume ratio
Hairs - ‘trap’ water vapour -> water potential gradient decreased -> less evaporation
What are the structural and functional compromises between the opposing needs for efficient gas exchange and the limitation water loss shown by Terrestrial insects?
Thick waxy cuticle
- Increases diffusion distance→less evaporation
Spiracles can open and close
- Open to allow oxygen in, close when water loss too much
What are the structural and functional compromises between the opposing needs for efficient gas exchange and the limitation water loss shown by Terrestrial insects?
Thick waxy cuticle
- Increases diffusion distance→less evaporation
Spiracles can open and close
- Open to allow oxygen in, close when water loss too much
What is the structure of the human gas exchange system:
- Trachea
- Splits into two bronchi
- Each bronchus branches into smaller tubes called bronchioles
- Bronchioles end in air sacs called alveoli
How does gas exchange occur in the alveoli?
- Oxygen diffuses from alveoli
- Down its concentration gradient
- Across the alveolar epithelium
- Across the capillary endothelium
- Into the blood (in haemoglobin)
- Carbon dioxide diffuses from capillary
- Down its concentration gradient
- Across the capillary endothelium
- Across the alveolar epithelium
- Into the alveoli
Why is ventilation needed?
Maintains an oxygen concentration gradient
- Brings in air containing higher concentration of oxygen
- Removes air with lower concentration of oxygen
What are the essential features of the alveolar epithelium as a surface over which gas exchange takes place?
Squamous epithelium = thin/one cell thick
- Short diffusion pathway→fast diffusion
Large surface area to volume ratio
- Fast diffusion
Permeable
Good blood supply from network of capillaries
- Maintains concentration gradient
Elastic tissue allows it to recoil after expansion
Surfactant
How are the lungs adapted for efficient/rapid gas exchange?
Many alveoli/capillaries
- Large surface area→fast diffusion
Alveoli/capillary walls are thin / short distance between alveoli and blood
- Short diffusion distance→fast diffusion
Ventilation/circulation
- Maintains concentration gradient→fast diffusion
