gas exchange Flashcards
What are the adaptations for gas exchange of a
single-celled organism?
Thin, flat shape so
Large SA(:V)
Short diffusion pathway so it
Allows for rapid diffusion
Describe the adaptations for gas exchange relating to the
tracheal system of an insect.
Air moves through spiracles on the surface of the insect
Air moves through tracheae
Gas exchange at tracheoles directly to/from cells
Oxygen diffuses down conc. gradient to respiring cell
Carbon dioxide diffuses down conc. gradient from respiring cells
Adaptations: lots of thin, branching tracheoles → short diffusion pathway and SA(:V) →rapid diffusion
rhythmic abdominal movements increase the efficiency of gas exchange by increasing the amount of air/oxygen entering → maintains greater concentration gradient for diffusion
How do terrestrial insects limit water loss
Thick waxy cuticle
Increases diffusion distance → less evaporation
Spiracles can open and close
Open to allow oxygen in, close when water loss is too much
Adaptations of fish
-Counter current flow-maintains conc grad
-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
Describe the counter current flow system.
-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 (/gill plate) → equilibrium not met
-Maximising diffusion of oxygen
How do dicotyledonous plants show gas exchange
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 for gas exchange relating for leaves of dicotyledonous plants.
Lots of stomata (small pores) that are close together
Large surface area for gas exchange
Mesophyll cells have a large surface area
Rapid diffusion of gases
Thin
Short diffusion pathways
How do xerophytic plants limit water loss
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
The gross structure of human gas exchange system
Trachea—> splits into two bronchi—-> bronchioles—–>alveoli
gas exchange in 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 ventilation is necessary.
maintains a oxygen concentration gradient
Brings in air containing higher concentration of oxygen
Removes air with lower concentration of oxygen
Describe and explain the essential features of the alveolar
epithelium 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
Describe how the lungs are adapted for efficient/rapid gas
exchange
Many alveoli/capillaries
Large surface area → fast diffusion
Alveoli/capillary walls are thin
Short diffusion distance → fast diffusion
Ventilation/circulation
Maintains concentration gradient → fast diffusion
mechanism of inspiration.
External intercostal muscles contract, internal intercostal muscles relax
Moving ribcage up and out
Diaphragm muscles contract → flatten/move down diaphragm
Increasing volume in thoracic cavity / chest
Decreasing pressure in thoracic cavity
Atmospheric pressure higher than pressure in lungs
Air moves down pressure gradient into lungs
(Active process)
the mechanism of expiration.
Internal intercostal muscles contract, external intercostal muscles relax
Moving ribcage down and in
Diaphragm relaxes, moves upwards
Decreasing volume in thoracic cavity
Increasing pressure in thoracic cavity
Atmospheric pressure lower than pressure in lungs
Air moves down pressure gradient out of lungs
(Passive process)
