Gas Exchange Flashcards
Describe gas exchange in a single celled organism
Single celled organisms have a high sa:v so rate of diffusion is fast enough for sufficient gas exchange. So o2 for aerobic respiration and co2 diffuse in and out of the cell be simple diffusion
How is a fish adapted for gas exchange
- large sa : 4 gills and pairs of lamella
- short diffusion path
- excellent blood supply/transport system with a counter current system
- one way flow of water
Describe the counter current exchange system in fish
Blood flows through lamellae in one direction and water flows in the opposite direction. The o2 conc of water flowing towards blood is always higher than blood flowing towards the water. It allows for high saturation of o2 in the blood which maintains a steep o2 gradient and thus maximises o2 uptake
How does insects lacking haemoglobin affect the gas exchange system they have
Blood doesn’t transport o2 so have a gas exchange system that exchanges gases directly with the respiring tissues
Pathway of gas exchange in an insect
Air enters the exoskeleton via spiracles —> air travels along air filled tubes called trachea —> air diffuses into the surrounding tissues via fine branches (tracheoles)
Adaptations of insects to exchange gases
- highly branched (tracheoles) = inc sa = inc diff
- tracheole walls = 1 cell thick = decrease diff distance
- ventilate to maintain conc gradient
How might insects increase air flow
Rhythmic contractions of abdominal muscles + flight muscles causing an inc and decrease of abdominal pressure causing movement of air in and out of spiracles
Adaption of a leaf for gas exchange
- has a large sa = inc prob of diffusing gas colliding with the exchange surface)
- is thin so short diff path
- is permeable as has stomata
Role of stomata in gas exchange
Allow co2 to enter plant and o2 to be released by opening and closing (open in day for photosynthesis closed at night for respiration). Gases enter and exit by simple diffusion
Role of spongy mesophyll in gas exchange in plants
- creates a large sa
- airspaces permit lateral diffusion of gases allowing most cells to be in direct contact with air
- is moist which allows gases to move between gas and liquid phases
Adaption of xerophytes for preventing water loss during gas exchange
Water loss is unavoidable as stomata have to open for photosynthesis but xerophytes are adapted to arid environments by :
- rolled leaves - trap moist air to lengthen the diff gradient
- leaf hairs - reduce the disruption of diffusion shells and keep a long diffusion gradient
- sunken stomata - lengthen diff gradient
- no stomata on outside to decrease evaporation of water
How are the lungs adapted to efficient gas exchange
- many alveoli - large sa - inc rate of diff
- 1 cell thick (walls of alveoli and capillary) - short diff path - inc rate of diff
- good blood supply and movement of blood - inc conc gradient - inc rate of diffusion
- moist lining - gases dissolve - inc rate of diff into cells
- ventilation maintains conc gradient
- large differences in conc of metabolites between the alveoli + blood capillaries
How is the trachea adapted
- supported by C- shaped rings of cartilage to prevent the tube from collapsing during breathing
- inside trachea goblet cells secrete mucus to trap dust + other foreign material. Cilia waft + remove mucus + foreign material from respiratory system
Structure of alveoli
Is hollow, thin-walled sac that is surrounded by a dense network of capillaries
Mechanics of breathing at rest (inspiration)
External intercostals contract raising ribcage up and out, diaphragm also contracts and flattens this increases vol of thorax decreasing air pressure in cavity (less than atmosphere) which creates a pressure gradient between atmosphere and lungs so air rushes in
Mechanics of breathing at rest (expiration)
External intercostals relax so ribcage falls in and down, diaphragm relaxes (dome) decreasing vol of thorax increasing pressure in thoracic cavity (above atmosphere) causes pressure gradient and air rushes out
- is assisted by the elastic recoil of the lungs following the stretching of elastic fibres during the process of inspiration
Mechanics of breathing during exercise (inspiration)
Same just more forceful contractions
Mechanics of breathing during exercise (expiration)
Internal intercostals contract forcing ribcage down and in and abdominals contract pushing diaphragm in more domed position causing vol of thoracic cavity to decrease more significantly causing an increase in thoracic pressure aiding expiration
