Topic 4.2 Gas exchange Flashcards
Why can small organisms rely on diffusion alone for gas exchange?
- diffusion distances from the outside to the innermost areas are very small
- large SA:V so large areas for substances to diffuse into
- metabolic demands are low- organisms don’t regulate their own body temperature and cells don’t use much oxygen and food or produce as much CO2
Why can’t large organisms rely solely on diffusion for gas exchange?
- substances need to travel long distances from the outside to reach the cytoplasm of cells
- large metabolic rate
- very active and control their own body temperature
- high demands for oxygen and food
- higher amounts of CO2 and other waste products produced
State the factors affecting the rate of diffusion
- the surface area
- the concentration gradient
- diffusion distance
What are the features of an effective gas exchange system?
- good blood supply, helps maintain a steep concentration gradient
- large SA:V
- short diffusion distances, think layers
- moist surfaces as most diffusion occurs with gases in solution
- permeable surfaces
State the features of the human gas exchange system which make it effective (nose and chest)
- nasal passages have a high surface area (no gas exchange)
- good supply
- lining of passages secretes mucus and is covered in hair so the external air is prepared
- hairs and mucus clean up dust, small particles and pathogens which get breathed in
- moist surfaces, increase level of water vapour in the air
- rich blood supply raises temperature
State the features of gas exchange in the alveoli which make it effective
- capillaries which run next to alveoli have walls that are one cell thick
- elastic tissues runs between the capillaries and alveoli and helps force air out of the lungs (elastic recoil)
- lung surfactant prevents alveoli from collapsing
- steep concentration gradient as air is being breathed in to the lungs and blood flow removes oxygen in the capillaries
- alveolus surface is folded to form a large surface area
State the features of the gas exchange system in insects
- spiracles
- tracheoles
- tracheae
What is the function of the spiracles?
found along the thorax and abdomen of most insects. they are the site of entry and exit of respiratory gases. can be opened or closed by sphincters which also control water loss
State the function of the tracheae
largest tubes of the respiratory system, carry air directly to the body for gas exchange. supported by rings of chitin which hold the trachea open when the insect moves. chitin is impermeable to gases. the tracheae branch into tracheoles
State the function of the tracheoles
main site of gas exchange, they are minute tubes with no chitin lining. freely permeable to gases
How does the gas exchange system of an insect work?
- air enters spiracles, spiracles are kept shut as much as possible to minimise water loss
- air moves along the trachea and tracheoles by diffusion. large SA of tracheoles due to huge network of tracheoles
- tracheoles can contain water which limits penetration of gases until very active insects produce lactic acid which changes the osmotic potential and causes water to move out by osmosis
- once water has moved out, there is more space for gas exchange to take place
How to active insects supply extra oxygen?
- mechanical ventilation
- collapsible tracheae or air sacs
How does mechanical ventilation work to supply more oxygen?
air is actively pumped into the tracheal system using muscular pumping. it changes the volume and pressure inside the body which draws air in and out
How do collapsible tracheae and air sacs work to supply more oxygen?
they increase the volume of air moved through the system. ventilating movements inflate or deflate them
Define gills
the organs of ogans exchange in fish
