hoe does gas exchange occur? Flashcards
how does gas exchange occur?
1) diffusion through cell surface membrane
2) gills
3) tracheal tubes
4) lungs
5) stomata in leaves
what characteristics does a good exchange surface have?
- large surface area
- thin
- stew concentration gradient maintained at all times
- permeable to gases
what is the exchange surface got in single celled organisms?
- large SA:V
- low metabolic rate
- thin
what is the exchange surface got in multicellular organisms? eg . a tape worm
- SA : V is too small to reply on diffusion - body shape adapts to maximise surface area
how do you work out the volume of a cylinder?
pie x radius squared x length
what is the volume of a sphere?
4/3 x pie x radius cubed
why do larger mammals need a more specialised system? what is necessary?
higher metabolic rate
maintenance of a steep concentration gradient
what does it mean by terrestrial animals?
mostly insects
to reduce water loss terrestrial exhibit what features?
- waterproof coverings over body —> exoskeleton
- small SA:VOL
explain has exchange in insects to do with the tracheae system
tracheae divide into tubes called tracheoles —> these extend to all the musvlentodsues of an insect —> gas diffuses into liquid at end of
—> gas enters insects by spirals
what are the lungs enclosed in?
an airtight compartment called the thorax
what lines the thorax and covers each lung?
pleural membranes
why is there fluid between the membranes?
prevents friction between lungs as the move
what surrounds the thorax?
the ribs
what are the two stages on ventilation?
inspiration and expiration
what happens in the inspiration?
diaphragm contracts and moves down
volume of thorax increases
air moves into lungs
what happens expiration?
diaphragm relaxes
ribs move down
volume of thorax decreases
pressure outside is lower than pressure inside
why is lung tissue elastic?
because it will recoil to its original position after being stretched —> helps to force air out of lungs
what are the insides of the alveoli coated with? what does this allow?
surfactant —> gases to dissolve and rapid diffusion
what does surfactant help prevent?
the alveoli from collapsing during exhalation
why is gas exchange efficient in the alveolus?
- moist
- short diffusion pathway
- large SA
- large diffusion gradient is maintained
what do plants do in the day?
photosynthesise and respire , co2 is taken in and oxygen is released
what do plants do at night?
no sunlight so plants only respire therefore oxygen is taken in and co2 comes out
what are the 3 steps of how gases enter and leave a leaf?
- gases diffuse in and out of leaves by the stomata
- move down the concentration gradient
- oxygen diffuses into the sub-stomatal air chambers through intercellular spaces into cells
how are leaves adapted for gas exchange?
- large surface area —> room for lots of stomata—> capture as much light as possible
- thin —> diffusion pathway is short —> light penetrates through leaf
- air space in spongy mesophyll —> allows oxygen and co2 to diffuse between stomata and cells —> allows co2 to diffuse
how do gases enter and leave the leaf?
through the stomata
what is each pore on the stomata lined with?
two guard cells
if water enters the guard cells they become…?
turgid and swell and the pore opens
if water leaves the guard cells they become…?
flaccid and the pore closes
how does water enter the cell?
chloroplasts in the guard cells photosynthesise producing ATP —> energy for potassium ions to move into guard cells
stored starch into malate
malate and potassium ions lower water potential in guard cells making it negative therefore water enters by osmosis
stomata closes when..?
to prevent water loss
in bright light to prevent water loss
