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AS biology > hoe does gas exchange occur? > Flashcards

hoe does gas exchange occur? Flashcards

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1
Q

how does gas exchange occur?

A

1) diffusion through cell surface membrane
2) gills
3) tracheal tubes
4) lungs
5) stomata in leaves

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2
Q

what characteristics does a good exchange surface have?

A
  • large surface area
  • thin
  • stew concentration gradient maintained at all times
  • permeable to gases
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3
Q

what is the exchange surface got in single celled organisms?

A
  • large SA:V
  • low metabolic rate
  • thin
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4
Q

what is the exchange surface got in multicellular organisms? eg . a tape worm

A
  • SA : V is too small to reply on diffusion - body shape adapts to maximise surface area
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5
Q

how do you work out the volume of a cylinder?

A

pie x radius squared x length

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6
Q

what is the volume of a sphere?

A

4/3 x pie x radius cubed

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7
Q

why do larger mammals need a more specialised system? what is necessary?

A

higher metabolic rate

maintenance of a steep concentration gradient

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8
Q

what does it mean by terrestrial animals?

A

mostly insects

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9
Q

to reduce water loss terrestrial exhibit what features?

A
  • waterproof coverings over body —> exoskeleton

- small SA:VOL

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10
Q

explain has exchange in insects to do with the tracheae system

A

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

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11
Q

what are the lungs enclosed in?

A

an airtight compartment called the thorax

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12
Q

what lines the thorax and covers each lung?

A

pleural membranes

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13
Q

why is there fluid between the membranes?

A

prevents friction between lungs as the move

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14
Q

what surrounds the thorax?

A

the ribs

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15
Q

what are the two stages on ventilation?

A

inspiration and expiration

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16
Q

what happens in the inspiration?

A

diaphragm contracts and moves down
volume of thorax increases
air moves into lungs

17
Q

what happens expiration?

A

diaphragm relaxes
ribs move down
volume of thorax decreases
pressure outside is lower than pressure inside

18
Q

why is lung tissue elastic?

A

because it will recoil to its original position after being stretched —> helps to force air out of lungs

19
Q

what are the insides of the alveoli coated with? what does this allow?

A

surfactant —> gases to dissolve and rapid diffusion

20
Q

what does surfactant help prevent?

A

the alveoli from collapsing during exhalation

21
Q

why is gas exchange efficient in the alveolus?

A
  • moist
  • short diffusion pathway
  • large SA
  • large diffusion gradient is maintained
22
Q

what do plants do in the day?

A

photosynthesise and respire , co2 is taken in and oxygen is released

23
Q

what do plants do at night?

A

no sunlight so plants only respire therefore oxygen is taken in and co2 comes out

24
Q

what are the 3 steps of how gases enter and leave a leaf?

A
  • 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
25
Q

how are leaves adapted for gas exchange?

A
  • 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
26
Q

how do gases enter and leave the leaf?

A

through the stomata

27
Q

what is each pore on the stomata lined with?

A

two guard cells

28
Q

if water enters the guard cells they become…?

A

turgid and swell and the pore opens

29
Q

if water leaves the guard cells they become…?

A

flaccid and the pore closes

30
Q

how does water enter the cell?

A

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

31
Q

stomata closes when..?

A

to prevent water loss

in bright light to prevent water loss

AS biology (17 decks)

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