gas exchange in plants and insects

Question 1

what is the gas exchange surface in a leaf?

Answer 1

spongy mesophyll

Question 2

how does a leaf provide a short diffusion pathway and large SA?

Answer 2

the leaf is only a few cells thick and is very long

Question 3

how does carbon dioxide enter the leaf?

Answer 3

carbon dioxide diffuses into the intercellular spaces of the leaf via stomata, through the cell wall and cell membrane to enter the
spongy mesophyll cells

Question 4

how does the spongy mesophyll give a large surface area?

Answer 4

air spaces give a large SA over which the CO2 can diffuse into the cells

if cells were tightly packed together little or their surface would be in contact with air

Question 5

how is a concentration gradient maintained in a spongy mesophyll cell?

Answer 5

within the cells, carbon dioxide is used for photosynthesis so concentration of CO2 is maintained at a lower conc in the cell than within the intercellular spaces.

Question 6

why do plants not need complex features for gas exchange?

Answer 6

large surface area from many leaves and lower metabolic requirements than animals

Question 7

how is water loss from exchange surfaces reduced in a leaf?

Answer 7

waterproofing from the waxy cuticle and guard cells that can close the stomata