More on exchanging substances

Question 1

What diffused into and out of the leaf

Answer 1

co2 diffused into the airspace within the leaf, then it diffused into the cells where photosynthesis happens, leaf’s structure is adapted so that this happens easily.

Question 2

What is the exchange surface in plants ?

Answer 2

the underneath of the leaf.
It covered in little holes called stomata which the co2 diffused in through.
Oxygen and water vapour also diffuse out through stomata.

Question 3

Size of stomata are controlled by

Answer 3

Guard cells. These close the stomata if the plant is losing water faster than is it being replaced by the roots. Without these guard cells the plant would soon wilt.

Question 4

What increases the area of the of this exchange surface so that its more effective ?

Answer 4

flattened shape of the leaf

Question 5

The —– —— ——- —— also form another exchange surface

Answer 5

walls of the cell inside the leaf. The air spaces inside the leaf increase the area of this surface so there’s more chance for co2 to get into the cells.

Water vapour evaporates from the cells inside the leaf. then it escapes by diffusion because there’s a lot of it inside the leaf and less of it in the air outside

Question 6

What is the gas exchange surface in fish and how does co2 diffuse from the blood into the water.

Answer 6

gills
Water enters the fish through its mouth and passes out through the gills. As this happens, oxygen diffuses from the water into the blood in the gills and co2 diffuses from the blood into the water.

Question 7

What is each gills made from ? and how is it specialised ?

Answer 7

lots of thin plates called gill filaments, which gives a big SA for exchange of gases.
The gill filaments are covered in lots of tiny structures called lamellae, which increases the SA even more.
The lamellae have lots of blood capillaries to speed up diffusion

They also have a thin surface layer of cells to minimise the distance that the gases have to diffuse. Blood flows through the lamellae in one direction and water flows over in the opposite direction. This maintains a large concentration gradients between the water and the blood.

Question 8

The concentration of oxygen ..

Answer 8

in the water is always higher than that in the blood. So as much oxygen as possible diffuses from the water into the blood.