More on exchanging substances

Question 1

where are the villi

Answer 1

inside the small intestine

Question 2

how do they increase the speed of absorption of digested food into the blood

Answer 2

they increase the surface area

Question 3

give two details of the villi

Answer 3

a single layer of surface cells

a very good blood supply to assist quick absorption

Question 4

how do the structure of leaves let gages diffuse in and out of cells

Answer 4

underneath a leaf is an exchange surface covered in tiny holes called stomata - this is where the CO2 diffuses through as well as oxygen and water vapour
it’s size is controlled by guard cells that close the stomata if the plant is losing water faster that it’s being replaced

Question 5

how are gills adapted for gas exchange

Answer 5

they have a large surface area
water enters through the mouth and leaves through the gills whilst oxygen diffuses into the blood and CO2 into the water
gill have lamellae that increase surface area and speed up diffusion because of their vast amount of blood capillaries