Exchange Of Materials

Question 1

The ______ an organism is, the ______ it’s surface area: volume ratio.

Answer 1

The larger an organism is, the smaller it’s surface area: volume ratio.

Question 2

Alveoli

Answer 2

Little air sacs in lungs where gas exchange takes place.

Question 3

How do alveoli work

Answer 3

Blood arriving to alveoli has returned to lungs from the body so contains lots of CO2 and not much O2. - this maximises concentration gradient for diffusion of both gases.
O2 diffuses out of the air in the alveoli ( where concentration of O2 is high) and into the blood (where O2 concentration is low).
CO2 diffuses in opposite direction to be breathed out.

Question 4

How are alveoli adapted to their function?

Answer 4

Specialised to maximise diffusion of O2 and CO2:
Moist lining for dissolving gases
Good blood supply to maintain concentration gradients
Thin walls minimising distance gases have to move.
Big surface area

Question 5

What’s concentration gradient

Answer 5

Big ‘Difference in concentration’ will make substances diffuse faster.