Diffusion through cell membranes and exchange surfaces

Question 1

Where are tiny projections called Villi located in the human body?

Answer 1

The small intestine

Question 2

What do Villi provide?

Answer 2

A large surface area

Question 3

How is a big surface area for the villi useful?

Answer 3

The villi increase the surface area so that digested food is ABSORBED much more quickly into the blood.

Question 4

What do the villi have?

Answer 4

They have a single layer of surface cells

Good blood supply to assist quick absorption

Question 5

What happens to the digested food?

Answer 5

The digested food moves into the blood by DIFFUSION and by ACTIVE TRANSPORT

Question 6

What happens in the lungs?

Answer 6

Gas Exchange

Question 7

What is the main function of the lungs?

Answer 7

To transfer OXYGEN to the BLOOD and to remove WASTE CARBON DIOXIDE from it.

Question 8

How do the lungs transfer oxygen and remove waste carbon dioxide?

Answer 8

The lungs contain millions of air sacs called ALVEOLi where GAS EXCHANGE takes place.

Question 9

Why are the alveoli specialised?

Answer 9

In order to maximise the diffusion of oxygen and carbon dioxide.

Question 10

4 things that the ALVEOLI have to MAXIMISE DIFFUSION?

Answer 10

1) enormous surface area
2) moist lining for dissolving gases
3) very thin walls
4) a rich blood supply

Question 11

How do Villi increase the rate of diffusion of food molecules?

Answer 11

Provide a massive surface area, increased even more by tiny folds,, microvilli
They have a very rich bloody supply
with a dense network of capillaries which means any food molecules diffuse into the villi, rapidly taken away
Ensures steep conc gradient= rate of diffusion fast
Villi have a thin surface, small food molecules only have to diffuse a small distance before reaching the bloodstream.