Diffusion through cell membranes

Question 1

Where does gas exchange happen?

Answer 1

In the lungs.

Question 2

What is the job of the lungs?

Answer 2

To transfer oxygen into the blood and to remove waste carbon dioxide.

Question 3

How do the lungs complete gas exchange?

Answer 3

They contain millions of little air sacs called alveoli.

Question 4

What gas exchange takes place in the alveoli?

Answer 4

Gas exchange of oxygen and carbon dioxide.

Question 5

How are the alveoli specialised to maximise diffusion of oxygen and carbon dioxide?

Answer 5

They have:

• An enormous surface area (about 75m² in humans)
• A moist lining for dissolving gases
• Very thin walls
• A good blood supply

Question 6

What is the inside of the small intestine covered with?

Answer 6

Millions and millions of tiny projections called villi.

Question 7

What do villi do?

Answer 7

They increase the surface area of the intestinal walls so that digested food is absorbed more quickly into the blood.

Question 8

What do the villi have?

Answer 8

• A single layer of surface cells.

- A very good blood supply to assist with quick absorption.