Gas Exchange & Diffusion

Question 1

What is diffusion?

Answer 1

Diffusion is the movement of particles from an area of high concentration to an area of low concentration.

Question 2

During gas exchange oxygen ……… (enters/exits) the lungs

Answer 2

enters

Question 3

During gas exchange carbon dioxide ……… (enters/exits) the lungs

Answer 3

exits

Question 4

Why do complex multicellular organisms require specialised breathing systems? (reference diffusion and surface-area-to-volume ratio)

Answer 4

Multicellular organisms tend to be very big . They don’t have a big enough surface-area-to-volume ratio for oxygen to be able to diffuse to all of their cells. Therefore, a specialised breathing system is required to increase the surface area and make sure there is sufficient gas exchange for bodily functions to take place.

Question 5

What two systems are needed in multicellular organisms, to help with increasing the rate of gas exchange? Explain what they help with.

Answer 5

(1) Respiratory system: to bring oxygen to the blood
(2) Circulatory system: to transport the oxygen to tissues

Question 6

Where does gas exchange take place?

Answer 6

In the alveoli in the lungs.

Question 7

What are some ways that the alveoli are adapted to increase the rate of diffusion?

Answer 7

• short distance (thin alveolar walls, 1 cell thick)
• surface area is large
• moisten air (oxygen dissolves & diffuses quickly)