2.1.1 - Properties Of Gas Exchange Surfaces

Question 1

What Do All Living Organisms Do?
(2 Points)

Answer 1

~ Respire by taking in oxygen and releasing carbon dioxide.

~ These gases then diffuse across a surface called the gas exchange surface.

Question 2

What Are Properties Of Gas Exchange Surfaces?
(3 Points)

Answer 2

~ SA:V ratio.

~ Diffusion pathway.

~ Concentration gradient.

Question 3

Describe ‘SA:V Ratio’ As A Property Of Gas Exchange Surfaces
(3 Points)

Answer 3

~ Surface area refers to the total area of the organism that is exposed to the external environment.

~ Volume refers to the total internal volume of the organism.

~ As organisms increase in size the SA:V ratio decreases.

Question 4

As Organisms Increase In Size Their SA:V Ratio Decreases, Explain This
(2 Points)

Answer 4

~ There is less SA for the absorption of nutrients and gases.

~ The greater volume results in a longer diffusion distance to the cells and tissues.

Question 5

How Have Large Multicellular Organisms Adapted To Increase The Surface Area For Exchange Of Gases?
(3 Points)

Answer 5

~ Alveoli, increase the SA in the mammalian lung.

~ Fish gills, have things called lamellae, providing a large SA.

~ Leaves have a spongy mesophyll layer, leaving a large area of leaf cell surface exposed to the air.

Question 6

Single Celled Organisms Have A High SA:V Ratio, Explain This
(2 Points)

Answer 6

~ Large surface area allows for maximum absorption of nutrients and gases.

~ Small volume within the cell means the diffusion distance to all organelles is short.

Question 7

Describe ‘Diffusion Pathway & Thickness Of Surface’ As A Property Of Gas Exchange Surfaces
(2 Points)

Answer 7

~ Distance across an exchange surface is very short.

~ The surface often contains only one layer of epithelial cells, providing a short diffusion distance.

Question 8

Describe ‘Concentration Gradient’ As A Property Of Gas Exchange Surfaces
(4 Points)

Answer 8

~ It is the difference in concentration of the exchange substances on either side of the exchange surface.

~ A greater difference in concentration means a greater rate of diffusion.

~ The continued movement of exchanges substances away from the exchange surface means that a concentration gradient is maintained.

~ E.g. Alveoli have a good blood supply, constantly removing oxygen from capillary side of the exchange surface and supplies CO2.