Exchange Surfaces

Question 1

What can cells use to take in substances they need ?

Answer 1

Cells can use diffusion to take in substances they need and get rid of waste products for example,

Oxygen and carbon dioxide are transferred between cells and the environment during gas exchange

In humans, urea (a waste product from the breakdown of proteins) diffuses from cells into the blood plasma for removal from the body by the kidneys

Question 2

How to calculate surface area to volume ratio

Answer 2

The larger the organism is, the smaller it’s surface area is compared to its volume

SA:V
Surface area to volume ratio

Find the area of the surface
LXW
Find the volume
LXWXH

The volume is usually smaller than the surface area

Question 3

Why is it that gas and dissolved substances can diffuse directly into the cell ?

Answer 3

Gases and dissolved substances can diffuse directly into the cell because they have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell

Question 4

Do multicellular organisms have a larger or smaller surface area ?

Answer 4

Multicellular organisms have a much smaller surface area compared to their volume this means they need some sort of exchange surface for efficient diffusion

Question 5

Exchange surfaces are adapted to maximise effectiveness…

Answer 5

They have a thin membrane so substances only have a short distance to diffuse

They have a large surface area so lots of substances can diffuse at once

Exchange surfaces in animals have lots of blood vessels to get in and out of the blood quickly

Gas exchanges in animals e.g, alveoli are often ventilated- air moves in and out