1.3.1 Diffusion

Question 1

Diffusion

Answer 1

The net movement of particles of a gas or solute from an area of a higher concentration gradient to an area of a lower concentration gradient

Question 2

Exchange surface

Answer 2

A surface where materials are exchanged between an organism and its environment

Question 3

Why are exchange surfaces necessary in multicellular organisms

Answer 3

• Multicellular organisms are more metabolically active, so they need to exchange more substances with the environment
• The surface area to volume ratio is too small

Question 4

Factors that effect diffusion

Answer 4

Large surface area
Thin walls
Good blood supply/ supply of new materials
High temperature

Question 5

Large surface area

Answer 5

In the same time period, more particles can diffuse across the exchange surface

Question 6

Thin walls

Answer 6

Diffusion is slow, so a shorter distance means this takes less time

Question 7

Good blood supply/ supply of new materials

Answer 7

Maintains a steep concentration gradient

Question 8

High temperature

Answer 8

A high temperature increases the kinetic energy in cells, which makes diffusion quicker

Question 9

Substances exchanged between cells and the environment

Answer 9

In:
Oxygen
Water
glucose
Fatty acids and glycerol
Out:
Carbon dioxide
Urea

Question 10

Transport system

Answer 10

A structure that moves materials around the body of multicellular organisms

Question 11

Why are single-celled organisms able to rely on diffusion?

Answer 11

-The surface are to volume ratio is large
-So they only need diffusion as there is a short distance from the outside to the centre if the cell