4.2 Diffusion

Question 1

Define diffusion

Answer 1

The net movement of molecules or ions from an area where they are more highly concentrated to an area where their concentration is lower until evenly distributed

Question 2

State three factors that affect the rate of diffusion

Answer 2

-Larger concentration gradient=faster
-Larger surface area= faster because there are more points of access for diffusion to occur
-Shorter diffusion distance=faster because less distance that molecules have to travel

Question 3

Describe facilitated diffusion

Answer 3

Diffusion along a concentration gradient involving carrier proteins and protein channels
Passive process (doesn’t require ATP)
Occurs at specific points on the plasma membrane where there are channel and carrier proteins

Question 4

How do protein channels work?

Answer 4

-Water filled hydrophilic channels across the membrane
-Allow specific water soluble ions to pass through
-If the particular ion is not present the channel remains closed
-Ion binds with the protein causing it to change shape in a way that closes it to one side of the membrane and opens it to the other side

Question 5

How do carrier proteins work?

Answer 5

-When a specific molecule is present it binds to the protein
-This causes it to change shape in such a way that the molecule is released to the inside of the membrane