4.2 Diffusion

Question 1

What is diffusion?

Answer 1

The net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower until it evenly distributed.

Question 2

Why is facilitated diffusion necessary?

Answer 2

only small, non-polar molecules can diffuse across the cell-surface membrane easily.

Question 3

How do protein channels perform facilitated diffusion?

Answer 3

• they are hydrophilic so allow water-soluble ions through.
• they are selective, and only let certain ions through
• the ions bind to it, causing it to change shape which causes it to open on one side and close on the other.

Question 4

How do carrier proteins perform facilitated diffusion?

Answer 4

• when ions specific to the protein are present, the protein changes shape so the molecule is released into the inside of the membrane.