2.5.3 Diffusion & Facilitated Diffusion

Question 1

Diffusion Def

Answer 1

Net movement of molecules or ions a as result of random motion (kinetic energy) of a substance from a region of higher concentration to a lower concentration

Question 2

How can large polar molecules or ions diffuse across cell membranes?

Answer 2

• Via facilitated diffusion by transport proteins
• Channel proteins or carrier proteins
• Highly specific

Question 3

What are channel proteins?

Answer 3

• Gated proteins
• Molecules are let through WITHOUT A CHANGE IN SHAPE
• Allow exchange of ions

Question 4

What are carrier proteins?

Answer 4

• Switch between 2 shapes
• Binding sites of carrier proteins change shape
• Net diffusion of molecules or ions occurs down a concentration gradient

Question 5

Why can’t glucose diffuse through a cell membrane?

Answer 5

• Glucose molecule is too large
• And phospholipids act as a barrier
  OR
• Glucose molecules are insoluble in phospholipids because of polar OH- groups