Diffusion (simple & facilitated)

Question 1

Explain the movement of particles in simple diffusion

Answer 1

• All particles are constantly in motion due to the kinetic energy that they possess
• This motion is random, with no set pattern to the way the particles move around
• Particles are constantly bouncing off one another and other objects e.g the sides of the vessel which they are contained

Question 2

Define diffusion

Answer 2

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

Question 3

What type of process is simple and facilitated diffusion?

Answer 3

Passive (energy comes from the motion of the particles not an external source)

Question 4

Describe diffusion through a cell-surface membrane

Answer 4

Only small non-polar molecules can diffuse across cell-surface membranes e.g oxygen + carbon dioxide

Question 5

Describe what happens and what is involved in facilitated diffusion

Answer 5

• Relies on kinetic energy of diffusing molecules
• Movement of charged ions and polar molecules (which do not diffuse easily) by transmembrane channels + carriers
• Has to happen at specific points on the membrane

Question 6

How is the relationship between simple + facilitated diffusion and concentration gradient described?

Answer 6

They both occur down a concentration gradient

Question 7

Describe protein channels and their functions

Answer 7

• Water-filled hydrophilic channels
• Allow specific water soluble ions to pass through
• Channels are selective
• Channel will remain closed unless specific ion is present

Question 8

Describe carrier proteins and their functions

Answer 8

• Molecule that binds to proteins, which causes them to change shape + is then released
• Molecule has to be specific to a protein
• Only uses kinetic energy of molecules