1. Diffusion

2. Diffusion
Is a passive (no energy is required) process of moving molecules / substances from one area to another!
It involves moving the substances down a concentration gradient from a high to a low solution!

3. Diffusion
High concentration is an area where there is a lot of the substance / molecules in question.
The low concentration is the opposite. . An area where there are only a few molecules of the substance!

4. MINDMAP

5. Diffusion - Introduction
The exchange of substances between cells and the environment occurs in ways that require metabolic energy (______________ ) and in ways that do not (_____________ ). Diffusion is an example of _____________ .
ACTIVE TRANSPORT
PASSIVE TRANSPORT
PASSIVE TRANSPORT

6. Diffusion is……..
The passive, net movement of particles from an area of high concentration to an area of low concentration, until equilibrium is reached. Due to the random movement of particles. The more kinetic energy the particles have, the faster diffusion occurs.

7. Diagrammatic version……..

8. Facilitated Diffusion
Exactly the same principles as simple diffusion: Down a concentration gradient Passive Uses Carrier Proteins or Channel Proteins.

9. Carrier Proteins Carry large water soluble substances e.g. glucose
Specific molecules binds with the proteins
Causes it to change shape
Molecule is released on the other side of the membrane (the carrier protein then converts back to its original shape)
No external energy is required
Kinetic energy of the molecules themselves is all that’s needed

10. Carrier Proteins
Bind to the substances and undergoes structural changes that allow them to carry the molecules through the membrane

11. Facilitated Diffusion

12. Channel Proteins water filled pores, carry ions e.g. Na+ and Ca2+
Water filled channels
Molecules such as glucose, amino acids can pass through
Selective, only specific molecules are let through
If the molecule is not present they remain closed.
Control entry and exit of substances

13. Extracellular space Cytooplasm (aqueous)
High concentration
Fat-soluble organic molecules can diffuse through the bilayer but polar molecules require proteins
Fat-soluble molecules
Polar molecules
Extracellular
space
Ion channel
Cytooplasm
(aqueous)
Low concentration
hydrophilic pore

14. Passive (no energy required)
Give 2 ways in which facilitated diffusion and simple diffusion are similar and one way in which they are different.
Similarities
Passive (no energy required)
Particles move down their concentration gradient
Differences
Facilitated diffusion uses proteins

15. Rate of diffusion!
Diffusion is faster in gasses than in solutions! Liquid molecules have lower levels of energy to move and also have to change direction more as the particles are much closer together!

16. Concentration gradient!
The steeper the gradient the faster the rate of diffusion!
High concentration
Low concentration

17. The concentration gradient decreases with distance
High concentration of Carbon dioxide
Low concentration of Carbon dioxide A B
Diffusion rate decreases the further away from the cell membrane the organelles are!

18. Size of the particles
Smaller particles like oxygen move faster than carbon dioxide. So the rate of diffusion also depends on the size!

19. Active Transport

20. Active Transport
Inside of cell Outside of cell
ATP
ADP P