1. What molecules cross the cell membrane
What molecules cross the cell membrane? How do these molecules cross the cell membrane? *

2. The phospholipd bilayer is permeable to gases, water and lipids.

3. Gases, water and lipids can pass through. the cell mb
Gases, water and lipids can pass through the cell mb. These diffuse through the mb. *

4. Characteristics of diffusion: *molecules are always moving**
Down a concentration gradient
Diffusion rate depends on the steepness of the concentration gradient
Kinetic energy from molecules that are moving
Eventually the molecules distribute themselves evenly (equilibrium).
Molecules diffuse short distances quickly.

5. Characteristics of diffusion:
Diffusion is directly related to temperature
Diffusion is inversely related to molecular size
Diffusion can occur in an open system
Diffusion can occur across a barrier if the molecule can cross the barrier

6. Diffusion rate of lipophilic molecules across the cell mb (phospholipid bilayer)
Diffusion rate depends of solubility in lipid layer
Diffusion rate depends on the surface area of the cell mb.
Faster diffusion with thinner mb (short distance to cross)

7. Ions diffuse through channels down their concentration gradient.
Ca++
Ca++
Ca++

8. How do the rules of diffusion apply to movement by carrier proteins?

9. Carrier mediated transport into cells: - net movement as long as there is a concentration gradient across the mb  Facilitated Diffusion
Diffusion and carrier proteins

10. Carrier mediated transport into cells: Specificity
Eg. Glucose transporters move 6 carbon sugars (hexoses).

11. Carrier mediated transport into cells: Specificity
Glucose transporters will not move maltose.

12. Carrier mediated transport into cells: Competition
6 carbon sugars bind to the glucose carrier
The carrier has a higher affinity for glucose than for fructose or galactose
Glucose moves into the cell faster than the others

13. Carrier mediated transport into cells: Competition
Only galactose
Glucose and galactose

14. Carrier mediated transport into cells: Competition
A competing molecule can block the transport

15. Carrier mediated transport into cells Saturation
Carriers transporting a substrate reach their maximal rate.
Diffusion and carrier proteins

16. Carrier mediated transport into cells Saturation

17. Cells need glucose as a source of ATP for energy.
How can I get my glucose?

19. Carrier mediated transport into cells.