1. Cell Membranes

2. Cell Membrane
More than a protection...

3. Cell Membrane Protects the cell.
Allows certain molecules to enter the cell and not others.
Contains the cytoplasm and organelles.
Is constituted by a bilayer of phospholipids, with proteins trapped in the membrane.

4. Membranes are formed of phospholipids.
Phospholipids are amphipathic molecules: they have in the same molecule hydrophilic and hydrophobic regions
Phospholipids are the most abundant lipid in membranes.

5. Phospholipids

6. Simple model of membrane

7. The membrane is fluid “horizontally”

8. “Fluid Mosaic” Model of cell membrane with proteins

9. In this model, you see how the cytoskeleton attaches to proteins of the membrane

10. There are also proteins attached to the membrane
There are also proteins attached to the membrane. They have various functions.

12. Passive diffusion: from a high concentration to a low concentration.

13. Passive transport: Use a protein as a carrier, or channel, from high concentration to low concentration.

14. Osmosis: Diffusion of water only.

15. Comparing two different concentrations of solutes.
Hypertonic: the solution with the higher concentration
Hypotonic: the solution with the lower concentration.
Isotonic: same concentration of solute.

16. Osmosis: Hypertonic, Hypotonic

17. Facilitated diffusion by transport

19. Ligand Gated channels

20. Active transport
Against the concentration gradient, from low to high concentration.
Requires energy.
Uses a transmembrane protein for transport

21. Types of active transports

22. Transport by vesicle
Endocytosis:
Phagocytosis
Pinocytosis

23. Receptor mediated endocytosis (coated pits)

25. Exocytosis