The Plasma Membrane Thickness of 7 - 8 nm You would need 10 000 membranes to add up the thickness of one sheet of paper

The Plasma Membrane Function: Structure: Selective passage of certaine substances during transport through the membrane Structure: Lipid bilayer A) phospholipis B) cholesterol C) glycolipids Proteins Cholesterol

Lipid bilayer cholesterol phospholipids glycolipid

phospholipids Structure: Hydrophilic Region Polar head Oriented towards the aquatic region Hydrophobic Region Non-polar Tails Oriented towards the inside of the bilayer Functions: Fluidity of the membrane Selective permeability

Unsaturated fatty acids phospholipid Formation Saturated fatty acids tail Unsaturated fatty acids tail Right Is Bent

Properties of the phospholipids Repair: If the membrane is pierced, the separated molecules of phospholipids can come together and close the opening. Modification: The molecules of phospholipids can add more phospholipids or take some away to change the volume of the cell. Division: During division, the center of the cell can separate and form two cells. Two cells can also join together to create one.

Properties of phospholipids Selective Permeability: Permeable: To lipo-soluble molecules, and to very small molecules (O2 et CO2) Impermeable: Big molecules, and to ions (K+ , Na+, Cl -)

Le cholestérol représente Cholesterol Functions: Reduce the fluidity of the membrane Stabilise the membrane Increase the rigidity of the membrane. Situated between the molecules of phospholipids in the bilayer. Le cholestérol représente de 15 à 50% des lipides

Glycolipid/ Marker Glyco for glucose = sugar Lipid = fatty acid Participates in the formation of glycolipids The glycolipds are situated on the external surface of the membrane Functions: Gives a cellular identity Permits cellular adherence (stick together)

Proteins 3 types: Marker (Glycoproteins): glucose chaine attached on a protein Receptor (hormone): Receives instructions, communication TRANSPORT PROTEINS Carrier Proteins (Peripheral proteins) : placed one next to the other in the bilayer Channel (Intrinsic proteins) : extends through the bilayer

Functions of the proteins Canal: permits the passage of certain substances across the membrane Transporter: transports molecules from one side to the other Receptor: recognizes specific substances and modifies the activities of the cell. Receives instructions. Recognition: Gives a cellular identity. Adherence: Permits cellular adherence (stick together), which increases stability

Fluid mosaïc Model Mosaïc: the composition of the membrane is heterogenous (not the same) Fluid: the molecules move: laterally (~107 times/seconde), they rotate and flip-flop (~ 1 time/month) http://coproweb.free.fr/pagphy/physioan/ch1s5.htm

Functions of the Cell Membrane Selective passage of substances across the membrane Passive Transport Active Transport Diffusion (Simple or passif) Osmosis Pump Exocytosis Facilitated Diffusion Endocytosis