Membrane

 

Fluid-mosaic model

Permeability

A) Not allow to pass:

1. inner layer of the phospholipid layer, which is hydrophobic, forms a physical barrier to those polar substance

B) Allow to pass:

1. phospholipid bilayer allows fat soluble molecules and small uncharged molecule e.g:O2,CO2 to diffuse freely pass through
2. channel protein form open pores for (facilitated) diffusion of small polar substance to pass through

C) Carrier protein:

1. carrier protein bind with specific molecule and bring them to the opposite side of the membrane
2. carrier protein allow facilitated diffusion of some molecule

Factors affecting the permeability

1. Temperature
2. fat soluble substance
3. charge of the polar particule
4. lipid visocity

Function

1. Compartmentalization
2. Control exchange
3. Site of membrane-binded enzymatic reaction
4. recognition
5. cell and organic identity
6. endocytosis
7. extocytosis
8. myelin sheath insulutes

 

* try to think the composition of cell membrane first