Structure
The cell membrane is composed mainly of proteins (55% ),
lipids (42% ) Phospholipids 25 % - cholesterol 13% - other lipids 4% & carbohydrates 3%
A- Lipids
~ 2 layers (bilayer) important for the flexibility & selective permeabi lity of the cell membrane
~ 2 typeS: E x trace ll ular lu l d CarbOh~rato Extracellu lar fl u i d
Phosp holipid ~ '-'
bHoyor ~~
ProtOin S
Polar reg1ons
Intracellular fluid
1. Phospholip ids 2. Cholesterol
Head Tail -Hydrophobic (embedded in
3
- Phosphate group (P0 4 - ) - Free fatty acids (FFA) the phospholipid bilayer)
-Exterior - Interior -Affects the permeability of
- Hydrophilic (loves water) - Hydrophobic (hates water) the membrane & gives
- Charged (polar) - Uncharged (non-polar) toughness to it
Phospholipid molecule is amphipath ic (one part hydrophilic & the other hydrophobic)
B- Proteins
);> Types of cell membrane proteins: (2 types)
1. I ntegral (globular) proteins 2. Separate (peripheral) proteins
Occupy the whole thickness of the membrane Separate at sides of the membrane
);> Cell membrane proteins: (2 parts)
1. Interior (uncharged, hydrophobic) part: in the interior of the membrane
2. Outer: (charged, hydrophilic) part: directed to the surface
C- Carboh d rate
Carbohydrates are present in combination with proteins & lipids ¢ glycoproteins & glycolipids
Functions: 1. Important as recognition sites, in self-differen tiation & immune responses
2. Help in attaching cells together
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