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Cell Membrane

Cell membrane

I). Plasma (cell) Membrane

        A). Structure

            1). Lipid Bilayer

Consists of a double layer of phospholipids :
bullethydrophilic= polar phosphorous head

attract water and face the inner and outer environment

bullet hydrophobic= nonpolar fatty acid tail

avoid water and line up in the center of the membrane

               Permeable to molecules that are soluble in lipids:

Not permeable to molecules that are soluble in H2O:

 

            2). Proteins

                                Provide specialized functions for the cell

  i).  Receptor Proteins

                         Bind with external molecules (hormones) and

                        then carry messages into the inside of the cell

ii).  Integral proteins

    Act as channels for ions.

       iii). Peripheral proteins:

Associated with part of the membrane and act as enzymes and in signal transduction.

      iv).  Glycoproteins contain a branching sugar

                            Function in cell adhesion and cell recognition. 

 

            3). Cholesterol

 

        B). Function of cell membrane:

 

        C). Membrane Junctions

1). Tight junctions

2). Desmosomes

3). Gap junctions

 

        D). Cell Adhesion Molecules

                Sticky glycoprotein

1). Selectin

2). Integrin