Structures of proteins (the 4 organization levels)

                                   

(1) Primary structure: The order of sequence of amino acids
(2) Secondary structure: the alpha helix and beta-pleated sheet
(3) Tertiary structure: protein folding (i.e. 3- dimensional structure)
(4) Quarternary structure: when a protein contains more than one polypeptide chain (subunits), the way in which the subunits are                                          packed together.

 

 

Select "Cartoons" from the "Display" menu and you will see what alpha helix is:

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