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Regarding the secondary structure of proteins, I know that there are 3 main types. The beta sheet formation is made up of beta strands stabilized by hydrogen bonds to form an anti parallel or a parallel structure. I learned that these beta strands are a zigzag sequence of amino acids, but what traits of beta strands differentiate it from the primary structure? Or are the beta strands just primary structures that link together to make beta sheets?

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    $\begingroup$ Primary structure when talking about proteins refers only to the aminoacid sequence, it does not refer to any spacial/3D structures like beta strands.. $\endgroup$ – Maljam Apr 5 '16 at 9:46
  • $\begingroup$ This is a little confused. Secondary structure usually refers to helices and sheets. Sheets are made up of strands that can be either parallel or anti-parallel. $\endgroup$ – gilleain Apr 5 '16 at 10:19
  • $\begingroup$ See here for a great account by Perutz of his own reaction to the discovery of the alpha-helix by Pauling and Corey. Also a great introduction to secondary structure (alpha-helix and beta-sheet). (I wish I had make you angry earlier, by Max Perutz) $\endgroup$ – user1136 Apr 5 '16 at 13:54
  • $\begingroup$ As @gilleain said secondary structure is the Beta pleated sheet and not the Beta strands. $\endgroup$ – Tyto alba Sep 6 '16 at 7:34
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primary structure
focus = peptide bonds (because these link the amino acids
The sequence of amino acids, for example AGGVHIL..
enter image description here
secondary structure
focus = H-bonds between the parts of the backbone
There are several different types of secondary structure (α-helices, β-sheets, etc.). However the most import thing to remember is that the secondary structure refers to the the patterns of hydrogen bonds formed between amine hydrogen and carbonyl oxygen atoms contained in the backbone peptide bonds of the protein
enter image description here
your confusion
You are partly correct from a very simple perspective you can see the secondary structure of β-Sheets just as connected primary structures. However when talking about a piece of secondary structure you have to take the hydrogen bonding into consideration as this is what connects your primary structure parts (β-strands) to form a β-sheet.

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