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    can someone explain what these are? (i no its something to do with protiens and amino acids)

    its for nuffild unit 5 food science section

    cheers amo1
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    Proteins are chains of amino acids joined by amide (CONH) bonds.
    When you get the initial chain of amino acids you get hydrogen bonds and disulphide bridges between certain points along the chain to give it it's specific structure.the alpha helix is just a coil shape, looks like a spiral staircase, but without the steps. Hmm.
    The beta pleat is when two adjacent stretched out chains of amino acids form hydrogen bonds between the chains. Adjacent C=O and N-H bonds have dipoles.Looks like a straight ladder, but the horizontal rungs are H-bonds.

    Hope this helps.
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    The alpha helix and beta sheet are both example of secondary structure of proteins. The primary structure is simply the order of the amino acids whereas the secondary structure is concerned with the bonding between the amino acids. In the alpha helix you have two parallel chains with hydrogen bonding between the amine group and the acid group [N-H...O=C] which then makes them twist into a helix. The difference with beta sheets is the chains are arranged side by side and there is hydrogen bonding between all the chains, to make a sheet structure.

    I'm doing unit 5 and I only know the above from Biology, I don't think you need too much detail for the actual exam just need to know that alpha-helix is a secondary structure and that it involves hydrogen bonding.
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    Actually, alpha helices are not two strands H-bonded together but one strand curled around and H-bonded to itself to give it stability.
    Beta sheets can be several strads all together in a zig zag shape and H-bonded together.
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    (Original post by oxymoron)
    Actually, alpha helices are not two strands H-bonded together but one strand curled around and H-bonded to itself to give it stability.
    Beta sheets can be several strads all together in a zig zag shape and H-bonded together.
    Which way do they zig zag? Does it matter?
    I mean, if you were to lay a single sheet of amino acid chains out H-bonded together and looked straight down on the parallel chains, would the zigs zigs be left-right or towards and away from you? I'm presuming its towards and away...not that I'm losing sleep over it or anything....
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    (Original post by oxymoron)
    Actually, alpha helices are not two strands H-bonded together but one strand curled around and H-bonded to itself to give it stability.
    Ah didn't know that..thank you very much
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    so something like dna would be alpha?
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    No - alpha helix refers only to proteins.
    DNA structure is known as a double helix (and in fact comes in three types: A, B and Z)
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    so betya is a striaght ladder
    and alpha is one thats h bonded to itself in a big ball
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    (Original post by amo1)
    so betya is a striaght ladder
    and alpha is one thats h bonded to itself in a big ball
    Here is a pic to illustrate what I mean.
    pink is the alpha helix
    yellow is the beta pleated sheet

    http://cmgm.stanford.edu/biochem218/.../proteinss.gif
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    To clear up the alpha / DNA bit
    what Seth described (with 2 strands) is the structure of DNA which is called a double helix
    What oxymoron described with a single strand is the alpha helix found in proteins such as insulin
 
 
 
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