Foodchem Lecture 10 Pics PART2

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Morgan.liberatore
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142528
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Foodchem Lecture 10 Pics PART2
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2012-03-19 16:03:11
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Foodchem Lecture 10 Pics PART2
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Foodchem Lecture 10 Pics PART2
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    • Various versions of hydrogen bonds
    • Hydrogen bonds are formed as a result of an electron density differential between oxygen and hydrogen
    • Oxygen - electron rich
    • Hydrogen - electron poor
  1. In proteins hydrogen bonding acts as a zipper-like force to lock the protein in a helical conformation
    • Alpha helix close up
    • In proteins hydrogen bonding acts as a zipper-like force to lock the protein in a helical conformation
    • Myoglobin - mostly alpha helix
    • Whether or not a helical structural region form is a function of the amino acid composition (sequence) within the protein
    • Most amino acids contribute to helix formation with the exception of proline and hydroxyproline (imino acids)
    • This is because they do not have a true amino group to contribute
    • If imino acids are present in the chain, the helical structure will be disrupted at that poit and a random sequence may arise
    • Beta pleated sheet
    • If proteins are synthesized side by side or lie parallel to each other, hydrogen bonds can form between chains (inter-molecular hydrogen bonding) to produc a sheet-like structure
    • Two subforms of beta pleated sheets: Parallel and anti-parallel
    • Inter-molecular hydrogen bonding (as opposed to intra-molecular hydrogen bonding for the alpha helix structure)
  2. Parallel beta sheet
  3. Antiparallel beta sheet
    • Mixed alpha, beta forms and random coil
    • Beta sheet structures can be present within the tertiary structure of a protein when chains lie next to each other
    • Suprahelix
    • Found in collagen
    • Composed of 33% glycine, and 25% proline/hydroxyproline
    • 3 separate macromolecules, of which 2 are similar and 1 is different, intertwined
    • Basic unit of a suprahelix - tropocollagen
    • Suprahelix is held together by hydrogen bonding between the chains, with the hydrogen bonds being supplied by glycine
    • Collagen formation
    • Disrupted collagen is extensively used as a gelling and binding agent in food systems
    • Beta pleated sheet and suprahelix are basic structural units which are subsequently assembled into more complex forms

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