Sun, Oct-10-04, 13:02
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Senior Member
Posts: 787
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Plan: Lyle Style FD
Stats: 143/124.5/123
BF:24.8%
Progress: 93%
Location: Huntsville, AL
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Whee, a question I can answer!
Quote:
Originally Posted by Built
Okay, I hear this from time to time, the "denaturing" thing, but isn't that what cooking DOES to protein - ALL protein? And I'd love to understand why this is a problem. Actually, I don't even really understand what "denaturing" means.
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Protein has 4 tiers of structure; 1) PRIMARY -- amino acid sequence, 2) SECONDARY -- alpha helix or beta sheet (the manner in which the protein chain arranges itself), 3) TERTIARY -- the larger folding and arrangement of the helix or sheet and includes cross-linking via disulfide bonds, hydrogen bonds, salt bridges, or hydrophobic interactions, and 4) QUATERNARY - an aggregation of separate protein chains into a larger globule (hemoglobin is an example - it has 4 protein chains combined to make a larger globular protein)
Denaturation -- the hydrogen bonds that hold together the tertiary structure of a protein are disrupted by heat. Heat also destroys the alpha-helical (secondary) structure. The protein chains are unfolded, and therefore can't fit with other protein chains during chemical reactions. An example of this might include a protein and the digestive enzyme (another protein) that helps to digest it. Each enzyme has an active site that accepts only a specific shape. If a protein is denatured and its shape is changed, it will no longer fit into the enzyme and can't be broken down.
Other things denature proteins besides heat. The chemicals used to perm hair denature the hair protein molecules, allowing them to be "curled" or "straightened".
Now, as to what specifically happens to whey protein when heated, I haven't a clue.
Joan the chemistry teacher.
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