When a protein is denatured by heat

  • A. its peptide bonds are hydrolysed and amino acids are released
  • B. its tertiary structure is destroyed but its primary structure remains intact
  • C. its amino acid sequence is rearranged
  • D. it becomes more soluble and more active

Explanation

Heat breaks the relatively weak hydrogen, ionic and hydrophobic interactions that hold the chain in its three dimensional shape, so the protein unfolds and loses function, but the strong covalent peptide bonds of the backbone survive. This is why boiling an egg changes the albumen irreversibly without breaking it into amino acids. Denatured proteins usually become less soluble, which is why the egg white turns opaque.

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