Protein Structure
Proteins are formed by linking the amine
nitrogen of one amino acid with a carbon
atom on another amino acid, and then
repeating this “peptide bond” to make a chain
dozens or hundreds of amino acids long. The
carbon-nitrogen backbone of the protein
molecule forms a sort of zigzag pattern, with
the “side groups” — the other atoms on each
amino acid — sticking out to the sides.
The Protein Helix One effect of the peptide
bond is a certain kind of regularity that causes
the molecule as a whole to twist and form a
spiral, or helix. Very few proteins exist as a
simple regular helix, but those that do tend to
join together in strong fibers. These include
connective-tissue collagen in meat, an
important factor in its tenderness, and the
source of gelatin (pp. 130, 597).
Protein Folds The other influence on protein
structure is the side groups of its amino acids.
Because the protein chain is so long, it can