On Food and Cooking

bend back on itself and bring together amino
acids that are some distance along the chain
from each other. Amino acids with similar
side groups can then bond to each other in
various ways, including via hydrogen bonds,
van der Waals bonds, ionic bonds (p. 813),
and strong covalent bonds (especially between
sulfur atoms). This bonding is what gives a
particular protein molecule the characteristic
shape that allows it to carry out its particular
job. The weak, temporary nature of the
hydrogen and hydrophobic bonds allows it to
change its shape as it works. The overall
shape of a protein can range from a long,
extended, mostly helical molecule with a few
kinks or loops, to compact, elaborately folded
molecules that are called “globular” proteins.
Collagen is an example of a helical protein,
and the various proteins in eggs are mainly
globular.