Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

The peptide bond attaches the [?]
of the amine group of one amino acid to
the carbon of the carboxyl group of
another amino acid liberating one
molecule of [?]. So the –R groups do
not participate in that bond.