I'm confused by what my microbiology teacher wants me to do with the following problem:
"Consider the following peptide:
gluamine-glutamic acid-aspartic acid-tryptophan, with lysine as the amino-terminal acid and tryptophan as the carboxy-terminal amino acid in the peptide.
Draw out the complete structural formula of the peptide and determine the overall ionic charge on the peptide at pH 7.0. Charge at acid pHs? Charge at alkaline pHs?"
Can someone help me figure out how to draw this structure and figure out the ionic charges?