Amino Acids and
Terminology (explain or defne; understand use oF terms)
side chain, R group, amino group, carboxyl group, aliphatic, aromatic, indole,
hydroxyl, thiol (sulfhydryl), imidazole, guanidino, isoelectric pH (pI), amide,
Learn the structure oF each oF the 20 amino acids, with its Full name and
DO THIS NOW – DON
T PUT IT O±±.
You won't have
to draw detailed structures of arginine or tryptophan, but you should be able to
recognize them, and draw the other structures, with the ionization reactions of
(see below). Draw the structure of a
and given the name or 3-letter or 1-letter abbreviation of any of the 20 amino
acids, draw its structure.
Are the 20 amino acids found in proteins the D- or L-isomers?
Name the functional groups on the side chains of Ala, Asn, Gln, Ser, Thr, Cys,
Tyr, Trp, Asp, Glu, His, Lys, Arg.
Know the Greek letters up through epsilon: alpha (
), beta (
), gamma (
), epsilon (
Classify any amino acid side chain into any of the following categories that
apply to it:
nonpolar, polar but uncharged (pH 7), acidic, or basic; ionizable or
non-ionizable; aliphatic or aromatic; S-containing; OH-containing.
amino acids fall into more than one of the above categories.)
For the 7 amino acids with ionizable side chains, be able to draw the side chain
structure in its weak acid and in its conjugate base form; know which form is
uncharged and which form is charged (and whether charged form is positively
Learning Objectives, continued
or negatively charged).
You do NOT need to memorize the pK
values For the
ionizable groups on the Free amino acids
, but given the pK
of an amino acid
functional group, be able to write the ionization reaction for that group.
Be able to sketch a titration curve (pH vs. equivalents of OH
added) for any of
the 20 amino acids and to explain what is happening to the molecule as the pH
increases between 1 and 14.
Be able to read pK
values off a titration curve and
explain what species (states of ionization) are present at each pK
and at each
integral equivalence point on the curve (1 equivalent of OH
equivalents added, etc.)
Given the pK
for an ionizable functional group and the pH of a solution, be able
to state qualitatively which ionic state of that group predominates at that pH
without the use of a calculator.
Be able to calculate (using the Henderson-Hasselbalch Equation or the de±nition
), with a non-programmable calculator, the percentage of a functional group
in a particular ionic state, given the pH of the solution and the pK
Given the percentage of the functional group in a particular
ionic state and the pK
of the group, be able to calculate the pH of the solution.