Download CHEM131 Quiz 5_AA

CHEM 131 – Spring 2011
Instructor: Maxi Boeckl
Your Name: _______________________
Quiz #3
1.
Draw the chemical structure of the following amino acids under the stated conditions. (4 pts)
a) Met under acidic conditions
b) Glutamate/glutamic acid under acidic conditions
c) Arg under physiological pH
d) Tyrosine under basic conditions
2. Draw the Fisher projection for the following amino acids (3 pts)
a. L-Lysine under basic conditions
b. D-Asparagine under physiological conditions
c. What is the net charge on the amino acids as drawn in part a. and b.
CHEM 131 – Spring 2011
Instructor: Maxi Boeckl
Your Name: _______________________
3. Draw the chemical structure for the following tripeptide: (3 pts)
a. Trp – Ile – Asp
b. Circle the acidic R group in the tirpeptide you drew in question part a and draw an arrow pointing out
each peptide bond.
4. Answer questions a-c about the Fisher projection of the amino acid shown on the right. (3 pts)
a) Briefly explain what is wrong with this Fisher projection.
CH3
HC
OH
H3N
H
COO
b) Considering the correct Fisher projection, is this an L- or D-amino acid?
c) Give the name of the amino acid drawn.
5. Circle the correct answer for each statement. (2 pts)
a. If hexokinase has an absolute specificity for D-sugars, will it be able to
recognize L-sugars as a substrate.
True
or
False
b. The driving force for the secondary structure of proteins is due to the
interactions of the R groups on different amino acid residues.
True
or
False
c. Fibrous proteins are easily transported through the body, since they have
mainly polar R groups on the outside.
True
or
False
d. Enzymes are highly efficient since they lower the activation energy of a
specific reaction.
True
or
False