Transcript Buffers

BC 367
Review Questions for Exam 1
250 mL of 1.0 M HCl is added to 1.0 L of a 1.0
M acetic acid/sodium acetate buffer at pH 4.76
(pKa = 4.76). What is pH of the final solution?
A. 5.24
B. 4.28
C. 4.55
D. 3.86
E. 4.76 (this is a buffer!)
What effect would hypoventilating (slow and
shallow breathing) have on the blood?
a) No change in blood pH.
b) A decrease in [CO2], causing an increase in [H+]
and decrease in pH.
c) An increase in [CO2], causing an increase in [H+]
and decrease in pH.
d) A decrease in [CO2], causing an increase in [H+]
and increase in pH.
e) An increase in [CO2], causing a decrease in [H+]
and increase in pH.
This titration curve is for what amino acid?
http://cti.itc.virginia.edu/~cmg/Demo/markPka/markPkaApplet.html
a) Arg
b) His
c) Leu
d) Cys
e) Glu
You want to separate a mixture of three
hypothetical proteins, all of which repeat certain
amino acid sequences. The sequences and their
masses are below. What should you use to best
separate these proteins?
A. Gel filtration column
B. CM-sephadex column run at pH 7
C. Gel electrophoresis
Protein
Mr
D. Affinity chromatography
Repeating
amino acid
sequence
Protein 1
Val-Lys-Arg
22 900
Protein 2
Gln-Phe-Gly
59 000
Protein 3
Asp-Leu-Glu
23 100
E. Paper chromatography
Which of these peptides would be least
soluble in a solution at a pH of 5.5?
a) (Arg-Gly)2
b) (Met-Asp-Val)3
c) (Phe-Lys)5
d) (Asn-Phe-Gln)3
e) (Ala-Pro-Ile)3
A peptide was exposed to two separate enzyme digests to yield the
fragments shown below. At physiological pH, what is the approximate
net charge of the last five residues prior to digestion?
Chymotrypsin
Arg-Trp
Asp
Lys-Arg-Met-Phe
Lys-Leu-Phe
A) -1
B) 0
C) +1
D) +2
E) Not enough information
Trypsin
Trp-Lys
Met-Phe-Asp
Leu-Phe-Arg
Lys
Arg
Which one of the following peptides is most likely to adopt
an alpha helix?
A) Arg-Thr-Ile-Val-Tyr-Phe-Trp-Ile
B) Arg-Ala-Trp-Glu-Gly-Arg-Arg-Asp
C) Ala-Glu-Leu-Ala-Lys-Ala-Met-Asp
D) Val-Thr-Gly-Pro-Thr-Asn-Pro-Arg
E) None of these peptide will be alpha helical because they all contain lefthanded amino acids.
Protein A contains 1000 amino acids and
has a unit evolutionary period of 6 million
years. Protein A has an ortholog in another
species that diverged 12 million years ago.
How many amino acids differ between the
sequences of the two orthologs of protein
A?
A. 200
B. 100
C. 20
D. 10
E. 2