Chemistry 223b Midterm, March 2008 Page 1
Please ensure that you have entered code 000 on your answer sheet.
1. Suppose Schrodinger owned a big, fluffy cat that appeared white under sunlight.
If the cat was placed in a room that was illuminated with only green light, what
colour would the cat appear?
2. Which one of the following molecules has the smallest HOMO-LUMO gap?
E) Chemistry 223b Midterm, March 2008 Page 2
3. The spectral data produced by a UV-visible spectrometer is typically a plot of…
A) Absorbance as a function of wavelength
B) Wavelength as a function of time
C) Fluorescence as a function of wavelength
D) Absorbance as a function of fluorescence
E) Fluorescence as a function of time
4. What is the non-radiative photophysical process indicated below?
E) Excitationalcooling Chemistry 223b Midterm, March 2008 Page 3
5. The coloured form of the acid-base indicator phenolphthalein has two negative
charges. Which one of A – E is NOT a correct resonance structure of the rest?
A) O O B) O O
C) O D) O
E) O O
O Chemistry 223b Midterm, March 2008 Page 4
6. Which part of the cell uses an adenine residue to catalyze a nucleophilic acyl
substitution reaction between a mixed anhydride and an amino group?
A) None of the other answers are correct
7. Which two of the following are most likely to be found in the outer membrane of
Gram-( ) bacteria?
A) 2 and 3
B) 2 and 4
C) 1 and 2
D) 3 and 4
E) 1 and 3 Chemistry 223b Midterm, March 2008 Page 5
8. What is the predominant form of lysine at pH 12?
H2NC C O H2NC C OH
A) CH2 B) CH2
H NH C O HN CH C O
C) 2 D) 2
H3NC C OH
NH3 Chemistry 223b Midterm, March 2008 Page 6
9. Which one of the following statements ab-amino acids is NOT correct?
A) The pKa of the COOH group is higher than that of a normal carboxylic acid
due to stabilization of the conjugate base by thegroup
B) They are amphoteric
C) Most natural amino acids have the L configuration and are S
D) Amino acids are very soluble in acidic and basic solutions
E) At neutral pH, they are usually not very soluble in water
10. The tertiary structure of a protein refers to…
A) The way the protein folds over on itself
B) The arrangement of the peptide into aeet
C) The arrangement of the peptide into a -helix
D) The interaction of protein subunits
E) The presence of heme molecules bound to protein
11. Which one of A – E is least likely to be involved in the mechanism of the following
H /H 2
RCOOH + H NR'
R NH 2' 3
O OH HO OH
A) B) C)
R NH R' R NH R'
2 R NHR' 2
HO OH 2 OH
R NHR' Chemistry 223b Midterm, March 2008 Page 7
12. Which one of the following statements is NOT correct regarding the use of HPLC
for the determination of amino acid composition?
A) The amino acids are combined with ninhydrin to form purple complexes,
which are then separated by the chromatography column.
B) A sample of hydrolyzed protein is injected into the HPLC.
C) The identity of the amino acid can be determined by the retention time.
D) The relative quantities of the amino acids can be determined by comparing
the relative areas of the absorption peaks.
E) Molecules that adhere strongly to the stationary phase of the chromatography
column will have a higher retention time.
13. Which one of A – E is least likely to be involved in the mechanism of the following
NR" H /H O O
+ R" NH 2
R R' R R'
NH 2R'' NHR'' HO NH R''
A) B) C) 2
R R' R R'
D) E) H 2 NHR''
R R' R R' Chemistry 223b Midterm, March 2008 Page 8
14. Which of A – E is/are proper resonance structure(s) of Ruhemann’s Purple,
which is formed when two equivalents of ninhydrin react with an amino acid?
OH O O O
O O O O
OH O O O
O O O O
A) 2 and 5
B) 5 only
C) 1 and 4 only
D) 3 and 5 only
E) 2 and 3 only Chemistry 223b Midterm, March 2008 Page 9
15. Sanger analysis of an unknown peptide gave one equivalent of the molecule on
the left and two equivalents of the one on the right.
O2N NH COOH
O 2 NO 2 H2N
What could the peptide be?
3. Gly-Pro-L ys-Lys-Phe-Val
A) 2 and 5 only
B) 1 and 4 only
C) 1 and 3 only
E) None of them Chemistry 223b Midterm, March 2008 Page 10
16. The compound below was the first phenylthiohydantoin to be isolated from an
Edman degradation. What could the peptide be?
3. Gly-Pr o-Cys-Phe
A) 3 only
B) 2 only
C) 1 and 4 only
D) 2 and 3 only
E) 1 and 3 only
17. What does the term graduated acid lability best refer to?
A) The different sensitivities of acid derivatives towards destruction by acid.
B) The varying abilities of acids to protonate leaving groups.
C) The volumes occupied by the same mass of different amino acids are large
enough to be measured using a graduated pipette.
D) The relationship between acid strength and conjugate-base stability
E) The presence of many different functional groups of varying pKa values in an
enzyme active site. Chemistry 223b Midterm, March 2008 Page 11
18. Which of A – E is/are least likely to be involved in the following reaction?
N C N
+ H 2R'
R OH R NHR'
N NC N O
H R O
1 2 3
A) 2 only
B) 4 only
C) 3 only
D) 1 and 5 only
E) None (all of 1 – 5 are involved) Chemistry 223b Midterm, March 2008 Page 12
19. Consider the following solid-phase peptide synthesis. Assume that each DCC
coupling step proceeds in 90% yield. Assume that all of the other steps proceed
in 100% yield. What will be the approximate distribution of products?
+ DCC, then rinse
O O NH-BOC
O O H
1. TFA, then rinse
2. 3t, then rinse
+ DCC, then rinse
HBr / HOAc O O
HO N N NH
A) Val-Ala-Leu (81%), Val-Ala (9%), Val-Leu (9%), Val (1%)
B) Val-Ala-Leu (90%), Val-Ala (5%), Val-Leu (4%), Val (1%)
C) Val-Ala-Leu (81%), Val-Ala-Ala (9%), Val-Leu-Leu (9%), Val (1%)
D) Val-Ala-Leu (90%), Val (10%)
E) Val-Ala-Leu (73%), Val-Ala (18%), Val-Leu (8%), Val (1%) Chemistry 223b Midterm, March 2008 Page 13
20. What is the purpose of the BOC protecting group?
A) To decrease the nucleophilicity of the amino group
B) To increase the nucleophilicity of the amino group
C) To decrease the electrophilicity of the amino group
D) To increase the electrophilicity of the amino group
E) To convert the amino group into a better leaving group
21. Which statement does NOT correctly describe the current state of the
chymotrypsin-substrate complex below and the next mechanistic step that
His Ser N
N N O
R 2 N
Asp R 1