Problem Set 1
MBB 222 – Molecular Biology and Biochemistry
First Name: _____________________________________________________
Last Name: _____________________________________________________
Student Number: __________________________________
Tutorial Day and Time: ___________________________________________
Total marks for Problem Set =32 marks
Your score = _______
Problem set is due on Friday, September 20 , 2013 in class.
Hand in your problem set to your Teaching Assistant for marking in class.
Write your answers in pen. Answers written in pencil will not be accepted.
Write CLEARLY! Zero marks will be given to questions with answers that are not legible!!
For questions that require a numerical value as an answer (i.e., concentration, pH, ratio, equilibrium
constant, etc.), please have the value UNDERLINED so that Teaching Assistants can locate the answer
This problem set is worth 2% towards your final mark in the course.
1. Which of the following statements is true? Circle one answer! (2 marks)
A. Dimethyl ether and ethanol are constitutional isomers of each other.
B. The chemical structures of 2-propanol and 4-octanol contain a chiral carbon.
C. Amide, hydroxyl and carboxyl are examples of functional groups found in the chemical structure
of Tylenol .
D. 2-chlorobutane is an example of a chemical structure that is achiral.
E. All the above statements are false.
The correct answer is A (2 marks for selecting correct statement)
The chemical structures of 2-propanol and 4-octanol contain a chiral carbon. (FALSE...2-
propanol does not contain a chiral carbon)
Amide, hydroxyl and carboxyl are examples of functional groups found in the chemical structure
of Tylenol . (FALSE...no carboxyl group in Tylenol )
1 | P a g e 2-chlorobutane is an example of a chemical structure that is achiral. (FALSE...2-chlorobutane has
no plane of symmetry, and therefore is chiral!)
2. Assign (R) or (S) configurations to the indicated * stereocenters in the following molecules (0.5 mark for
correctly identifying each configuration x 4 = 2 marks in total):
(a) S (b) S (c) R (d) S (0.5 mark for each correct answer)
3. The (R,R) isomer of Ritalin is used to treat attention deficit hyperactivity disorder. The (S,S) isomer is
an antidepressant. Identify the two chiral carbons in the structure below (make sure you clearly circle the
two chiral carbons). Is the structure below the (R,R) or the (S,S) isomer? (1 mark for correctly identifying
both chiral carbons + 1 mark for correctly identifying the isomer = 2 marks in total)
The isomer is (S,S) (1 mark for isomer)
2 | P a g e The two chiral carbons are: (0.5 mark for identifying each correct chiral carbon)
4. In the blanks provided, determine if the pair or chemical structures as either a constitutional isomer,
diastereomer or enantiomer (0.5 mark for each correct answer x 4 = 2 marks total):
3 | P a g e ANSWER
(a) Constitutional isomer – 3-methylpentane and hexane (0.5 mark)
(b) Diastereomer – cis-2-butene and trans-2-butene (0.5 mark)
(c) Enantiomer – (2R,3R)-tartaric acid and (2S,3S)-tartaric acid (0.5 mark)
(d) Diastereomer – (2S,3S)-tartaric acid and (2R,3S)-tartaric acid (0.5 mark)
5. Write the conjugate base for the following acids (0.5 mark for each correct answer x 4 = 2 marks total):
(a) HC 2 4 ___________________
(b) HSO 3 ___________________
(c) H2PO 4- ___________________
(d) HPO 2- ___________________
(a) HC 2 4 C 2 42-(0.5 mark)
(b) HSO 3- SO 3 2-.5 mark)
(c) H2PO 4 HPO 4 (0.5 mark)
(d) HPO 4- PO 43-(0.5 mark)
6. Rank the following molecules from most polar to least polar. (1 mark for correct ranking)
(a) NH 3CH -CO2
(c) NH 3CH -CH2-CH 2COO 2
Ranking from most polar to least polar is: C>A>D>B (1 mark for correct ranking...NO PARTIAL
Dipole moment (μ=qx)
+ - + -
NH -3H -CH2-CH -2OO > 2H -CH -COO > H3S > C2l 2 4
Whole charges separated Whole charges Like Symmetrical (μ=0)
by largest distance separated H 2
(but smaller distance
4 | P a g e 7. Rank the following molecules from most soluble to least soluble in water. (1 mark for correct ranking)
CH – C – NH
(a) CH – C3 – O – CH2 3 (b) 3 2
CH - CH – C – H NH – C – NH
3 2 2 2
Ranking from most soluble to least soluble in water is: D>B>C>A (1 mark for correct ranking...NO
Structure D has 3 H-bond donors/acceptors > Structure B has 2 H-bond donors/acceptors > Structure C
has 1 H-bond acceptor > Structure A has 1 H-bond acceptor, but has extra CH 3
8. The H 2O /4PO 4 buffer system has a pa of 6.8. What is the ratio of monohydrogen phosphate to
dihydrogen phosphate in the urine at pH = 4.8? Make sure you show your work! (1 mark for correctly
showing work + 2 marks for correct ratio = 3 marks in total)
pH = pKa + log [HPO / 4 PO 2 4
4.8 = 6.8 + log [HPO 4H P2 ] 4-
-2 = log [HPO /H PO ] -
2- 4- 2 4
[HPO /4 PO 2 = 4/100 (2 marks for correct ratio + 1 mark for