Download Test 1

BCH 4053
June 2, 2000
(10)
1.
HOUR TEST 1
NAME_____________________
Carbonic Acid in solution is an equilibrium mixture of H2 CO3 and
dissolved CO2 . If its standard state is taken a 1 M for the sum of both
forms, then pK1 for the following reaction is 6.1:
H2 CO3 (total) € H+ +
HCO3 -
(a) Calculate the [HCO3 -]/[H2 CO3 (total)] ratio in blood at pH 7.4.
Page
Points
1
2
3
4
____
____
____
____
Total
______
(b) Normally buffers have their best buffering capacity at their pK. Yet bicarbonate buffer
is a very good buffer at pH 7.4, even better than at its pK of 6.1. Explain why.
2.
(10)
Draw the structure of the following peptide, showing all dissociable functional groups in
their fully protonated form, and indicate the approximate pK of each of the dissociable
functional groups:
(a) Lys.Cys.Arg.Tyr.Glu
(1)
(b) What is the charge on the fully protonated form of the peptide?
(1)
(c) What is the charge on the fully unprotonated form of the peptide?
(1)
(d) What is the approximate pI of the peptide?
(1)
(e) What is the net charge on the peptide at pH 6.0?
BCH 4053 --Hour Test 1
Page 2
Name________________________
(12)
3.
Formic acid has a pK of 3.75. How many mL of 0.1 M NaOH must be added to 100 mL of
0.05 M formic acid to make a buffer solution with a pH of 4.25?
(20)
4.
Identify the following amino acids by giving the name, the three letter abbreviation, and
the one letter abbreviation. The number of amino acids in each category is given in
parenthesis.
Category
Contains a sulfur atom (2)
Name
Abbreviations
_______________________________________________________
_______________________________________________________
Absorbs UV light
above 250 nm (3)
_______________________________________________________
_______________________________________________________
_______________________________________________________
Contains an amide group
in the side chain (2)
_______________________________________________________
_______________________________________________________
Contains an imidazole
group in the side chain (1)
_______________________________________________________
Contains a guanidinium
group in the side chain (1)
_______________________________________________________
An alpha imino acid (1)
_______________________________________________________
BCH 4053 --Hour Test 1
5.
Page 3
Name________________________
The standard free energy change for ATP hydrolysis is –30.5 kJ/mol and for glycerol-3phosphate hydrolysis is –9.2 kJ/mol.
(a) Calculate ∆Go ' for the glycerokinase reaction:
(4)
ATP
+
glycerol
€
ADP
+
glycerol-3-phosphate
(4)
(b) Calculate ∆G for the reaction if [glycerol-3-P] = 10 mM, [glycerol] = 0.10 mM,
[ATP] = 5.0 mM, and [ADP] = 1.0 mM. (Temperature = 37 o C; R = 8.314 J/mol-K)
(4)
(c) Calculate Keq' for this reaction at 37 o C.
(5)
6.
List five unusual properties of water resulting from its hydrogen bonded structure.
(5)
7.
Draw a diagram to show how water will interact with an amphipathic molecule such as
sodium palmitate. What is the name for the structure assumed by the sodium palmitate in
water?
BCH 4053 --Hour Test 1
For Questions 8 to 14, put a check mark by the
best answer. (14 points)
8. Of the following weak chemical interactions,
which is the weakest?
____ hydrogen bonding
____ hydrophobic bonding
____ induced dipole-induced dipole attraction
____ dipole-dipole attraction
____ coulombic attraction
9. Hydrophobic bonding between non-polar
groups is primarily a result of:
____ dispersion forces of attraction between the
groups.
____ electrostatic attraction between the groups.
____ an entropy increase in water when the
groups associate.
____ an entropy decrease in water when the
groups associate.
10. Which of the following compounds has the
highest ∆Go ' of hydrolysis?
____ ATP
____ Pyrophosphate
____ glucose-1-phosphate
____ phosphoenolpyruvate
11. A closed system
____ exchanges matter and heat with
surroundings.
____ exchanges only heat with surroundings.
____ exchanges heat and work with
surroundings.
____ exchanges nothing with surroundings.
12. A process with a negative entropy change
and a positive enthalpy change will be
____ spontaneous at all temperatures.
____ non-spontaneous at all temperatures.
____ spontaneous at high temperatures only.
____ spontaneous at low temperatures only.
13. Which amino acids have two chiral carbons?
____ lysine and arginine
____ threonine and glutamine
____ leucine and isoleucine
____ threonine and isoleucine
____ proline and methionine
Page 4
Name________________________
14. A cation exchange column
____ has a positively charged functional group
and binds cations.
____ has a negatively charged functional group
and binds anions.
____ has a positively charged functional group
and binds anions.
____ has a negatively charged functional group
and binds cations.
For Questions 15 and 16, put a check by all
correct answers (8 points)
15. Peptide A has a pI of 5.5. Peptide B has a pI
of 8.5. Which of the following is true?
____ Both peptides will bind to an anion
exchange resin at pH 7.
____ Both peptides will bind to a cation
exchange resin at pH 7.
____ Peptide A will bind to a cation exchange
resin at pH 7.
____ Peptide B will bind to a cation exchange
resin at pH 7.
____ Peptide A will bind to an anion exchange
resin at pH 7.
____ Peptide B will bind to an anion exchange
resin at pH 7.
____ Both peptides will bind to an anion
exchange resin at pH 4.
____ Both peptides will bind to a cation
exchange resin at pH 4.
16. With respect to proteins, which of the
following statements are true?
____ Proteins are polymers of sugar residues.
____ Amino acids are building blocks of
proteins.
____ Peptide bonds are amide bonds.
____ The primary structure refers to the overall
three dimensional structure of the protein.
____ The secondary structure refers to the
ordered repeating structure along the
peptide backbone.
____ The quaternary structure refers to the
orientation around the peptide bond.
____ The alpha helix is an example of secondary
structure.
____ Globular proteins fold up so that the nonpolar amino acid side chains are on the
interior.