Download Chemistry 326 Name_____________________ Fall 2009 Check

Chemistry 326
Fall 2009
Name_____________________
Check Section:
Tuesday ______
Wednesday_____
Thursday ______
Exam 2
If I cannot read your writing I will not grade the answer and it will be
assigned “0” points.
1. Answer true or false:(20)
_____a. PLP/PMP act through a Schiff base mechanism.
_____b. NAD contains a sugar alcohol.
_____c. Lipoamide can exist in an oxidized or reduced form of the disulfide bridge.
_____d. NAD works in redox reactions that involve alkyl groups.
_____e. Tetrohydrofolate carries the most oxidized form of carbon.
_____f. CoA, NAD, FAD all contain nucleotides in their structures.
_____g. FAD accepts or donates reducing equivalents in the form of a hydride ion.
_____h. Biotin contains cobalt.
_____i. TPP is involved in redox reactions.
_____j. Biotin and lipoic acid must be covalently bound to the enzyme to function.
_____k. Enzymes are generally comparable in size to the substrates on which they act.
_____l. Enzymes can be classed on the basis of the types of reactions they catalyze.
_____m. Enzymes lower the energy of activation for reactions they catalyze.
_____n. At low substrate concentrations, the initial rate is first order.
_____o. Zymogens are examples of covalent modification.
_____p. The KM of an enzyme-catalyzed reaction is independent of the substrate used.
_____q. The Vmax value for a substrate is altered by a competitive inhibitor.
_____r. The KM value for a substrate is not altered by a competitive inhibitor.
_____s. Isoenzymes work on different substrates.
_____t. An ApoProtein is a non-protein moeity.
2. Regarding enzyme kinetics: (25pts)
a. What is the significance of the term KM?(4pts)
b. What are the units for KM?(4pts)
c. What is a competitive inhibitor?(4pts)
d. What is a Lineweaver -Burk plot? Sketch such a plot and label
all relevant details. Include in the plot the competitive
and non-competitive curves. (8pts)
e. If the substrate concentration is expressed in mol/L and the
reaction rate in micromoles of product per minute, what are the
units of Vmax and KM?(5pts)
3. Which of the reactions listed below are catalyzed by an isomerase, lyase,
hydrolase, transferase, ligase or oxidoreductase? (10pts)
__________a. D-glycine → L-glycine
__________b. Polysaccharide + HOH → n-monosaccharides
__________c. Fructose + ATP → fructose-6-phosphate + ADP
__________d. CH3C(O)COOH → CH3CHO + CO2
__________e. 3-phosphoglyceraldehyde + NAD+ → 3-phosphoglycerate + NADH
4. Answer true or false: (10pts)
_____a. The tertiary structure of myoglobin is similar to that of a subunit of
hemoglobin.
_____b. The quaternary structure of myoglobin is similar to that of a subunit of
hemoglobin.
_____c. Myoglobin has one binding site for oxygen per molecule.
_____d. Hemoglobin has one binding site for oxygen per heme.
_____e. BPG lowers the oxygen affinity for oxygen for both myoglobin
and hemoglobin.
5. Fetal Hemoglobin (HbF) contains serine in place of the cationic histidine
of the β chains of adult hemoglobin (HbA). This histidine residue faces the
central cavity between the β chains. (10pts)
a. Why does 2,3BPG bind more tightly to deoxy HbA than to deoxy HbF?
b. How does the decreased affinity of HbF for 2,3BPG affect the
affinity of HbF for oxygen?
6. How does the reaction of carbon dioxide with water help explain the Bohr
effect? Include the equation for the formation of the bicarbonate ion from
CO2 and water, and explain the effects H+ and CO2 on hemoglobin
oxygenation. (10pts)
7. Reduction potentials for a pathogenic bacterium are: (15pts)
___________________________________________________________
Oxidant
Reductant
Electrons transferred
Eo'
_______________________________________________________________________________________________
1. NAD+
NADH
2
-0.32
2. Flavoprotein b
Flavoprotein b
2
-0.62
(oxidized)
(reduced)
3. Cytochrome C(+3) Cytochrome C (+2)
2
+0.22
4. Ferroprotein
Ferroprotein
2
+0.85
(oxidized)
(reduced)
5. Flavoprotein a
Flavoprotein a
2
+0.77
(oxidized)
(reduced)
___________________________________________________________
a. Predict the sequence of the carriers in the electron transport chain. Use
the numbers before each oxidant.
b. How many molecules of ATP can be generated under standard conditions
when a pair of electrons is transported along the pathway? (F=23.06Kcal
and +7.3Kcal/mol is required to drive the synthesis of one ATP under
standard conditions)
c. Is oxygen the terminal electron acceptor? Explain.
(1/2O2 + 2H+ + 2e- → H2O
E0'=0.816v)