EXAM 2 BIOC 384
An enzyme has a single active site at which it can bind and hydrolyze either X
or Y; however, the enzyme cannot bind X and Y at the same time. Answer the
following questions regarding the Km and the Vmax of this enzyme. Choose a
total of three answers, one for each question A, B, and C.
A) Will the apparent Km for X be affect if Y is present in the reaction mixture?
B) Will Vmax for X be affected if Y is present in the reaction mixture?
C) Is it possible for Vmax and Vmax/Km to show a different dependence on
pH? - ANSWERS-A. yes
B. no
C. yes
An enzyme undergoes a mutation that causes it to lose the ability to be regulated
via phosphorylation. Which of the following mutations may lead to this loss of
regulation? Assume that the overall structure is not altered by the mutation. -
ANSWERS-Tyr --> Phe
Procathepsin B is a lysosomal protease that is first translated as a proenzyme.
On autocleavage it is fully activated. Procathepsin B is - ANSWERS-a zymogen
Consider the reaction above. For the uncatalyzed reaction, Kf(uncatalyzed) = 5
x 20^-4 s-1 and Keq is 2.5 x 10^2. For the same reaction in the presence of an
enzyme, Kf(catalyzed) is 5 x 10^5 s-1.
What is Kr(catalyzed)? - ANSWERS-2 x 10^3 s-1
,What is the rate enhancement as a result of the presence of an enzyme if the
uncatalyzed rate of the reaction is 1.2 mc005-1.jpg 102 mmol/sec and the
catalyzed rate is 2.4 mc005-2.jpg 104 mmol/sec? - ANSWERS-200
Although most protein sequencing is now done by mass spectrometry (MS),
Edman degradation (ED) is useful if large amounts of a protein can be obtained
even if from an uncharacterized species. Answer the True/False questions
regarding methods used to sequence a polypeptide fragment: - ANSWERS-
False
False
True
True
False
X-ray crystallography (XRC) and NMR spectroscopy provide three dimensional
structural information about the position of atoms in a purified protein. Name
one advantage and one disadvantage of each technique with regard to high
resolution protein structures. - ANSWERS-XRC/adv - large proteins, dvg -
requires crystals
NMR/adv - soluble protein, dvg - small proteins
Protein-specific antibodies are useful experimental tools in biochemistry.
Choose the one statement below that most correctly describes these biochemical
reagents. - ANSWERS-Polyclonal antibodies are a heterogenous mixture of
antibodies that recognize epitopes on an antigen.
Match each representative protein with the most correct specific major protein
functional class.
Record your answer in the order of a, b, c, d, and e, by choosing the numbers 1,
2, 3, 4, and 5.
Cell signaling
, Metabolic enzyme
Genomic caretaker
Structural protein
Transport protein - ANSWERS-4, 1, 5, 3, 2
G protein coupled reactor, Malate dehydrogenase, RNA polymerase, Tubulin,
Na+/K+ ATPase
Which statement most accurately describes the structure and function of O2
transport proteins. - ANSWERS-Hemoglobin is a tetramer that can bind BPG
and O2 whereas myoglobin binds O2 but cannot bind BPG.
Answer the following questions about the graph shown at the right. -
ANSWERS-(1) protein A
(2) protein A
(3) protein B
(4) protein A
(5) protein B
(6) protein A
In one type of hemoglobin mutant the amino acid change eliminates a hydrogen
bond that normally stabilizes the R state. Would you expect this mutant
hemoglobin to have a higher or lower O2 affinity compared to the normal
protein and why? - ANSWERS-Lower O2 affinity because the R-T equilibrium
would be mostly shifted to the T state.
What is the effect of pH on O2 binding in the lungs compared to the tissues and
why? - ANSWERS-The correct answer is not given.
An enzyme has a single active site at which it can bind and hydrolyze either X
or Y; however, the enzyme cannot bind X and Y at the same time. Answer the
following questions regarding the Km and the Vmax of this enzyme. Choose a
total of three answers, one for each question A, B, and C.
A) Will the apparent Km for X be affect if Y is present in the reaction mixture?
B) Will Vmax for X be affected if Y is present in the reaction mixture?
C) Is it possible for Vmax and Vmax/Km to show a different dependence on
pH? - ANSWERS-A. yes
B. no
C. yes
An enzyme undergoes a mutation that causes it to lose the ability to be regulated
via phosphorylation. Which of the following mutations may lead to this loss of
regulation? Assume that the overall structure is not altered by the mutation. -
ANSWERS-Tyr --> Phe
Procathepsin B is a lysosomal protease that is first translated as a proenzyme.
On autocleavage it is fully activated. Procathepsin B is - ANSWERS-a zymogen
Consider the reaction above. For the uncatalyzed reaction, Kf(uncatalyzed) = 5
x 20^-4 s-1 and Keq is 2.5 x 10^2. For the same reaction in the presence of an
enzyme, Kf(catalyzed) is 5 x 10^5 s-1.
What is Kr(catalyzed)? - ANSWERS-2 x 10^3 s-1
,What is the rate enhancement as a result of the presence of an enzyme if the
uncatalyzed rate of the reaction is 1.2 mc005-1.jpg 102 mmol/sec and the
catalyzed rate is 2.4 mc005-2.jpg 104 mmol/sec? - ANSWERS-200
Although most protein sequencing is now done by mass spectrometry (MS),
Edman degradation (ED) is useful if large amounts of a protein can be obtained
even if from an uncharacterized species. Answer the True/False questions
regarding methods used to sequence a polypeptide fragment: - ANSWERS-
False
False
True
True
False
X-ray crystallography (XRC) and NMR spectroscopy provide three dimensional
structural information about the position of atoms in a purified protein. Name
one advantage and one disadvantage of each technique with regard to high
resolution protein structures. - ANSWERS-XRC/adv - large proteins, dvg -
requires crystals
NMR/adv - soluble protein, dvg - small proteins
Protein-specific antibodies are useful experimental tools in biochemistry.
Choose the one statement below that most correctly describes these biochemical
reagents. - ANSWERS-Polyclonal antibodies are a heterogenous mixture of
antibodies that recognize epitopes on an antigen.
Match each representative protein with the most correct specific major protein
functional class.
Record your answer in the order of a, b, c, d, and e, by choosing the numbers 1,
2, 3, 4, and 5.
Cell signaling
, Metabolic enzyme
Genomic caretaker
Structural protein
Transport protein - ANSWERS-4, 1, 5, 3, 2
G protein coupled reactor, Malate dehydrogenase, RNA polymerase, Tubulin,
Na+/K+ ATPase
Which statement most accurately describes the structure and function of O2
transport proteins. - ANSWERS-Hemoglobin is a tetramer that can bind BPG
and O2 whereas myoglobin binds O2 but cannot bind BPG.
Answer the following questions about the graph shown at the right. -
ANSWERS-(1) protein A
(2) protein A
(3) protein B
(4) protein A
(5) protein B
(6) protein A
In one type of hemoglobin mutant the amino acid change eliminates a hydrogen
bond that normally stabilizes the R state. Would you expect this mutant
hemoglobin to have a higher or lower O2 affinity compared to the normal
protein and why? - ANSWERS-Lower O2 affinity because the R-T equilibrium
would be mostly shifted to the T state.
What is the effect of pH on O2 binding in the lungs compared to the tissues and
why? - ANSWERS-The correct answer is not given.
