BIOC384 Exam UPDATED ACTUAL
Exam Questions and CORRECT Answers
An estrogen-dependent breast cancer cell line is grown in a medium that contains estrogen. Cell
proliferation is monitored over time. In a separate experiment, the cell line is grown in a medium
that lacks estrogen but includes bisphenol A, a compound found in polycarbonate plastics. When
monitored, cell proliferation is higher than in the presence of estrogen. A possible explanation of
these results is that bisphenol A - CORRECT ANSWER - is an agonist of the estrogen
receptor
When ATCase is in the __________ state it indicates that ____________ is bound, and that
ATCase is ______________ regulated. - CORRECT ANSWER - T; CTP; down
How can an extracellular signal be amplified a million-fold inside a cell? Choose the ONE
correct answer. - CORRECT ANSWER - Activation of a single receptor can result in the
production of 100 second messengers. Each of these second messengers can activate an enzyme
that can act on 100 target enzymes. Each target enzyme can act on 100 other targets. 100 X 100
X 100 = 1,000,000
Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity
is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site
of the enzyme. Sarin gas is a(n) - CORRECT ANSWER - irreversible inhibitor
What characteristic is true for both RTKs and GPCRs? - CORRECT ANSWER - The
receptor undergoes a conformational change on activation.
Redox enzymes commonly use electron carrier coenzymes such as NAD+/NADH, FAD/FADH2.
Why are these coenzymes necessary? Choose the ONE correct answer. - CORRECT
ANSWER - Protein side chains are not chemically suited to reversibly bind electrons
under a broad range of conditions.
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. - CORRECT ANSWER - Tyr -->
Phe
Signaling activity of G proteins is controlled by GTPase activating proteins (GAPs) and Guanine
exchange factors (GEFs). What are the mechanisms by which GAPs and GEFs control G
proteins (GPs)? - CORRECT ANSWER - GAPs inhibit GPs by stimulating GTP
hydrolysis; GEFs activate GPs by stimulating GDP-GTP exchange.
Levels of diacylglycerol increase in a cell on binding of a ligand to a taste receptor. Which
trimeric G protein subunit is most likely to be bound to GTP? - CORRECT ANSWER -
Gqa
Which of the following pairs correctly matches the type of interaction observed between an
inhibitor and an enzyme with the type of inhibition? - CORRECT ANSWER - Hydrogen
bonding and reversible
A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the line
in the middle represents the enzyme activity in the absence of any allosteric effectors, then the
line to the __________ represents the enzyme in the __________ when bound to __________. -
CORRECT ANSWER - Right, T state, CTP
Procathepsin B is a lysosomal protease that is first translated as a proenzyme. On autocleavage it
is fully activated. Procathepsin B is - CORRECT ANSWER - Zymogen
Which of the following list includes ONLY first messengers? - CORRECT ANSWER -
Cortisol, insulin, and prostaglandins
A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The
activity of the enzyme is assessed before and after the chromatography. The enzyme has more
activity after the chromatography step. Which of the following is true? - CORRECT
ANSWER - The inhibitor is a reversible inhibitor
What is the appropriate order of the following steps?
, A. Glutamine binding to uridylyltransferase
B. Adenylation of glutamine synthetase
C. Deuridylation of glutamine synthetase adenylyltransferase - CORRECT ANSWER - A,
C, B
Consider the reaction shown below
(A) Identify the kind of chemical catalysis
(B) Identify which of the amino acids can act as X in the reaction
Choose ONE correct answer for each (A and B). - CORRECT ANSWER - A) acid base
catalysis, B) HIS.
Which of the following are characteristics of allosteric enzymes like ATCase? Choose the
THREE that apply. Allosteric enzymes:
may have binding sites for regulatory molecules that are separate from active sites.
interconvert between a more active form and less active form.
tend to have a sigmoidal (S-shaped) curve of V0 vs. [S]. - CORRECT ANSWER - may
have binding sites for regulatory molecules that are separate from active sites.
interconvert between a more active form and less active form.
tend to have a sigmoidal (S-shaped) curve of V0 vs. [S].
If protein kinase A is activated in a liver cell in response to glucagon binding to the B 2-
adrenergic receptor, which of the following will result? - CORRECT ANSWER -
Glycogen degradation will be turned on.
Which of the following are characteristics of allosteric enzymes such as aspartate
transcarbamoylase. There are only three correct answers.
a. Often have a sigmoidal (S-shaped) curve of Vo versus [S].
b. Conform to Michaelis-Menten kinetics.
c. Are usually small single subunit proteins.
d. Undergo conformational changes between the R and T state.
Exam Questions and CORRECT Answers
An estrogen-dependent breast cancer cell line is grown in a medium that contains estrogen. Cell
proliferation is monitored over time. In a separate experiment, the cell line is grown in a medium
that lacks estrogen but includes bisphenol A, a compound found in polycarbonate plastics. When
monitored, cell proliferation is higher than in the presence of estrogen. A possible explanation of
these results is that bisphenol A - CORRECT ANSWER - is an agonist of the estrogen
receptor
When ATCase is in the __________ state it indicates that ____________ is bound, and that
ATCase is ______________ regulated. - CORRECT ANSWER - T; CTP; down
How can an extracellular signal be amplified a million-fold inside a cell? Choose the ONE
correct answer. - CORRECT ANSWER - Activation of a single receptor can result in the
production of 100 second messengers. Each of these second messengers can activate an enzyme
that can act on 100 target enzymes. Each target enzyme can act on 100 other targets. 100 X 100
X 100 = 1,000,000
Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity
is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site
of the enzyme. Sarin gas is a(n) - CORRECT ANSWER - irreversible inhibitor
What characteristic is true for both RTKs and GPCRs? - CORRECT ANSWER - The
receptor undergoes a conformational change on activation.
Redox enzymes commonly use electron carrier coenzymes such as NAD+/NADH, FAD/FADH2.
Why are these coenzymes necessary? Choose the ONE correct answer. - CORRECT
ANSWER - Protein side chains are not chemically suited to reversibly bind electrons
under a broad range of conditions.
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. - CORRECT ANSWER - Tyr -->
Phe
Signaling activity of G proteins is controlled by GTPase activating proteins (GAPs) and Guanine
exchange factors (GEFs). What are the mechanisms by which GAPs and GEFs control G
proteins (GPs)? - CORRECT ANSWER - GAPs inhibit GPs by stimulating GTP
hydrolysis; GEFs activate GPs by stimulating GDP-GTP exchange.
Levels of diacylglycerol increase in a cell on binding of a ligand to a taste receptor. Which
trimeric G protein subunit is most likely to be bound to GTP? - CORRECT ANSWER -
Gqa
Which of the following pairs correctly matches the type of interaction observed between an
inhibitor and an enzyme with the type of inhibition? - CORRECT ANSWER - Hydrogen
bonding and reversible
A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the line
in the middle represents the enzyme activity in the absence of any allosteric effectors, then the
line to the __________ represents the enzyme in the __________ when bound to __________. -
CORRECT ANSWER - Right, T state, CTP
Procathepsin B is a lysosomal protease that is first translated as a proenzyme. On autocleavage it
is fully activated. Procathepsin B is - CORRECT ANSWER - Zymogen
Which of the following list includes ONLY first messengers? - CORRECT ANSWER -
Cortisol, insulin, and prostaglandins
A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The
activity of the enzyme is assessed before and after the chromatography. The enzyme has more
activity after the chromatography step. Which of the following is true? - CORRECT
ANSWER - The inhibitor is a reversible inhibitor
What is the appropriate order of the following steps?
, A. Glutamine binding to uridylyltransferase
B. Adenylation of glutamine synthetase
C. Deuridylation of glutamine synthetase adenylyltransferase - CORRECT ANSWER - A,
C, B
Consider the reaction shown below
(A) Identify the kind of chemical catalysis
(B) Identify which of the amino acids can act as X in the reaction
Choose ONE correct answer for each (A and B). - CORRECT ANSWER - A) acid base
catalysis, B) HIS.
Which of the following are characteristics of allosteric enzymes like ATCase? Choose the
THREE that apply. Allosteric enzymes:
may have binding sites for regulatory molecules that are separate from active sites.
interconvert between a more active form and less active form.
tend to have a sigmoidal (S-shaped) curve of V0 vs. [S]. - CORRECT ANSWER - may
have binding sites for regulatory molecules that are separate from active sites.
interconvert between a more active form and less active form.
tend to have a sigmoidal (S-shaped) curve of V0 vs. [S].
If protein kinase A is activated in a liver cell in response to glucagon binding to the B 2-
adrenergic receptor, which of the following will result? - CORRECT ANSWER -
Glycogen degradation will be turned on.
Which of the following are characteristics of allosteric enzymes such as aspartate
transcarbamoylase. There are only three correct answers.
a. Often have a sigmoidal (S-shaped) curve of Vo versus [S].
b. Conform to Michaelis-Menten kinetics.
c. Are usually small single subunit proteins.
d. Undergo conformational changes between the R and T state.
