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Which statement about polypeptides in cells is wrong?
a. they are a polymer of γ-amino acids linked by peptide bonds
b. the sequence of amino acids is determined by instructions on the cell's DNA
c. they have an -NH3+ group at one end of the polymer
d. they have a -COO- group at one end of the polymer
e. they are called proteins if they fold into a specific shape - Answer ✅a
A 27-year-old firefighter is brought to the emergency room after being exposed to smoke during
a training exercise. He looks ill and has labored breathing. He is clutching his head and exhibits
an altered mental status. On examination, you note that he appears red, and his pulse oximetry
reads 100%. You suspect carbon monoxide toxicity. What is TRUE about the oxygen saturation
curve during carbon monoxide poisoning?
a) the oxygen saturation curve is shifted to the left
b) the oxygen saturation curve is shifted to the right
c) the effect of carbon monoxide on hemoglobin is similar to that of having increased levels of
2,3 bisphosphoglycerate
d) the effect of carbon monoxide on hemoglobin is similar to that of a low pH state
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,e) the effect of carbon monoxide on hemoglobin is similar to that of an increased temperature
state - Answer ✅a
An example of irreversible regulation of enzyme activities is:
a. phosphorylation by protein kinases
b. allosteric regulation by substrates
c. dissociation of subunits into oligomeric enzymes
d. inhibition by competitive inhibitors
e. proteolytic conversion of digestive enzymes - Answer ✅e
The denaturation of a globular protein causes
a. loss of primary structure
b. loss secondary structure
c. loss of tertiary structure
d. a and c are correct
e. b and c are correct - Answer ✅e
Which of the following methods is commonly used to estimate the size of the subunits of a
protein?
a. isoelectric focusing
b. sodium dodecylsulfate polyacrylamide gel electrophoresis
c. amino acid analysis
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,d. ion exchange chromatography
e. salting out from solution - Answer ✅b
The pI for an amino acid is the:
a. pH at which an amino acid is electrically neutral
b. pKa value of the functional groups attached to the alpha-carbon
c. net pKa value for the ionizable side chains
d. same for all but one of the twenty amino acids
e. ratio of the number of oxygen atoms to carbon atoms in the amino acid - Answer ✅a
Allopurinol is used in the treatment of gout because of its ability makes to inhibit xanthine
oxidase. This inhibition makes it impossible for the enzyme to degrade xanthine to
hypoxanthine, which reduces the synthesis of urate, the culprit of gout. Allopurinol works
through which one of the following mechanisms?
a. suicide inhibitum
b. noncompetitive inhibition
c. allosteric interaction with the enzyme that increases Vmax
d. feedback inhibition
e. subunit cooperativity - Answer ✅a
A 30-year-old woman presented with progressive shortness of breath. She denied the use of
cigarettes. A family history revealed that her sister had suffered from unexplained lung disease.
Which one of the following etiologies most likely explains this patient's pulmonary symptoms?
a. deficiency of proline hydroxylase
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, b. deficiency of α1-antitrypsin
c. deficiency in dietary vitamin C
d. decreased elastase activity
e. increased collagenase activity - Answer ✅b
ADH requires NAD+ for catalytic activity. In the reaction catalyzed by ADH, an alcohol is oxidized
to an aldehyde as NAD+ is reduced to NADH and dissociates from the enzyme. The NAD+ is
functioning as a (an):
a. apoenzyme
b. coenzyme-cosubstrate
c. coenzyme-prosthetic group
d. holoenzyme
e. heterotropic effector - Answer ✅b
Drugs that inhibit enzymes in a competitive manner will have which of the following effects on
the Michaelis-Menten equation derived parameters?
a. decrease both Vmax and Km
b. decrease Km but no effect on Vmax
c. decrease Vmax but no change on Km
d. increase Km but no change in Vmax
e. increase Vmax but no increase in Km - Answer ✅d
Glucose travels across the cell membrane on a transport protein. Hereditary deficiency of GLUT-
1, insulin-independent transporter, results in decreased glucose transport. Patients manifest
with intractable seizures in infancy and a developmental delay. GLUT-1 transporter is expressed
in which of the following cell types?
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