Biochemistry USMLE practice questions
and answers 2024
A 67-year-old man has a restricted diet that includes no fresh citrus fruits or leafy green
vegetables. His teeth are loose and his gums bleed easily. This patient's disorder most
likely results from a defect in collagen synthesis that involves which of the following
amino acids? - CORRECT ANSWERS-Hydroxyproline
A 60 year old man who lives alone came to the clinic with complaints of bleeding gums.
After investigation he was found to have vitamin C deficiency, which is required for
which stage of collagen biosynthesis? - CORRECT ANSWERS-Hydroxylation of proline
and lysine residues, you need vitamin C during this stage.
27-year-old woman with epilepsy has been taking phenytoin to control her seizures. She
is now pregnant, and her physician is considering changing her medication to prevent
potential bleeding episodes in the infant. What biochemical activity might be deficient in
the infant if her medication is continued? - CORRECT ANSWERS-γ-Carboxylation of
glutamate
20 year old medical student met an accident and suffered from multiple injuries all over
the body with the bone fracture. Your surgeon colleague prefers to supplement patients
with ascorbic acid after surgery. The doctor trying to optimize which one of the following
process? - CORRECT ANSWERS-The hydroxylation of proline in tropocollagen=helps
with the healing of the bone fracture.
Which amino acid is most responsible for the destabilization of an alpha helical
structure: - CORRECT ANSWERS-proline
The pH of plasma is normally kept between 7.2 and 7.4. What is the most important
blood buffer? - CORRECT ANSWERS-imidazole group of histidine
Which amino acid will be positively charged at neutral pH? - CORRECT ANSWERS-
Arginine
What will the net charge of this peptide be (Valine,Proline,isoleucine, leucine,glycine) -
CORRECT ANSWERS-0
All amino acids found in humans are optically active, name them: - CORRECT
ANSWERS-D-glycine
L-glycine: except
L-lysine
L-arginine
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, reduce gastric HCL secretion) deactivates the H/K ATPase in gastric parietal cells by
forming a covalent bond with the ATPase. The bond was not susceptible to acid or base
catalyzed hydrolysis. The drug probly contains which functional group that would be
critical for its action? - CORRECT ANSWERS-Reactive sulfhydryl group
If a certain amino acid has a pk1 of 4 and a pk2 of 6, what is the pH of the zwitterion (pI)
- CORRECT ANSWERS-5
In a neutral polar amino acid which of the following is occuring as pH is increasing
towards pk1? - CORRECT ANSWERS-Deprotonation of carbonyl group
What is the isoelectric point of alanine? - CORRECT ANSWERS-pH at which the net
charge is zero
pH at which both the carboxyl group and amino group are ionized
pH at which the amino acid exists in zwitterionic form
This short peptide is used as an important cofactor and required for the integrity of rbc
membranes - CORRECT ANSWERS-glutathione
A quality shared by all peptide bonds - CORRECT ANSWERS-Single bond character:
NOT
Rigid and planar
trans-configuration
Uncharged, but polar
In aqueous solution, the side chains of a non-polar amino acid will tend to cluster
where? - CORRECT ANSWERS-Interior of protein
How is secondary structure stabilized - CORRECT ANSWERS-Hydrogen bond
During electrophoresis, the restricted hb-S protein band will move towards which
relative position? - CORRECT ANSWERS-Closer to the anode than Hb-C
In antiparallel beta- pleated sheets what is the relative position of the N and C terminal
amino acids - CORRECT ANSWERS-N and C terminal amino acids are closest to each
other
A 65 yr. old banker was taken to his family doctor by his son for showing mood
changes, minor memory loss, and decreased motor skills. A potential explaination for
his symptoms is which of the following proteins? - CORRECT ANSWERS-Misfolded
form of a normal protein
Which similar property will the normal prion protein share w/ an infectious prion protein?
- CORRECT ANSWERS-Primary structure
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and answers 2024
A 67-year-old man has a restricted diet that includes no fresh citrus fruits or leafy green
vegetables. His teeth are loose and his gums bleed easily. This patient's disorder most
likely results from a defect in collagen synthesis that involves which of the following
amino acids? - CORRECT ANSWERS-Hydroxyproline
A 60 year old man who lives alone came to the clinic with complaints of bleeding gums.
After investigation he was found to have vitamin C deficiency, which is required for
which stage of collagen biosynthesis? - CORRECT ANSWERS-Hydroxylation of proline
and lysine residues, you need vitamin C during this stage.
27-year-old woman with epilepsy has been taking phenytoin to control her seizures. She
is now pregnant, and her physician is considering changing her medication to prevent
potential bleeding episodes in the infant. What biochemical activity might be deficient in
the infant if her medication is continued? - CORRECT ANSWERS-γ-Carboxylation of
glutamate
20 year old medical student met an accident and suffered from multiple injuries all over
the body with the bone fracture. Your surgeon colleague prefers to supplement patients
with ascorbic acid after surgery. The doctor trying to optimize which one of the following
process? - CORRECT ANSWERS-The hydroxylation of proline in tropocollagen=helps
with the healing of the bone fracture.
Which amino acid is most responsible for the destabilization of an alpha helical
structure: - CORRECT ANSWERS-proline
The pH of plasma is normally kept between 7.2 and 7.4. What is the most important
blood buffer? - CORRECT ANSWERS-imidazole group of histidine
Which amino acid will be positively charged at neutral pH? - CORRECT ANSWERS-
Arginine
What will the net charge of this peptide be (Valine,Proline,isoleucine, leucine,glycine) -
CORRECT ANSWERS-0
All amino acids found in humans are optically active, name them: - CORRECT
ANSWERS-D-glycine
L-glycine: except
L-lysine
L-arginine
1|Page
, reduce gastric HCL secretion) deactivates the H/K ATPase in gastric parietal cells by
forming a covalent bond with the ATPase. The bond was not susceptible to acid or base
catalyzed hydrolysis. The drug probly contains which functional group that would be
critical for its action? - CORRECT ANSWERS-Reactive sulfhydryl group
If a certain amino acid has a pk1 of 4 and a pk2 of 6, what is the pH of the zwitterion (pI)
- CORRECT ANSWERS-5
In a neutral polar amino acid which of the following is occuring as pH is increasing
towards pk1? - CORRECT ANSWERS-Deprotonation of carbonyl group
What is the isoelectric point of alanine? - CORRECT ANSWERS-pH at which the net
charge is zero
pH at which both the carboxyl group and amino group are ionized
pH at which the amino acid exists in zwitterionic form
This short peptide is used as an important cofactor and required for the integrity of rbc
membranes - CORRECT ANSWERS-glutathione
A quality shared by all peptide bonds - CORRECT ANSWERS-Single bond character:
NOT
Rigid and planar
trans-configuration
Uncharged, but polar
In aqueous solution, the side chains of a non-polar amino acid will tend to cluster
where? - CORRECT ANSWERS-Interior of protein
How is secondary structure stabilized - CORRECT ANSWERS-Hydrogen bond
During electrophoresis, the restricted hb-S protein band will move towards which
relative position? - CORRECT ANSWERS-Closer to the anode than Hb-C
In antiparallel beta- pleated sheets what is the relative position of the N and C terminal
amino acids - CORRECT ANSWERS-N and C terminal amino acids are closest to each
other
A 65 yr. old banker was taken to his family doctor by his son for showing mood
changes, minor memory loss, and decreased motor skills. A potential explaination for
his symptoms is which of the following proteins? - CORRECT ANSWERS-Misfolded
form of a normal protein
Which similar property will the normal prion protein share w/ an infectious prion protein?
- CORRECT ANSWERS-Primary structure
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