UNE CHEM 1005 Midterm Review
UPDATED Questions with CORRECT
Answers
An 𝛂-helical arrangment of amino acids is considered to be part of what level of protein
structure? - CORRECT ANSWER - secondary structure
Hemoglobin has the ability to display cooperative binding, while myoglobin does not display this
binding kinetic pattern. Which difference between the two proteins accounts for this difference in
binding kinetics? - CORRECT ANSWER - the presence of quaternary structure in
hemoglobin; cooperativity is a binding characteristic only displayed in proteins with a quaternary
structure
A 22y/o female presents to the emergency department with acute abdominal pain. She indicates
the pain came on rapidly in her mid-abdominal region. Laboratory tests indicate elevated levels
of amylase. This result would indicate a dysfunction with which organ? - CORRECT
ANSWER - Pancreas
Cleavage of fructose 1, 6-bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate
involves the breaking of a carbon-carbon bond through a process other than oxidation or
hydrolysis. This is achieved by what class of enzymes? - CORRECT ANSWER - Lyase
Which of the following best describes tertiary structure? - CORRECT ANSWER -
Interactions between α-helices and β sheets to form a domain
Which of the following best describes a protein domain? - CORRECT ANSWER -A
section of a protein structure sufficient to perform a particular chemical or physical task
A 19-year-old boy is diagnosed with Creutzfeldt-Jakob Disease which is caused by the
introduction of an amyloid fold in the disease-causing protein. The introduction of this fold
causes the protein to transition from a primarily α-helical structure to an aggregate of mostly β-
sheets. This change in protein structure (leading to disease) is best attributed to changes in which
of the following? - CORRECT ANSWER - folding of the secondary structures
,Chymotrypsin is a protease that cleaves peptide bonds. It is characterized as which of the
following classes of enzymes? - CORRECT ANSWER - hydrolase
α-helices and β-sheets are primarily stabilized by which of the following interactions? -
CORRECT ANSWER - hydrogen bonding
Changes in the physiological variables listed below can alter the affinity of hemoglobin for
oxygen. Which of the following will lower the affinity of hemoglobin for oxygen? - CORRECT
ANSWER - increase in 2,3 bisphosphoglycerate (BPG)
Activity of an enzyme is increased when the enzyme is phosphorylated on an exposed tyrosine
residue. Phosphorylation of this AA is classified as? - CORRECT ANSWER - Covalent
modification--phosphorylation to an enzyme that can increase/decrease activity of an enzyme
Covalent catalysis is used by many enzymes to cleave peptide bonds. All of the following AA
side chains EXCEPT _____ will help reaction? - CORRECT ANSWER - Tyrosine,
histidine and methionine; NOT valine--nonpolar AA that lacks a nucleophile to facilitate the
generation of a catalyst-substrate covalent bond
If a mutation is made within the active site of an enzyme resulting in an increase in Km, which of
the following will be true with respect to the enzyme kinetics? - CORRECT ANSWER -
the enzyme will require a higher substrate concentration to reach 1/2 Vmax
what are the metabolic consequences of changes to the ubiquitin-proteasome system? -
CORRECT ANSWER - increases protein ubiquitination, would lead to increase in protein
degradation --> decrease in product production OR decrease in protein degradation, leading to
accomulation of the enzyme or protein --> INCREASE in product production
Protein Z requires phosphorylation at an exposed tyrosine residue for activity. If we modify this
tyrosine to a glycine, what impact does this have on the activity of protein Z? - CORRECT
ANSWER - Loss of the phosphorylation site will reduce the activity of the enzyme
(tyrosine has an exposed hydroxyl group that allows for phosphorylation and glycine doesn't, so
, modifying the enzyme to glycine takes away that available phosphorylation site. Loss of that site
will reduce the activity of the enzyme b/c can no longer be phosphorlyzed)
The following represents a series of reactions. As levels of B increase, this will decrease the
conversion of S3 to B. Which of the following best describes this type of regulation in a
biosynthetic pathway? - CORRECT ANSWER - feedback inhibition
In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on
this information which of the following is true? - CORRECT ANSWER - green line shows
enzyme kinetics with the addition of a noncompetitive inhibitor
Children with cystinosis have growth delay and both renal and ocular issues due to accumulation
of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor
that facilitates cysteine removal from the cell. An effective therapy has been administration of a
drug with a similar structure to cysteine. This therapy reflects the general principle that
competitive inhibitors typically resemble the structure of which of the following? - CORRECT
ANSWER - substrates or ligands that bind the active site
The association of DNA and histones can be modified by histone acetylation. A decrease in
histone acetylation will have which of the following impacts on the association of DNA and
histones? - CORRECT ANSWER - increase DNA: histone association
An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH
of 6.0. If acid is added to the environment reducing the pH to 3, what is the likely impact to the
rate of reaction? - CORRECT ANSWER - the rate of the reaction is likely to decrease as
the pH is out of optimal catalytic range
Which of the following is an example of enzyme regulation through covalent modification? -
CORRECT ANSWER - phosphorylation of muscle glycogen phosphorylase
If a mutation is made within the active site of an enzyme resulting in a decrease in Km, which of
the following will be true with respect to the enzyme kinetics? - CORRECT ANSWER -
the enzyme will require a lower substrate concentration to reach 1/2 Vmax
UPDATED Questions with CORRECT
Answers
An 𝛂-helical arrangment of amino acids is considered to be part of what level of protein
structure? - CORRECT ANSWER - secondary structure
Hemoglobin has the ability to display cooperative binding, while myoglobin does not display this
binding kinetic pattern. Which difference between the two proteins accounts for this difference in
binding kinetics? - CORRECT ANSWER - the presence of quaternary structure in
hemoglobin; cooperativity is a binding characteristic only displayed in proteins with a quaternary
structure
A 22y/o female presents to the emergency department with acute abdominal pain. She indicates
the pain came on rapidly in her mid-abdominal region. Laboratory tests indicate elevated levels
of amylase. This result would indicate a dysfunction with which organ? - CORRECT
ANSWER - Pancreas
Cleavage of fructose 1, 6-bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate
involves the breaking of a carbon-carbon bond through a process other than oxidation or
hydrolysis. This is achieved by what class of enzymes? - CORRECT ANSWER - Lyase
Which of the following best describes tertiary structure? - CORRECT ANSWER -
Interactions between α-helices and β sheets to form a domain
Which of the following best describes a protein domain? - CORRECT ANSWER -A
section of a protein structure sufficient to perform a particular chemical or physical task
A 19-year-old boy is diagnosed with Creutzfeldt-Jakob Disease which is caused by the
introduction of an amyloid fold in the disease-causing protein. The introduction of this fold
causes the protein to transition from a primarily α-helical structure to an aggregate of mostly β-
sheets. This change in protein structure (leading to disease) is best attributed to changes in which
of the following? - CORRECT ANSWER - folding of the secondary structures
,Chymotrypsin is a protease that cleaves peptide bonds. It is characterized as which of the
following classes of enzymes? - CORRECT ANSWER - hydrolase
α-helices and β-sheets are primarily stabilized by which of the following interactions? -
CORRECT ANSWER - hydrogen bonding
Changes in the physiological variables listed below can alter the affinity of hemoglobin for
oxygen. Which of the following will lower the affinity of hemoglobin for oxygen? - CORRECT
ANSWER - increase in 2,3 bisphosphoglycerate (BPG)
Activity of an enzyme is increased when the enzyme is phosphorylated on an exposed tyrosine
residue. Phosphorylation of this AA is classified as? - CORRECT ANSWER - Covalent
modification--phosphorylation to an enzyme that can increase/decrease activity of an enzyme
Covalent catalysis is used by many enzymes to cleave peptide bonds. All of the following AA
side chains EXCEPT _____ will help reaction? - CORRECT ANSWER - Tyrosine,
histidine and methionine; NOT valine--nonpolar AA that lacks a nucleophile to facilitate the
generation of a catalyst-substrate covalent bond
If a mutation is made within the active site of an enzyme resulting in an increase in Km, which of
the following will be true with respect to the enzyme kinetics? - CORRECT ANSWER -
the enzyme will require a higher substrate concentration to reach 1/2 Vmax
what are the metabolic consequences of changes to the ubiquitin-proteasome system? -
CORRECT ANSWER - increases protein ubiquitination, would lead to increase in protein
degradation --> decrease in product production OR decrease in protein degradation, leading to
accomulation of the enzyme or protein --> INCREASE in product production
Protein Z requires phosphorylation at an exposed tyrosine residue for activity. If we modify this
tyrosine to a glycine, what impact does this have on the activity of protein Z? - CORRECT
ANSWER - Loss of the phosphorylation site will reduce the activity of the enzyme
(tyrosine has an exposed hydroxyl group that allows for phosphorylation and glycine doesn't, so
, modifying the enzyme to glycine takes away that available phosphorylation site. Loss of that site
will reduce the activity of the enzyme b/c can no longer be phosphorlyzed)
The following represents a series of reactions. As levels of B increase, this will decrease the
conversion of S3 to B. Which of the following best describes this type of regulation in a
biosynthetic pathway? - CORRECT ANSWER - feedback inhibition
In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on
this information which of the following is true? - CORRECT ANSWER - green line shows
enzyme kinetics with the addition of a noncompetitive inhibitor
Children with cystinosis have growth delay and both renal and ocular issues due to accumulation
of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor
that facilitates cysteine removal from the cell. An effective therapy has been administration of a
drug with a similar structure to cysteine. This therapy reflects the general principle that
competitive inhibitors typically resemble the structure of which of the following? - CORRECT
ANSWER - substrates or ligands that bind the active site
The association of DNA and histones can be modified by histone acetylation. A decrease in
histone acetylation will have which of the following impacts on the association of DNA and
histones? - CORRECT ANSWER - increase DNA: histone association
An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH
of 6.0. If acid is added to the environment reducing the pH to 3, what is the likely impact to the
rate of reaction? - CORRECT ANSWER - the rate of the reaction is likely to decrease as
the pH is out of optimal catalytic range
Which of the following is an example of enzyme regulation through covalent modification? -
CORRECT ANSWER - phosphorylation of muscle glycogen phosphorylase
If a mutation is made within the active site of an enzyme resulting in a decrease in Km, which of
the following will be true with respect to the enzyme kinetics? - CORRECT ANSWER -
the enzyme will require a lower substrate concentration to reach 1/2 Vmax
