UNE Biochemistry Midterm Study Questions & Answers
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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 alpha helical structure to an aggregate of mostly beta sheets. This
change in protein structure (leading to disease) is best attributed to
changes in which of the following? Correct Ans - folding of the
secondary structures
Which of the following is the best description of primary protein structure?
Correct Ans - a newly synthesized strand of amino acids
How do most enzymes reduce the activation energy needed to move a
reaction forward? Correct Ans - providing an active site most
complementary the transition state
Movement of ammonia from an amino acid to an a-keto acid involves a
family of enzymes best categorized as which of the following? Correct
Ans - transferases
Hemoglobin has the ability to display cooperative binding while myoglobin
does not display this binding kinetic pattern. Which of the following
differences between the two proteins accounts for this difference in
binding kinetics? Correct Ans - the presence of quaternary
structure
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 Ans - increase in 2,3
bisphosphoglycerate (BPG)
An enzyme has a mutation within the substrate binding site that reduces
the binding of the coenzyme needed for covalent catalysis. Which of the
following is likely to result as a consequence of this mutation? Correct
Ans - the enzyme will not be able to form the transition state complex
, Chymotrypsin is a protease that cleaves peptide bonds. It is characterized
as which of the following classes of enzymes? Correct Ans -
hydrolases
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 Ans - the enzyme will require a lower
substrate concentration to reach 1/2 Vmax
Which of the following best describes an enzyme inhibitor that increases
the Km but does not change the Vmax? Correct Ans - a competitive
inhibitor
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 Iikely impact to the rate of the reaction? Correct
Ans - the rate of the reaction is likely to decrease as the pH is out of
optimal catalytic range
A new enzyme is discovered that increases in activity when it is
phosphorylated on an exposed tyrosine residue. Phosphorylation of this
amino acid is classified as which of the following? Correct Ans -
covalent modification
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 Ans - the green line shows enzyme kinetics with the addition of
a noncompetitive inhibitor
An example of enzyme activation by cleavage is best illustrated by which of
the following? Correct Ans - activation of chymotrypsinogen to
chymotrypsin
Use the figure below to compare the activities of glucokinase and
hexokinase. Based on this information, which of the following is a true
statement? Correct Ans - glucokinase has a higher Km than
hexokinase
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