UNE Biochemistry Midterm Exam
Questions and Answers
How do most enzymes reduce the activation energy needed to move a reaction
forward? - Answers -Providing an active site most complementary the transition state
An enzyme has a mutation within the substrate binding of the coenzyme needed for
covalent catalysis. Which of the following is likely to result as a consequence of this
mutation? - Answers -The enzyme will not be able to form the transition state complex
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? - Answers -The presence of
quaternary structure in hemoglobin
Cleavage of fructose 1,6-bisphosphate to dihydroxy and glyceraldehyde 3-phosphate is
achieved by what class of enzymes? - Answers -Lyase
Domains are common structural elements that retain a particular function within the
protein. Which of the following is an example of a protein domain? - Answers -An
arrangement of beta strands connected to alpha helices (BaBaB)
Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the
following amino acids would not facilitate this type of catalysis? - Answers -Valine
Which of the following proteins is likely to have quaternary structure? - Answers -A
multimeric protein that contains multiple peptide chains
What of the following best describes a protein domain? - Answers -A relatively large
pattern a three-dimensional structure that is recognized across many proteins
Movement of ammonia from an amino acid to an a-keto acid involved a family of
enzymes best categorized as which of the following? - Answers -Tranferases
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 a-helix structure to an aggregate of
mostly B-sheets. This change in protein structure (leading to disease) is best attributed
to changes in which of the following? - Answers -Folding of the secondary structures
, Chymotropsin is a protease that cleaves peptide bonds. It is characterized as which of
the following classes of enzymes? - Answers -Hydrolases
Which of the following best describes tertiary structure? - Answers -Interactions
between single amino acids adjacent to one another
Hemoglobin has the ability to display cooperative binding while myoglobin does not
display this binding pattern. Which of the following differences between the two proteins
accounts for the difference in binding kinetics? - Answers -The presence of quaternary
structure in hemoglobin
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? -
Answers -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? - Answers -The enzyme will not be able to form the
transition state complex
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? - Answers -The rate of the reaction is likely to
decrease as the pH is out of optimal catalytic range
Which of the following best describes an enzyme inhibitor that increases the Km but
does not change the Vmax? - Answers -A competitive inhibitor
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? - Answers -Increase DNA: histone association
In the image below the blue line indicates enzyme kinetics with no inhibitor present.
Based on this information which of the following is true? - Answers -The green line
shows enzyme kinetics with the addition of a noncompetitive inhibitor
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? - Answers -Feedback inhibition
Which of the following is an example of enzyme regulation through covalent
modification? - Answers -Phosphorylation of muscle glycogen phosphorylase
Under low energy conditions, AMP will bind to phosphofructokinase 1 and glycogen
phophorylase at a site unique to the active site. This enhances the activity of these
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