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UNE BIOCHEMISTRY MIDTERM EXAM QUESTIONS AND ANSWERS
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UNE BIOCHEMISTRY MIDTERM EXAM QUESTIONS AND ANSWERS
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UNE BIOCHEMISTRY MIDTERM EXAMQUESTIONS AND ANSWERS
How do most enzymes reduce the activation energy needed to move a reaction forward?
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?
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?
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?
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?
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?
Valine
Which of the following proteins is likely to have quaternary structure?
A multimeric protein that contains multiple peptide chains
What of the following best describes a protein domain?
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?
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?
Folding of the secondary structures
Chymotropsin is a protease that cleaves peptide bonds. It is characterized as which of the
following classes of enzymes?
Hydrolases
Which of the following best describes tertiary structure?
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?
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?
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?
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?
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?
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?
, 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?
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?
Feedback inhibition
Which of the following is an example of enzyme regulation through covalent modification?
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 enzymes.
This is an example of which of the following types of enzyme regulation?
Allosteric activation
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?
Phosphorylation is a common covalent modification that can have various impacts on activity
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?
Competitive inhibitors often look like the substrate and compete in the active site for binding
Use the figure below to compare the activities of glucokinase and hexokinase. Based on this
information, which of the following is a true statement?
Glucokinase has a higher Km than hexokinase
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?
The enzyme will require a lower substrate concentration to reach 1/2 Vmax
Complex II (Succinate Q-reductase) is not considered to be part of the process of oxidative
phosphorylation because it is unable to do which of the following activities?
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