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UNE Biochemistry Midterm FULL –Questions &Answers
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UNE Biochemistry Midterm FULL –Questions &AnswersHow do most enzymes reduce the activation energy needed to move a
reaction forward? Correct Ans - 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? Correct Ans - 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? Correct Ans - 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? Correct Ans -
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? Correct Ans - 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?
Correct Ans - Valine
Which of the following proteins is likely to have quaternary structure?
Correct Ans - A multimeric protein that contains multiple peptide
chains
What of the following best describes a protein domain? Correct Ans -
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? Correct
Ans - 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? Correct Ans - Folding of the secondary
structures
Chymotropsin is a protease that cleaves peptide bonds. It is characterized
as which of the following classes of enzymes? Correct Ans -
Hydrolases
Which of the following best describes tertiary structure? Correct Ans -
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?
Correct Ans - 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? 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
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 Ans -
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? Correct Ans - 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? Correct Ans
- 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?
Correct Ans - 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? Correct
Ans - Feedback inhibition
Which of the following is an example of enzyme regulation through
covalent modification? Correct Ans - 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? Correct Ans - 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? Correct Ans -
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? Correct Ans - 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? Correct Ans - 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? Correct Ans - 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? Correct Ans - Pump protons from the
mitochondrial matrix to the inner membrane space
Which of the following components of the electron transport chain is not
bound to the mitochondrial membrane? Correct Ans - CoQ of
cytochrome C
The glycerophosphate shuttle is the major shuttle of most tissues. Which of
the following best describes the transfer of electrons by this shuttle?
Correct Ans - Electrons are directly transferred from glycerol 3-
phosphate to an FAD containing glycerol phosphate dehydrogenase
The last cytochrome in the ETC, cytochrome oxidase, passes electrons to
O2, Cytochrome C oxidase is able to do this because it has which the
following characteristics? Correct Ans - A lower Km for oxygen
than hemoglobin
Which of the following would be consistent with an exergonic reaction?
Correct Ans - Delta G0 would be negative
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