NEW 2025-2026 UNE BIOCHEMISTRY MIDTERM
QUESTIONS AND ANSWERS
How do most enzymes lower the activation energy required to propel a process
forward? - ANSWER Providing an active site that best complements the
transition stage.
An enzyme has a mutation that affects the substrate binding of the coenzyme
required for covalent catalysis. Which of the following is likely to occur as a
result of this mutation? - ANSWER The enzyme will be unable to generate the
transition state complex.
Myoglobin cannot exhibit cooperative binding, whereas haemoglobin does.
Which of the following changes between the two proteins explains the
difference in binding kinetics? - Answer: The presence of quaternary structure
in hemoglobin.
What enzyme class is responsible for the cleavage of fructose 1,6-bisphosphate
into dihydroxy and glyceraldehyde 3-phosphate? - Answer: Lyase.
Domains are common structural components that serve a specific function
inside a protein. Which of the following represents a protein domain? -
ANSWER A network of beta strands linked to alpha helices (BaBaB)
Many enzymes use covalent catalysis to cleave peptide bonds. Which of the
following amino acids would prevent this type of catalysis? - ANSWER
VALINE
Which of the following proteins is likely to have a quaternary structure? –
ANSWER: A multimeric protein with numerous peptide chains.
,Which of the following best defines a protein domain? - ANSWER A
comparatively large pattern is a three-dimensional structure that is recognized
by many proteins.
The movement of ammonia from an amino acid to an a-keto acid required a
family of enzymes known as which of the following? - Answer Transferases
A 19-year-old boy is diagnosed with Creutzfeldt-Jakob disease, which is caused
by the inclusion of an amyloid fold in the disease-causing protein. When this
fold is introduced, the protein's structure changes from mostly a-helix to
primarily B-sheet. This alteration in protein structure (which causes disease) is
most likely caused by changes in which of the following? - ANSWER The
folding of secondary structures
Chymotropsin is a protease that degrades peptide bonds. It belongs to which of
the following enzyme classes? - Answer: Hydrolases.
Which of the following best represents the tertiary structure? - ANSWER
Interactions between single amino acids next to each other
Myoglobin lacks the ability to exhibit cooperative binding, whereas hemoglobin
does. Which of the following changes between the two proteins explains the
difference in binding kinetics? - Answer: The presence of quaternary structure
in hemoglobin.
Changes in the physiological variables listed below can affect hemoglobin's
affinity for oxygen. Which of the following will diminish hemoglobin's affinity
for oxygen? - ANSWER Increase in 2, 3 bisphosphoglycerate (BPG)
, A mutation in an enzyme's substrate binding site lowers the binding of the
coenzyme required for covalent catalysis. Which of the following is likely to
occur as a result of this mutation? - ANSWER The enzyme will be unable to
generate the transition state complex.
An enzyme is involved in a general acid-base catalysis reaction that has an
optimum pH of 6.0. What is the likely effect of adding acid to the environment,
lowering the pH to 3, on the rate of reaction? - ANSWER The pace of the
reaction is expected to decrease since the pH is outside of the ideal catalytic
range.
Which of the following best defines an enzyme inhibitor that increases Km but
does not affect Vmax? - Answer: A competitive inhibitor.
Histone acetylation can alter DNA-histone interactions. Which of the following
effects will a decrease in histone acetylation have on the DNA-histone
interaction? - ANSWER: Increase DNA histone association.
In the figure below, the blue line represents enzyme kinetics with no inhibitor
present. Based on this knowledge, which of the following is correct? -
ANSWER The green line depicts enzyme kinetics after the presence of a
noncompetitive inhibitor.
The following is a series of reactions. As the level of B increases, the
conversion of S3 to B decreases. Which of the following best characterizes this
kind of regulation in a biosynthetic pathway? - ANSWER: Feedback inhibition.
Which of the following is an example of enzyme control by covalent
modification? - ANSWER: phosphorylation of muscle glycogen phosphorylase
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