BCH 4053 Final Exam V3 | BCH 4053 Biochemistry I | Actual Q&A with
Rationale (BCH4053 Final Exam) | University of Central Florida
1. Which of the following amino acids is considered achiral because its R-group is a hydrogen
atom?
A. Alanine
B. Valine
C. Proline
D. Glycine
Answer: D
Explanation: Glycine is unique among the 20 standard amino acids because its alpha-
carbon is bonded to two hydrogen atoms. This symmetry makes the molecule achiral and
not optically active. Consequently, glycine can occupy more conformational space in a
polypeptide chain than other amino acids.
2. In the Michaelis-Menten model, the Michaelis constant (Km) is defined as:
A. The substrate concentration at which the reaction velocity is half of Vmax
B. The maximum rate at which the enzyme can catalyze the reaction
C. The total concentration of the enzyme in the system
D. The equilibrium constant for the breakdown of the ES complex
Answer: A
Explanation: The Michaelis constant (Km) represents the substrate concentration at which
the enzyme achieves half of its maximum velocity. It provides an inverse measure of the
enzyme’s affinity for its substrate under specific conditions. A low Km value indicates high
affinity, meaning the enzyme reaches half-saturation at a low substrate concentration.
3. Which type of inhibition can be overcome by increasing the substrate concentration?
A. Non-competitive inhibition
B. Irreversible inhibition
C. Uncompetitive inhibition
D. Competitive inhibition
Answer: D
,Explanation: In competitive inhibition, the inhibitor competes directly with the substrate
for the active site of the enzyme. By increasing the substrate concentration, the substrate is
more likely to bind to the active site than the inhibitor, effectively reaching the same Vmax.
However, the apparent Km increases because more substrate is required to achieve half-
saturation.
4. The secondary structure of a protein is primarily stabilized by:
A. Disulfide bonds between cysteine residues
B. Hydrophobic interactions between nonpolar side chains
C. Ionic interactions between oppositely charged R-groups
D. Hydrogen bonds between the backbone carbonyl and amide groups
Answer: D
Explanation: Secondary structure elements such as alpha-helices and beta-sheets are
formed through regular patterns of hydrogen bonding. These bonds occur specifically
between the carbonyl oxygen of one peptide bond and the amide hydrogen of another. This
stabilization is independent of the specific side chains of the amino acids involved.
5. Which molecule acts as a negative heterotropic effector of hemoglobin, reducing its oxygen
affinity?
A. Carbon monoxide (CO)
B. Nitric oxide (NO)
C. 2,3-Bisphosphoglycerate (2,3-BPG)
D. Molecular oxygen (O2)
Answer: C
Explanation: 2,3-Bisphosphoglycerate (2,3-BPG) binds to the central cavity of the
hemoglobin tetramer and stabilizes the T-state (deoxy state). This binding significantly
reduces hemoglobin’s affinity for oxygen, allowing for more efficient oxygen release in
peripheral tissues. Without 2,3-BPG, hemoglobin would bind oxygen too tightly to release it
effectively under physiological conditions.
6. The peptide bond is characterized by:
A. Full rotation around the C-N bond
B. Partial double-bond character due to resonance
C. A non-planar geometry
D. Susceptibility to spontaneous hydrolysis in neutral water
Answer: B
, Explanation: The peptide bond exhibits resonance between the carbonyl and the amide
nitrogen, resulting in about 40% double-bond character. This resonance makes the C-N
bond shorter and prevents free rotation, constraining the peptide group into a rigid, planar
configuration. This planarity is a fundamental constraint in the folding of protein structures
into specific shapes.
7. Which of the following sugars is a non-reducing disaccharide?
A. Lactose
B. Sucrose
C. Cellobiose
D. Maltose
Answer: B
Explanation: Sucrose consists of glucose and fructose linked via an alpha-1,beta-2
glycosidic bond between their anomeric carbons. Because both anomeric carbons are
involved in the bond, neither can open into a linear aldehyde or ketone form. Therefore,
sucrose does not react with Fehling’s or Benedict’s reagents and is classified as non-
reducing.
8. The ‘Bohr Effect’ refers to the:
A. Decrease in oxygen affinity of hemoglobin as pH decreases
B. Cooperative binding of oxygen to the heme group
C. Effect of pH on the absorption spectrum of hemoglobin
D. Increase in oxygen affinity as carbon dioxide levels drop
Answer: A
Explanation: The Bohr Effect describes the regulation of oxygen binding by hemoglobin in
response to changes in pH and CO2 concentration. As metabolic activity increases, the
concentration of H+ and CO2 rises, which stabilizes the T-state of hemoglobin. This causes
the oxygen dissociation curve to shift to the right, facilitating the release of oxygen where it
is most needed.
9. Which of the following is the primary driving force for the folding of globular proteins?
A. Hydrogen bonding between side chains
B. The hydrophobic effect
C. Van der Waals interactions
D. Formation of disulfide bridges
Answer: B
Rationale (BCH4053 Final Exam) | University of Central Florida
1. Which of the following amino acids is considered achiral because its R-group is a hydrogen
atom?
A. Alanine
B. Valine
C. Proline
D. Glycine
Answer: D
Explanation: Glycine is unique among the 20 standard amino acids because its alpha-
carbon is bonded to two hydrogen atoms. This symmetry makes the molecule achiral and
not optically active. Consequently, glycine can occupy more conformational space in a
polypeptide chain than other amino acids.
2. In the Michaelis-Menten model, the Michaelis constant (Km) is defined as:
A. The substrate concentration at which the reaction velocity is half of Vmax
B. The maximum rate at which the enzyme can catalyze the reaction
C. The total concentration of the enzyme in the system
D. The equilibrium constant for the breakdown of the ES complex
Answer: A
Explanation: The Michaelis constant (Km) represents the substrate concentration at which
the enzyme achieves half of its maximum velocity. It provides an inverse measure of the
enzyme’s affinity for its substrate under specific conditions. A low Km value indicates high
affinity, meaning the enzyme reaches half-saturation at a low substrate concentration.
3. Which type of inhibition can be overcome by increasing the substrate concentration?
A. Non-competitive inhibition
B. Irreversible inhibition
C. Uncompetitive inhibition
D. Competitive inhibition
Answer: D
,Explanation: In competitive inhibition, the inhibitor competes directly with the substrate
for the active site of the enzyme. By increasing the substrate concentration, the substrate is
more likely to bind to the active site than the inhibitor, effectively reaching the same Vmax.
However, the apparent Km increases because more substrate is required to achieve half-
saturation.
4. The secondary structure of a protein is primarily stabilized by:
A. Disulfide bonds between cysteine residues
B. Hydrophobic interactions between nonpolar side chains
C. Ionic interactions between oppositely charged R-groups
D. Hydrogen bonds between the backbone carbonyl and amide groups
Answer: D
Explanation: Secondary structure elements such as alpha-helices and beta-sheets are
formed through regular patterns of hydrogen bonding. These bonds occur specifically
between the carbonyl oxygen of one peptide bond and the amide hydrogen of another. This
stabilization is independent of the specific side chains of the amino acids involved.
5. Which molecule acts as a negative heterotropic effector of hemoglobin, reducing its oxygen
affinity?
A. Carbon monoxide (CO)
B. Nitric oxide (NO)
C. 2,3-Bisphosphoglycerate (2,3-BPG)
D. Molecular oxygen (O2)
Answer: C
Explanation: 2,3-Bisphosphoglycerate (2,3-BPG) binds to the central cavity of the
hemoglobin tetramer and stabilizes the T-state (deoxy state). This binding significantly
reduces hemoglobin’s affinity for oxygen, allowing for more efficient oxygen release in
peripheral tissues. Without 2,3-BPG, hemoglobin would bind oxygen too tightly to release it
effectively under physiological conditions.
6. The peptide bond is characterized by:
A. Full rotation around the C-N bond
B. Partial double-bond character due to resonance
C. A non-planar geometry
D. Susceptibility to spontaneous hydrolysis in neutral water
Answer: B
, Explanation: The peptide bond exhibits resonance between the carbonyl and the amide
nitrogen, resulting in about 40% double-bond character. This resonance makes the C-N
bond shorter and prevents free rotation, constraining the peptide group into a rigid, planar
configuration. This planarity is a fundamental constraint in the folding of protein structures
into specific shapes.
7. Which of the following sugars is a non-reducing disaccharide?
A. Lactose
B. Sucrose
C. Cellobiose
D. Maltose
Answer: B
Explanation: Sucrose consists of glucose and fructose linked via an alpha-1,beta-2
glycosidic bond between their anomeric carbons. Because both anomeric carbons are
involved in the bond, neither can open into a linear aldehyde or ketone form. Therefore,
sucrose does not react with Fehling’s or Benedict’s reagents and is classified as non-
reducing.
8. The ‘Bohr Effect’ refers to the:
A. Decrease in oxygen affinity of hemoglobin as pH decreases
B. Cooperative binding of oxygen to the heme group
C. Effect of pH on the absorption spectrum of hemoglobin
D. Increase in oxygen affinity as carbon dioxide levels drop
Answer: A
Explanation: The Bohr Effect describes the regulation of oxygen binding by hemoglobin in
response to changes in pH and CO2 concentration. As metabolic activity increases, the
concentration of H+ and CO2 rises, which stabilizes the T-state of hemoglobin. This causes
the oxygen dissociation curve to shift to the right, facilitating the release of oxygen where it
is most needed.
9. Which of the following is the primary driving force for the folding of globular proteins?
A. Hydrogen bonding between side chains
B. The hydrophobic effect
C. Van der Waals interactions
D. Formation of disulfide bridges
Answer: B
