Biochemistry C785 Midterm Study Guide Quiz 2026 |WGU
1. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets formed by hydrogen bonding between the backbone atoms?
A. Primary Structure
B. Tertiary Structure
C. Secondary Structure
D. Quaternary Structure
Answer: C
Rationale: Secondary structure refers to local folded structures that form within a
polypeptide due to interactions between atoms of the backbone (not the side chains),
specifically alpha-helices and beta-sheets.
2. In the context of enzyme kinetics, what happens to Vmax and Km in the
presence of a competitive inhibitor?
A. Vmax decreases, Km remains the same
B. Vmax increases, Km decreases
C. Both Vmax and Km decrease
D. Vmax remains the same, Km increases
Answer: D
Rationale: Competitive inhibitors compete with the substrate for the active site. Increasing
substrate concentration can overcome the inhibitor, so Vmax stays the same, but more
substrate is needed to reach half-maximal velocity, thus increasing Km.
,3. Which molecule serves as the primary direct donor of electrons to the
Electron Transport Chain (ETC) at Complex I?
A. FADH2
B. NADH
C. NADPH
D. ATP
Answer: B
Rationale: NADH donates its electrons to Complex I (NADH dehydrogenase), while FADH2
donates its electrons to Complex II.
4. Which part of an amino acid defines its chemical properties and classification
(e.g., polar, non-polar, acidic, basic)?
A. The amino group
B. The carboxyl group
C. The R-group (side chain)
D. The alpha carbon
Answer: C
Rationale: While all amino acids share the amino and carboxyl groups, it is the unique
chemical structure of the R-group (side chain) that determines the specific properties of
each amino acid.
5. What is the primary role of myoglobin in human physiology?
A. Storing oxygen in muscle cells for immediate use
B. Transporting oxygen from lungs to tissues
C. Transporting carbon dioxide to the lungs
D. Buffering the pH of the blood
Answer: A
Rationale: Myoglobin has a high affinity for oxygen and acts as a storage reservoir in
muscle tissue, whereas hemoglobin is responsible for systemic transport.
, 6. Which of the following describes the ‘Bohr Effect’ regarding hemoglobin?
A. High pH increases oxygen affinity
B. Low 2,3-BPG levels favor the T-state
C. High CO2 and low pH decrease oxygen affinity, favoring oxygen release
D. Increased temperature increases oxygen binding
Answer: C
Rationale: The Bohr Effect describes how hydrogen ions (low pH) and carbon dioxide
stabilize the T-state (deoxygenated) of hemoglobin, facilitating the release of oxygen in
metabolically active tissues.
7. In DNA replication, which enzyme is responsible for unwinding the double
helix at the replication fork?
A. Helicase
B. Ligase
C. DNA Polymerase III
D. Topoisomerase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of DNA for replication.
8. Which process results in the production of two pyruvates, two ATP (net), and
two NADH from one glucose molecule?
A. Glycolysis
B. Citric Acid Cycle
C. Gluconeogenesis
D. Oxidative Phosphorylation
Answer: A
Rationale: Glycolysis occurs in the cytosol and is the initial breakdown of glucose into two
pyruvate molecules, yielding a net of 2 ATP and 2 NADH.
1. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets formed by hydrogen bonding between the backbone atoms?
A. Primary Structure
B. Tertiary Structure
C. Secondary Structure
D. Quaternary Structure
Answer: C
Rationale: Secondary structure refers to local folded structures that form within a
polypeptide due to interactions between atoms of the backbone (not the side chains),
specifically alpha-helices and beta-sheets.
2. In the context of enzyme kinetics, what happens to Vmax and Km in the
presence of a competitive inhibitor?
A. Vmax decreases, Km remains the same
B. Vmax increases, Km decreases
C. Both Vmax and Km decrease
D. Vmax remains the same, Km increases
Answer: D
Rationale: Competitive inhibitors compete with the substrate for the active site. Increasing
substrate concentration can overcome the inhibitor, so Vmax stays the same, but more
substrate is needed to reach half-maximal velocity, thus increasing Km.
,3. Which molecule serves as the primary direct donor of electrons to the
Electron Transport Chain (ETC) at Complex I?
A. FADH2
B. NADH
C. NADPH
D. ATP
Answer: B
Rationale: NADH donates its electrons to Complex I (NADH dehydrogenase), while FADH2
donates its electrons to Complex II.
4. Which part of an amino acid defines its chemical properties and classification
(e.g., polar, non-polar, acidic, basic)?
A. The amino group
B. The carboxyl group
C. The R-group (side chain)
D. The alpha carbon
Answer: C
Rationale: While all amino acids share the amino and carboxyl groups, it is the unique
chemical structure of the R-group (side chain) that determines the specific properties of
each amino acid.
5. What is the primary role of myoglobin in human physiology?
A. Storing oxygen in muscle cells for immediate use
B. Transporting oxygen from lungs to tissues
C. Transporting carbon dioxide to the lungs
D. Buffering the pH of the blood
Answer: A
Rationale: Myoglobin has a high affinity for oxygen and acts as a storage reservoir in
muscle tissue, whereas hemoglobin is responsible for systemic transport.
, 6. Which of the following describes the ‘Bohr Effect’ regarding hemoglobin?
A. High pH increases oxygen affinity
B. Low 2,3-BPG levels favor the T-state
C. High CO2 and low pH decrease oxygen affinity, favoring oxygen release
D. Increased temperature increases oxygen binding
Answer: C
Rationale: The Bohr Effect describes how hydrogen ions (low pH) and carbon dioxide
stabilize the T-state (deoxygenated) of hemoglobin, facilitating the release of oxygen in
metabolically active tissues.
7. In DNA replication, which enzyme is responsible for unwinding the double
helix at the replication fork?
A. Helicase
B. Ligase
C. DNA Polymerase III
D. Topoisomerase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of DNA for replication.
8. Which process results in the production of two pyruvates, two ATP (net), and
two NADH from one glucose molecule?
A. Glycolysis
B. Citric Acid Cycle
C. Gluconeogenesis
D. Oxidative Phosphorylation
Answer: A
Rationale: Glycolysis occurs in the cytosol and is the initial breakdown of glucose into two
pyruvate molecules, yielding a net of 2 ATP and 2 NADH.
