WGU C785 Biochemistry Exam 1 Practice 90 Questions | Accurate &
Verified Answers to Pass Actual Exam
1. Which of the following bonds connects the phosphate group of one
nucleotide to the sugar of the next in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Explanation: Phosphodiester bonds form the sugar-phosphate backbone of DNA and RNA
by linking the 3’ carbon of one sugar to the 5’ carbon of another.
2. In DNA replication, which enzyme is responsible for unwinding the double
helix?
A. Helicase
B. Ligase
C. DNA Polymerase
D. Primase
Answer: A
,Explanation: Helicase breaks the hydrogen bonds between the base pairs to separate the
DNA strands.
3. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Uracil
C. Adenine
D. Guanine
Answer: B
Explanation: RNA uses Uracil instead of Thymine, which is found in DNA.
4. The primary structure of a protein is held together by which type of bond?
A. Peptide bonds
B. Hydrogen bonds
C. Disulfide bridges
D. Hydrophobic interactions
Answer: A
Explanation: Primary structure refers to the sequence of amino acids joined by covalent
peptide bonds.
,5. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Explanation: Secondary structure is formed by hydrogen bonding between the backbone
atoms, creating regular patterns like helices and sheets.
6. What happens to the affinity of hemoglobin for oxygen when the pH
decreases (Bohr Effect)?
A. Affinity increases
B. Affinity remains unchanged
C. Affinity decreases
D. Hemoglobin denatures
Answer: C
Explanation: A decrease in pH (more acidic) stabilizes the T-state (deoxygenated) of
hemoglobin, decreasing its affinity for oxygen and promoting its release.
, 7. Which molecule acts as a competitive inhibitor in enzyme kinetics?
A. A molecule that binds to an allosteric site
B. A molecule that binds to the enzyme-substrate complex
C. A molecule that binds to the active site
D. A molecule that increases Vmax
Answer: C
Explanation: Competitive inhibitors compete with the substrate for the active site.
8. In the presence of a non-competitive inhibitor, what happens to the Vmax
and Km of an enzymatic reaction?
A. Both Vmax and Km decrease
B. Vmax stays the same, Km increases
C. Vmax increases, Km decreases
D. Vmax decreases, Km stays the same
Answer: D
Explanation: Non-competitive inhibitors reduce the overall reaction rate (lower Vmax)
but do not affect the binding affinity of the substrate (Km stays the same).
9. Which of the following is a characteristic of myoglobin?
A. It has a sigmoidal oxygen binding curve
B. It has a higher affinity for oxygen than hemoglobin
Verified Answers to Pass Actual Exam
1. Which of the following bonds connects the phosphate group of one
nucleotide to the sugar of the next in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Explanation: Phosphodiester bonds form the sugar-phosphate backbone of DNA and RNA
by linking the 3’ carbon of one sugar to the 5’ carbon of another.
2. In DNA replication, which enzyme is responsible for unwinding the double
helix?
A. Helicase
B. Ligase
C. DNA Polymerase
D. Primase
Answer: A
,Explanation: Helicase breaks the hydrogen bonds between the base pairs to separate the
DNA strands.
3. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Uracil
C. Adenine
D. Guanine
Answer: B
Explanation: RNA uses Uracil instead of Thymine, which is found in DNA.
4. The primary structure of a protein is held together by which type of bond?
A. Peptide bonds
B. Hydrogen bonds
C. Disulfide bridges
D. Hydrophobic interactions
Answer: A
Explanation: Primary structure refers to the sequence of amino acids joined by covalent
peptide bonds.
,5. Which level of protein structure is characterized by alpha-helices and beta-
pleated sheets?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Explanation: Secondary structure is formed by hydrogen bonding between the backbone
atoms, creating regular patterns like helices and sheets.
6. What happens to the affinity of hemoglobin for oxygen when the pH
decreases (Bohr Effect)?
A. Affinity increases
B. Affinity remains unchanged
C. Affinity decreases
D. Hemoglobin denatures
Answer: C
Explanation: A decrease in pH (more acidic) stabilizes the T-state (deoxygenated) of
hemoglobin, decreasing its affinity for oxygen and promoting its release.
, 7. Which molecule acts as a competitive inhibitor in enzyme kinetics?
A. A molecule that binds to an allosteric site
B. A molecule that binds to the enzyme-substrate complex
C. A molecule that binds to the active site
D. A molecule that increases Vmax
Answer: C
Explanation: Competitive inhibitors compete with the substrate for the active site.
8. In the presence of a non-competitive inhibitor, what happens to the Vmax
and Km of an enzymatic reaction?
A. Both Vmax and Km decrease
B. Vmax stays the same, Km increases
C. Vmax increases, Km decreases
D. Vmax decreases, Km stays the same
Answer: D
Explanation: Non-competitive inhibitors reduce the overall reaction rate (lower Vmax)
but do not affect the binding affinity of the substrate (Km stays the same).
9. Which of the following is a characteristic of myoglobin?
A. It has a sigmoidal oxygen binding curve
B. It has a higher affinity for oxygen than hemoglobin
