C785 Biochemistry Modules 1–2 Assessment 2026 |WGU
1. Which property of water allows it to act as an efficient solvent for polar
molecules?
A. High specific heat
B. Polarity and hydrogen bonding capacity
C. Low density as a solid
D. High surface tension
Answer: B
Rationale: Water’s polarity allows it to form electrostatic interactions with other polar
molecules and ions, making it an excellent solvent.
2. In a water molecule, the oxygen atom carries a partial negative charge
because:
A. It is more electronegative than hydrogen
B. It has a lower atomic mass than hydrogen
C. It shares electrons equally with hydrogen
D. It has more protons than electrons
Answer: A
Rationale: Oxygen is more electronegative, meaning it pulls the shared electrons closer to
itself than the hydrogen atoms do.
,3. What is the maximum number of hydrogen bonds a single water molecule
can form?
A. 2
B. 4
C. 3
D. 6
Answer: B
Rationale: A water molecule can form four hydrogen bonds: two through the lone pairs on
oxygen and two through the hydrogen atoms.
4. If the pH of a solution changes from 7 to 5, the concentration of H+ ions has:
A. Increased by a factor of 2
B. Decreased by a factor of 100
C. Increased by a factor of 100
D. Stayed the same
Answer: C
Rationale: The pH scale is logarithmic; a change of 2 units represents a 10^2 or 100-fold
change in H+ concentration.
5. Which of the following describes a buffer?
A. A system that resists changes in pH by accepting or donating H+ ions
B. A substance that increases the rate of a reaction
C. A molecule that only functions at pH 7.0
D. A catalyst for hydrolytic reactions
Answer: A
Rationale: Buffers consist of weak acids and their conjugate bases that minimize changes
in pH when OH- or H+ is added.
, 6. What type of bond is formed between two amino acids during protein
synthesis?
A. Ionic bond
B. Peptide bond
C. Hydrogen bond
D. Phosphodiester bond
Answer: B
Rationale: A peptide bond is a covalent bond formed between the carboxyl group of one
amino acid and the amino group of another.
7. Which part of an amino acid determines its unique chemical properties?
A. The amino group
B. The carboxyl group
C. The side chain (R group)
D. The alpha carbon
Answer: C
Rationale: The R group or side chain varies between the 20 standard amino acids and
determines their chemical nature.
8. Secondary structure of a protein is primarily stabilized by:
A. Disulfide bridges
B. Ionic bonds between side chains
C. Hydrophobic interactions between R groups
D. Hydrogen bonds between backbone atoms
Answer: D
Rationale: Alpha-helices and beta-sheets are stabilized by hydrogen bonding between the
carbonyl oxygen and amide hydrogen of the polypeptide backbone.
1. Which property of water allows it to act as an efficient solvent for polar
molecules?
A. High specific heat
B. Polarity and hydrogen bonding capacity
C. Low density as a solid
D. High surface tension
Answer: B
Rationale: Water’s polarity allows it to form electrostatic interactions with other polar
molecules and ions, making it an excellent solvent.
2. In a water molecule, the oxygen atom carries a partial negative charge
because:
A. It is more electronegative than hydrogen
B. It has a lower atomic mass than hydrogen
C. It shares electrons equally with hydrogen
D. It has more protons than electrons
Answer: A
Rationale: Oxygen is more electronegative, meaning it pulls the shared electrons closer to
itself than the hydrogen atoms do.
,3. What is the maximum number of hydrogen bonds a single water molecule
can form?
A. 2
B. 4
C. 3
D. 6
Answer: B
Rationale: A water molecule can form four hydrogen bonds: two through the lone pairs on
oxygen and two through the hydrogen atoms.
4. If the pH of a solution changes from 7 to 5, the concentration of H+ ions has:
A. Increased by a factor of 2
B. Decreased by a factor of 100
C. Increased by a factor of 100
D. Stayed the same
Answer: C
Rationale: The pH scale is logarithmic; a change of 2 units represents a 10^2 or 100-fold
change in H+ concentration.
5. Which of the following describes a buffer?
A. A system that resists changes in pH by accepting or donating H+ ions
B. A substance that increases the rate of a reaction
C. A molecule that only functions at pH 7.0
D. A catalyst for hydrolytic reactions
Answer: A
Rationale: Buffers consist of weak acids and their conjugate bases that minimize changes
in pH when OH- or H+ is added.
, 6. What type of bond is formed between two amino acids during protein
synthesis?
A. Ionic bond
B. Peptide bond
C. Hydrogen bond
D. Phosphodiester bond
Answer: B
Rationale: A peptide bond is a covalent bond formed between the carboxyl group of one
amino acid and the amino group of another.
7. Which part of an amino acid determines its unique chemical properties?
A. The amino group
B. The carboxyl group
C. The side chain (R group)
D. The alpha carbon
Answer: C
Rationale: The R group or side chain varies between the 20 standard amino acids and
determines their chemical nature.
8. Secondary structure of a protein is primarily stabilized by:
A. Disulfide bridges
B. Ionic bonds between side chains
C. Hydrophobic interactions between R groups
D. Hydrogen bonds between backbone atoms
Answer: D
Rationale: Alpha-helices and beta-sheets are stabilized by hydrogen bonding between the
carbonyl oxygen and amide hydrogen of the polypeptide backbone.
