WGU C785 Biochemistry Unit Exams 2024/2025 – Questions
and Answers with Complete Solutions | Latest Edition
Question 1:
Which level of protein structure is disrupted through the hydrolysis of peptide bonds?
A) Quaternary
B) Tertiary
C) Primary
D) Secondary
Correct Answer: C
Solution: The primary structure of a protein is the sequence of amino acids held together by
peptide bonds. Hydrolysis of these bonds breaks the linear chain, disrupting the primary
structure. Quaternary (A) involves subunit interactions, tertiary (B) 3D folding, and secondary
(D) local conformations like helices, all dependent on intact primary structure.
Question 2:
A mutation in the beta-hemoglobin gene, which results in the replacement of the amino acid
glutamate in position 6 with the amino acid valine, leads to the development of sickle cell
anemia. This is an example of which type of mutation?
A) Nonsense mutation
B) Missense mutation
C) Frameshift mutation
D) Silent mutation
Correct Answer: B
Solution: A missense mutation changes one amino acid to another (glutamate to valine at
position 6 in β-globin), altering protein function and causing sickling under low oxygen.
Nonsense (A) creates a premature stop codon. Frameshift (C) shifts the reading frame via
insertion/deletion. Silent (D) changes the codon but not the amino acid due to degeneracy.
Question 3:
Which type of bond primarily stabilizes the secondary structure of proteins (α-helices and
β-sheets)?
A) Ionic bonds
B) Hydrogen bonds
C) Disulfide bridges
D) Hydrophobic interactions
,Correct Answer: B
Solution: Hydrogen bonds between the carbonyl oxygen of one amino acid and the amide
hydrogen of another (four residues away in α-helices or between strands in β-sheets) stabilize
secondary structure. Ionic bonds (A) and disulfide bridges (C) stabilize tertiary/quaternary.
Hydrophobic interactions (D) drive tertiary folding but not secondary.
Question 4:
Both of these amino acids are non-polar and therefore can interact together with a hydrophobic
interaction. Please note that the "S" in the amino acid on the right is non-polar, while the "SH"
group in answer choice D is polar. (Assuming vignette with images of isoleucine and valine vs.
cysteine.)
A) Isoleucine and valine
B) Leucine and phenylalanine
C) Cysteine and methionine
D) Glycine and serine
Correct Answer: A
Solution: Isoleucine and valine are both non-polar aliphatic amino acids, forming hydrophobic
interactions in protein cores. Leucine/phenylalanine (B) also non-polar but vignette-specific.
Cysteine (C) has polar SH. Glycine (D) non-polar but serine polar.
Question 5:
What is the basic structure of an amino acid? What do they look like?
A) Central carbon with amino group, carboxyl group, hydrogen, and R side chain
B) Linear chain of carbons
C) Ring structure with nitrogens
D) Phosphate backbone
Correct Answer: A
Solution: Amino acids have a central α-carbon attached to an amino group (-NH2), carboxyl
group (-COOH), hydrogen, and variable R side chain determining properties. Linear (B) fatty
acids. Ring (C) nucleotides. Phosphate (D) DNA/RNA.
Question 6:
How do you identify the 3 different types of side chains: non-polar, polar uncharged, and
charged?
A) Non-polar (hydrophobic), polar uncharged (H-bond), charged (acidic/basic)
B) All hydrophobic
C) All polar
D) No classification
,Correct Answer: A
Solution: Side chains classify by polarity/charge: non-polar (e.g., valine, hydrophobic core),
polar uncharged (e.g., serine, H-bonding), charged (acidic like aspartate negative, basic like
lysine positive). All same (B, C) false. Classification key (D) false.
Question 7:
The capacity to cause change, especially to do work (to move matter against an opposing
force).
A) Energy
B) Entropy
C) Force
D) Power
Correct Answer: A
Solution: Energy is the capacity for work, including kinetic/ potential in biochemical reactions
(e.g., ATP hydrolysis). Entropy (B) disorder. Force (C) push/pull. Power (D) work/time.
Question 8:
A type of strong chemical bond in which two atoms share one or more pairs of valence
electrons.
A) Covalent bond
B) Ionic bond
C) Hydrogen bond
D) Van der Waals
Correct Answer: A
Solution: Covalent bonds share electrons (single/double/triple) for stable molecules like
proteins. Ionic (B) transfer. Hydrogen (C) weak. Van der Waals (D) weakest.
Question 9:
A chemical bond resulting from the attraction between oppositely charged ions.
A) Ionic bond
B) Covalent bond
C) Metallic bond
D) Coordinate bond
Correct Answer: A
, Solution: Ionic bonds form between metals/non-metals via electron transfer (e.g., NaCl in salts).
Covalent (B) sharing. Metallic (C) delocalized electrons. Coordinate (D) shared pair from one
atom.
Question 10:
What is the pH scale range?
A) 0 to 14
B) -1 to 15
C) 1 to 13
D) 0 to 7 only
Correct Answer: A
Solution: pH = -log[H+], 0-14 covers acidic (0-7) to basic (7-14), neutral 7 at 25°C. Extended (B)
rare. Limited (C, D) incomplete.
Question 11:
Which property of enzymes is illustrated in the final step of the enzymatic cycle?
A) Enzymes are reusable
B) Specificity
C) Catalysis
D) Inhibition
Correct Answer: A
Solution: Enzymes return to native form after product release, reusable for multiple cycles.
Specificity (B) substrate fit. Catalysis (C) lowers Ea. Inhibition (D) blocks.
Question 12:
In the enzyme cycle, which step immediately follows induced fit?
A) Formation of the enzyme-product complex
B) Substrate binding
C) Catalysis
D) Product release
Correct Answer: A
Solution: Induced fit forms ES complex, then catalysis; product forms EP complex (A). Binding
(B) before fit. Catalysis (C) in ES. Release (D) after.
Question 13:
The optimum pH for enzymes varies for different enzymes and even enzymes with similar
actions may have different optimal pH based on where they act. For example, trypsin, a
and Answers with Complete Solutions | Latest Edition
Question 1:
Which level of protein structure is disrupted through the hydrolysis of peptide bonds?
A) Quaternary
B) Tertiary
C) Primary
D) Secondary
Correct Answer: C
Solution: The primary structure of a protein is the sequence of amino acids held together by
peptide bonds. Hydrolysis of these bonds breaks the linear chain, disrupting the primary
structure. Quaternary (A) involves subunit interactions, tertiary (B) 3D folding, and secondary
(D) local conformations like helices, all dependent on intact primary structure.
Question 2:
A mutation in the beta-hemoglobin gene, which results in the replacement of the amino acid
glutamate in position 6 with the amino acid valine, leads to the development of sickle cell
anemia. This is an example of which type of mutation?
A) Nonsense mutation
B) Missense mutation
C) Frameshift mutation
D) Silent mutation
Correct Answer: B
Solution: A missense mutation changes one amino acid to another (glutamate to valine at
position 6 in β-globin), altering protein function and causing sickling under low oxygen.
Nonsense (A) creates a premature stop codon. Frameshift (C) shifts the reading frame via
insertion/deletion. Silent (D) changes the codon but not the amino acid due to degeneracy.
Question 3:
Which type of bond primarily stabilizes the secondary structure of proteins (α-helices and
β-sheets)?
A) Ionic bonds
B) Hydrogen bonds
C) Disulfide bridges
D) Hydrophobic interactions
,Correct Answer: B
Solution: Hydrogen bonds between the carbonyl oxygen of one amino acid and the amide
hydrogen of another (four residues away in α-helices or between strands in β-sheets) stabilize
secondary structure. Ionic bonds (A) and disulfide bridges (C) stabilize tertiary/quaternary.
Hydrophobic interactions (D) drive tertiary folding but not secondary.
Question 4:
Both of these amino acids are non-polar and therefore can interact together with a hydrophobic
interaction. Please note that the "S" in the amino acid on the right is non-polar, while the "SH"
group in answer choice D is polar. (Assuming vignette with images of isoleucine and valine vs.
cysteine.)
A) Isoleucine and valine
B) Leucine and phenylalanine
C) Cysteine and methionine
D) Glycine and serine
Correct Answer: A
Solution: Isoleucine and valine are both non-polar aliphatic amino acids, forming hydrophobic
interactions in protein cores. Leucine/phenylalanine (B) also non-polar but vignette-specific.
Cysteine (C) has polar SH. Glycine (D) non-polar but serine polar.
Question 5:
What is the basic structure of an amino acid? What do they look like?
A) Central carbon with amino group, carboxyl group, hydrogen, and R side chain
B) Linear chain of carbons
C) Ring structure with nitrogens
D) Phosphate backbone
Correct Answer: A
Solution: Amino acids have a central α-carbon attached to an amino group (-NH2), carboxyl
group (-COOH), hydrogen, and variable R side chain determining properties. Linear (B) fatty
acids. Ring (C) nucleotides. Phosphate (D) DNA/RNA.
Question 6:
How do you identify the 3 different types of side chains: non-polar, polar uncharged, and
charged?
A) Non-polar (hydrophobic), polar uncharged (H-bond), charged (acidic/basic)
B) All hydrophobic
C) All polar
D) No classification
,Correct Answer: A
Solution: Side chains classify by polarity/charge: non-polar (e.g., valine, hydrophobic core),
polar uncharged (e.g., serine, H-bonding), charged (acidic like aspartate negative, basic like
lysine positive). All same (B, C) false. Classification key (D) false.
Question 7:
The capacity to cause change, especially to do work (to move matter against an opposing
force).
A) Energy
B) Entropy
C) Force
D) Power
Correct Answer: A
Solution: Energy is the capacity for work, including kinetic/ potential in biochemical reactions
(e.g., ATP hydrolysis). Entropy (B) disorder. Force (C) push/pull. Power (D) work/time.
Question 8:
A type of strong chemical bond in which two atoms share one or more pairs of valence
electrons.
A) Covalent bond
B) Ionic bond
C) Hydrogen bond
D) Van der Waals
Correct Answer: A
Solution: Covalent bonds share electrons (single/double/triple) for stable molecules like
proteins. Ionic (B) transfer. Hydrogen (C) weak. Van der Waals (D) weakest.
Question 9:
A chemical bond resulting from the attraction between oppositely charged ions.
A) Ionic bond
B) Covalent bond
C) Metallic bond
D) Coordinate bond
Correct Answer: A
, Solution: Ionic bonds form between metals/non-metals via electron transfer (e.g., NaCl in salts).
Covalent (B) sharing. Metallic (C) delocalized electrons. Coordinate (D) shared pair from one
atom.
Question 10:
What is the pH scale range?
A) 0 to 14
B) -1 to 15
C) 1 to 13
D) 0 to 7 only
Correct Answer: A
Solution: pH = -log[H+], 0-14 covers acidic (0-7) to basic (7-14), neutral 7 at 25°C. Extended (B)
rare. Limited (C, D) incomplete.
Question 11:
Which property of enzymes is illustrated in the final step of the enzymatic cycle?
A) Enzymes are reusable
B) Specificity
C) Catalysis
D) Inhibition
Correct Answer: A
Solution: Enzymes return to native form after product release, reusable for multiple cycles.
Specificity (B) substrate fit. Catalysis (C) lowers Ea. Inhibition (D) blocks.
Question 12:
In the enzyme cycle, which step immediately follows induced fit?
A) Formation of the enzyme-product complex
B) Substrate binding
C) Catalysis
D) Product release
Correct Answer: A
Solution: Induced fit forms ES complex, then catalysis; product forms EP complex (A). Binding
(B) before fit. Catalysis (C) in ES. Release (D) after.
Question 13:
The optimum pH for enzymes varies for different enzymes and even enzymes with similar
actions may have different optimal pH based on where they act. For example, trypsin, a
