CHEM 210 BIOCHEMISTRY MODULE 1 EXAM 2026/2027 |
Foundations: Water, pH & Biomolecules | Latest Q&A Verified
| Portage Learning | Pass Guaranteed - A+ Graded
Q1: Which of the following best defines biochemistry as a scientific discipline?
A. The study of living organisms at the organismal level only
B. The study of chemical processes within and relating to living organisms [CORRECT]
C. The study of inorganic compounds in geological formations
D. The study of quantum mechanics in atomic structures
Correct Answer: B
Rationale: Biochemistry is fundamentally the study of chemical processes within and
relating to living organisms. It bridges biology and chemistry by examining the
molecular mechanisms that underlie life processes, including metabolism, enzyme
catalysis, DNA replication, and protein synthesis. Option A is incorrect because
biochemistry operates at the molecular and cellular levels, not primarily at the
organismal level (which is more ecology/physiology). Option C is incorrect because
inorganic geology falls under geochemistry or mineralogy, not biochemistry. Option D is
incorrect because quantum mechanics of atomic structures is the domain of physical
chemistry and quantum chemistry, though quantum effects are relevant in some
biochemical processes (photosynthesis, enzyme catalysis).
Q2: In a water molecule, the oxygen atom has a partial negative charge (δ-) and the
hydrogen atoms have partial positive charges (δ+) because:
A. Oxygen has lower electronegativity than hydrogen
B. The oxygen-hydrogen bonds are nonpolar covalent
,C. Oxygen has higher electronegativity than hydrogen, creating an unequal sharing of
electrons [CORRECT]
D. The molecule has a linear geometry with symmetrical charge distribution
Correct Answer: C
Rationale: Electronegativity is the ability of an atom to attract electrons in a chemical
bond. Oxygen has an electronegativity of 3.44 (Pauling scale) versus hydrogen's 2.20.
This significant difference causes oxygen to pull electron density toward itself, creating
partial negative charge, while hydrogen atoms bear partial positive charge. This polarity
makes water an excellent solvent. Option A is incorrect because oxygen has higher, not
lower, electronegativity than hydrogen. Option B is incorrect because O-H bonds are
polar covalent, not nonpolar (electronegativity difference ~1.24). Option D is incorrect
because water has bent (angular) geometry (~104.5° bond angle), not linear; the bent
shape creates a net dipole moment.
Q3: Calculate the pH of a solution with [H⁺] = 2.5 × 10⁻⁴ M.
A. 3.40
B. 3.60 [CORRECT]
C. 4.40
D. 10.40
Correct Answer: B
Rationale: pH is calculated using the formula: pH = -log[H⁺]
Step 1: pH = -log(2.5 × 10⁻⁴)
Step 2: Using logarithm properties: log(2.5 × 10⁻⁴) = log(2.5) + log(10⁻⁴) = 0.398 - 4 =
-3.602
Step 3: pH = -(-3.602) = 3.60
Option A is incorrect because 3.40 would result from [H⁺] = 4.0 × 10⁻⁴ M. Option C is
incorrect because 4.40 would result from [H⁺] = 4.0 × 10⁻⁵ M (error in exponent). Option
, D is incorrect because 10.40 would be the pOH, not pH (or results from using [OH⁻]
instead of [H⁺]).
Q4: Which type of chemical bond is primarily responsible for the tertiary structure of
proteins?
A. Peptide bonds between adjacent amino acids
B. Hydrogen bonds between carbonyl and amide groups in the backbone
C. Hydrophobic interactions, disulfide bonds, hydrogen bonds, and ionic interactions
between R groups [CORRECT]
D. Phosphodiester bonds between nucleotides
Correct Answer: C
Rationale: Tertiary protein structure refers to the three-dimensional folding of a single
polypeptide chain, stabilized by interactions between amino acid side chains (R groups):
hydrophobic interactions (burying nonpolar residues), disulfide bridges (covalent S-S
bonds between cysteines), hydrogen bonds (between polar side chains), and ionic
bonds (salt bridges between charged residues). Option A is incorrect because peptide
bonds form the primary structure (linear sequence), not tertiary folding. Option B is
incorrect because backbone hydrogen bonds stabilize secondary structure (α-helices
and β-sheets), not tertiary structure. Option D is incorrect because phosphodiester
bonds are found in nucleic acids (DNA/RNA backbone), not proteins.
Q5: The Henderson-Hasselbalch equation is pH = pKa + log([A⁻]/[HA]). For a buffer
containing acetic acid (pKa = 4.76) and sodium acetate, what is the pH when [A⁻]/[HA] =
10?
A. 3.76
B. 4.76
C. 5.76 [CORRECT]
Foundations: Water, pH & Biomolecules | Latest Q&A Verified
| Portage Learning | Pass Guaranteed - A+ Graded
Q1: Which of the following best defines biochemistry as a scientific discipline?
A. The study of living organisms at the organismal level only
B. The study of chemical processes within and relating to living organisms [CORRECT]
C. The study of inorganic compounds in geological formations
D. The study of quantum mechanics in atomic structures
Correct Answer: B
Rationale: Biochemistry is fundamentally the study of chemical processes within and
relating to living organisms. It bridges biology and chemistry by examining the
molecular mechanisms that underlie life processes, including metabolism, enzyme
catalysis, DNA replication, and protein synthesis. Option A is incorrect because
biochemistry operates at the molecular and cellular levels, not primarily at the
organismal level (which is more ecology/physiology). Option C is incorrect because
inorganic geology falls under geochemistry or mineralogy, not biochemistry. Option D is
incorrect because quantum mechanics of atomic structures is the domain of physical
chemistry and quantum chemistry, though quantum effects are relevant in some
biochemical processes (photosynthesis, enzyme catalysis).
Q2: In a water molecule, the oxygen atom has a partial negative charge (δ-) and the
hydrogen atoms have partial positive charges (δ+) because:
A. Oxygen has lower electronegativity than hydrogen
B. The oxygen-hydrogen bonds are nonpolar covalent
,C. Oxygen has higher electronegativity than hydrogen, creating an unequal sharing of
electrons [CORRECT]
D. The molecule has a linear geometry with symmetrical charge distribution
Correct Answer: C
Rationale: Electronegativity is the ability of an atom to attract electrons in a chemical
bond. Oxygen has an electronegativity of 3.44 (Pauling scale) versus hydrogen's 2.20.
This significant difference causes oxygen to pull electron density toward itself, creating
partial negative charge, while hydrogen atoms bear partial positive charge. This polarity
makes water an excellent solvent. Option A is incorrect because oxygen has higher, not
lower, electronegativity than hydrogen. Option B is incorrect because O-H bonds are
polar covalent, not nonpolar (electronegativity difference ~1.24). Option D is incorrect
because water has bent (angular) geometry (~104.5° bond angle), not linear; the bent
shape creates a net dipole moment.
Q3: Calculate the pH of a solution with [H⁺] = 2.5 × 10⁻⁴ M.
A. 3.40
B. 3.60 [CORRECT]
C. 4.40
D. 10.40
Correct Answer: B
Rationale: pH is calculated using the formula: pH = -log[H⁺]
Step 1: pH = -log(2.5 × 10⁻⁴)
Step 2: Using logarithm properties: log(2.5 × 10⁻⁴) = log(2.5) + log(10⁻⁴) = 0.398 - 4 =
-3.602
Step 3: pH = -(-3.602) = 3.60
Option A is incorrect because 3.40 would result from [H⁺] = 4.0 × 10⁻⁴ M. Option C is
incorrect because 4.40 would result from [H⁺] = 4.0 × 10⁻⁵ M (error in exponent). Option
, D is incorrect because 10.40 would be the pOH, not pH (or results from using [OH⁻]
instead of [H⁺]).
Q4: Which type of chemical bond is primarily responsible for the tertiary structure of
proteins?
A. Peptide bonds between adjacent amino acids
B. Hydrogen bonds between carbonyl and amide groups in the backbone
C. Hydrophobic interactions, disulfide bonds, hydrogen bonds, and ionic interactions
between R groups [CORRECT]
D. Phosphodiester bonds between nucleotides
Correct Answer: C
Rationale: Tertiary protein structure refers to the three-dimensional folding of a single
polypeptide chain, stabilized by interactions between amino acid side chains (R groups):
hydrophobic interactions (burying nonpolar residues), disulfide bridges (covalent S-S
bonds between cysteines), hydrogen bonds (between polar side chains), and ionic
bonds (salt bridges between charged residues). Option A is incorrect because peptide
bonds form the primary structure (linear sequence), not tertiary folding. Option B is
incorrect because backbone hydrogen bonds stabilize secondary structure (α-helices
and β-sheets), not tertiary structure. Option D is incorrect because phosphodiester
bonds are found in nucleic acids (DNA/RNA backbone), not proteins.
Q5: The Henderson-Hasselbalch equation is pH = pKa + log([A⁻]/[HA]). For a buffer
containing acetic acid (pKa = 4.76) and sodium acetate, what is the pH when [A⁻]/[HA] =
10?
A. 3.76
B. 4.76
C. 5.76 [CORRECT]
