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Test Bank – Biochemistry: A Short Course, 4th
Edition | Complete Exam Questions & Answers
for All Chapters | Comprehensive Review for
Pre-Med, Nursing, and Health Science
Programs
SECTION 1: THE MOLECULAR DESIGN OF LIFE – BIOCHEMICAL
FOUNDATIONS (Questions 1–15)
1. A biochemist is studying a newly discovered biomolecule that
contains carbon, hydrogen, oxygen, nitrogen, and sulfur. This molecule
is most likely which class of biomolecule?
A. Carbohydrate
B. Lipid
C. Protein
D. Nucleic acid
Exact answer:C
Explanation: Proteins are the only major class of biomolecules that
consistently contain sulfur (in the amino acids cysteine and
methionine), in addition to carbon, hydrogen, oxygen, and nitrogen.
Carbohydrates and lipids typically lack nitrogen and sulfur, while nucleic
acids contain phosphorus but not sulfur.
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2. Which statement best describes the central dogma of molecular
biology?
A. RNA is transcribed into DNA, which is translated into protein
B. DNA is replicated, then transcribed into RNA, which is translated into
protein
C. Proteins are transcribed into RNA, which is translated into DNA
D. DNA is directly translated into protein without an RNA intermediate
Exact answer:B
Explanation: The central dogma describes the flow of genetic
information: DNA → RNA → Protein. DNA is first transcribed into RNA,
and RNA is then translated into protein. This fundamental principle
underlies all of molecular biology.
3. A solution contains a weak acid with a pKa of 4.76. At a pH of 6.76,
what is the ratio of the concentration of the conjugate base to the
acid?
A. 1:1
B. 10:1
C. 100:1
D. 1:10
Exact answer:C
Explanation: Using the Henderson-Hasselbalch equation: pH = pKa +
log([A⁻]/[HA]). 6.76 = 4.76 + log([A⁻]/[HA]), so log([A⁻]/[HA]) = 2.0, and
[A⁻]/[HA] = 100. Thus, the conjugate base is present at 100 times the
concentration of the acid.
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4. A researcher is investigating the interactions that stabilize protein
structure. Which type of interaction is primarily responsible for the
hydrophobic effect that drives protein folding?
A. Hydrogen bonds between polar side chains
B. Ionic interactions between charged residues
C. Clustering of nonpolar side chains away from water
D. Disulfide bonds between cysteine residues
Exact answer:C
Explanation: The hydrophobic effect is the tendency of nonpolar
molecules to cluster together in aqueous solution to minimize their
contact with water. This is the primary driving force for protein folding,
as hydrophobic side chains are buried in the protein interior.
5. Which functional group is characteristic of a carboxylic acid?
A. –OH
B. –NH₂
C. –COOH
D. –CHO
Exact answer:C
Explanation: The carboxyl group (–COOH) is the defining functional
group of carboxylic acids. It consists of a carbonyl group (C=O) attached
to a hydroxyl group (–OH). This group can donate a proton, making
carboxylic acids weak acids.
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6. A biochemist is studying a protein that contains 250 amino acids.
What is the approximate molecular weight of this protein?
A. 2,750 Da
B. 13,750 Da
C. 27,500 Da
D. 55,000 Da
Exact answer:C
Explanation: The average molecular weight of an amino acid residue is
approximately 110 Da. Therefore, a protein with 250 amino acids has an
approximate molecular weight of 250 × 110 = 27,500 Da (27.5 kDa).
7. A scientist is studying a membrane protein. Which statement about
membranes is correct?
A. Membranes are composed primarily of nucleic acids
B. Membranes define the cell and carry out cellular functions
C. Membranes are not involved in protein sorting
D. Membranes are impermeable to all molecules
Exact answer:B
Explanation: Membranes define the boundaries of the cell and its
organelles and carry out essential cellular functions including transport,
signaling, and compartmentalization. They are composed primarily of
lipids and proteins.
Test Bank – Biochemistry: A Short Course, 4th
Edition | Complete Exam Questions & Answers
for All Chapters | Comprehensive Review for
Pre-Med, Nursing, and Health Science
Programs
SECTION 1: THE MOLECULAR DESIGN OF LIFE – BIOCHEMICAL
FOUNDATIONS (Questions 1–15)
1. A biochemist is studying a newly discovered biomolecule that
contains carbon, hydrogen, oxygen, nitrogen, and sulfur. This molecule
is most likely which class of biomolecule?
A. Carbohydrate
B. Lipid
C. Protein
D. Nucleic acid
Exact answer:C
Explanation: Proteins are the only major class of biomolecules that
consistently contain sulfur (in the amino acids cysteine and
methionine), in addition to carbon, hydrogen, oxygen, and nitrogen.
Carbohydrates and lipids typically lack nitrogen and sulfur, while nucleic
acids contain phosphorus but not sulfur.
, 2
2. Which statement best describes the central dogma of molecular
biology?
A. RNA is transcribed into DNA, which is translated into protein
B. DNA is replicated, then transcribed into RNA, which is translated into
protein
C. Proteins are transcribed into RNA, which is translated into DNA
D. DNA is directly translated into protein without an RNA intermediate
Exact answer:B
Explanation: The central dogma describes the flow of genetic
information: DNA → RNA → Protein. DNA is first transcribed into RNA,
and RNA is then translated into protein. This fundamental principle
underlies all of molecular biology.
3. A solution contains a weak acid with a pKa of 4.76. At a pH of 6.76,
what is the ratio of the concentration of the conjugate base to the
acid?
A. 1:1
B. 10:1
C. 100:1
D. 1:10
Exact answer:C
Explanation: Using the Henderson-Hasselbalch equation: pH = pKa +
log([A⁻]/[HA]). 6.76 = 4.76 + log([A⁻]/[HA]), so log([A⁻]/[HA]) = 2.0, and
[A⁻]/[HA] = 100. Thus, the conjugate base is present at 100 times the
concentration of the acid.
, 3
4. A researcher is investigating the interactions that stabilize protein
structure. Which type of interaction is primarily responsible for the
hydrophobic effect that drives protein folding?
A. Hydrogen bonds between polar side chains
B. Ionic interactions between charged residues
C. Clustering of nonpolar side chains away from water
D. Disulfide bonds between cysteine residues
Exact answer:C
Explanation: The hydrophobic effect is the tendency of nonpolar
molecules to cluster together in aqueous solution to minimize their
contact with water. This is the primary driving force for protein folding,
as hydrophobic side chains are buried in the protein interior.
5. Which functional group is characteristic of a carboxylic acid?
A. –OH
B. –NH₂
C. –COOH
D. –CHO
Exact answer:C
Explanation: The carboxyl group (–COOH) is the defining functional
group of carboxylic acids. It consists of a carbonyl group (C=O) attached
to a hydroxyl group (–OH). This group can donate a proton, making
carboxylic acids weak acids.
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6. A biochemist is studying a protein that contains 250 amino acids.
What is the approximate molecular weight of this protein?
A. 2,750 Da
B. 13,750 Da
C. 27,500 Da
D. 55,000 Da
Exact answer:C
Explanation: The average molecular weight of an amino acid residue is
approximately 110 Da. Therefore, a protein with 250 amino acids has an
approximate molecular weight of 250 × 110 = 27,500 Da (27.5 kDa).
7. A scientist is studying a membrane protein. Which statement about
membranes is correct?
A. Membranes are composed primarily of nucleic acids
B. Membranes define the cell and carry out cellular functions
C. Membranes are not involved in protein sorting
D. Membranes are impermeable to all molecules
Exact answer:B
Explanation: Membranes define the boundaries of the cell and its
organelles and carry out essential cellular functions including transport,
signaling, and compartmentalization. They are composed primarily of
lipids and proteins.
