BCHM 270 Biochemistry Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which statement best describes the central focus of biochemistry as a
discipline and explains why biochemical knowledge is essential for
understanding normal human physiology as well as disease processes?
A. It focuses exclusively on the identification of inorganic minerals in
biological tissues.
B. It studies the chemical composition of living organisms and the
molecular reactions and interactions that sustain life.
C. It is primarily concerned with the classification of organisms
according to evolutionary relationships.
D. It studies only the physical structure of organs without considering
molecular processes.
Answer: B.
Biochemistry examines the molecules of life and the chemical
reactions occurring within cells, thereby providing a molecular
, explanation for physiological processes, metabolism, signaling, and
many disease mechanisms.
2. Which property of water is most directly responsible for its ability to
dissolve many ionic and polar biological substances and thereby serve
as the principal solvent in cells?
A. Its low specific heat
B. Its nonpolar covalent structure
C. Its polarity and ability to form hydrogen bonds
D. Its inability to interact with charged molecules
Answer: C.
Water is a polar molecule with partial positive and negative charges
that interact strongly with ions and polar molecules, making it an
exceptionally important biological solvent.
3. A biochemical reaction releases hydrogen ions into an aqueous
solution. Which change would most directly indicate that the solution
has become more acidic?
A. An increase in pH
B. A decrease in hydrogen-ion concentration
C. An increase in hydrogen-ion concentration
D. An increase in hydroxide-ion concentration
Answer: C.
Acidity is directly related to hydrogen-ion concentration; increasing
, hydrogen-ion concentration lowers pH and makes a solution more
acidic.
4. A buffer is particularly important in biological systems because it can
resist changes in pH when relatively small amounts of acid or base are
added. Which combination is required for an effective buffer system?
A. A strong acid and a strong base at equal concentrations
B. A weak acid and its conjugate base
C. A nonpolar lipid and a carbohydrate
D. A protein and an insoluble mineral
Answer: B.
A buffer consists of a weak acid and its conjugate base, allowing it to
consume added hydrogen ions or hydroxide ions and thereby
minimize changes in pH.
5. The Henderson–Hasselbalch equation is commonly used to describe
buffer behavior. When the concentrations of a weak acid and its
conjugate base are equal, what is the relationship between pH and
pKa?
A. pH is approximately equal to pKa
B. pH is twice the pKa
C. pH is always zero
D. pH is unrelated to pKa
Answer: A.
When the acid and conjugate-base concentrations are equal, their
, concentration ratio is one and its logarithm is zero, so the
Henderson–Hasselbalch equation gives pH = pKa.
6. Which amino acid contains a thiol group that can participate in the
formation of disulfide bonds in proteins?
A. Serine
B. Cysteine
C. Methionine
D. Lysine
Answer: B.
Cysteine contains a reactive sulfhydryl or thiol group, and two
cysteine residues can be oxidized to form a stabilizing disulfide bond.
7. Which amino acid is classified as a basic amino acid because its side
chain can become positively charged at physiological pH?
A. Aspartate
B. Glutamate
C. Lysine
D. Valine
Answer: C.
Lysine has an amino-containing side chain with a relatively high pKa,
allowing it to remain positively charged under physiological
conditions.
8. Which structural feature distinguishes an α-amino acid from many
other organic molecules and allows amino acids to serve as the
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which statement best describes the central focus of biochemistry as a
discipline and explains why biochemical knowledge is essential for
understanding normal human physiology as well as disease processes?
A. It focuses exclusively on the identification of inorganic minerals in
biological tissues.
B. It studies the chemical composition of living organisms and the
molecular reactions and interactions that sustain life.
C. It is primarily concerned with the classification of organisms
according to evolutionary relationships.
D. It studies only the physical structure of organs without considering
molecular processes.
Answer: B.
Biochemistry examines the molecules of life and the chemical
reactions occurring within cells, thereby providing a molecular
, explanation for physiological processes, metabolism, signaling, and
many disease mechanisms.
2. Which property of water is most directly responsible for its ability to
dissolve many ionic and polar biological substances and thereby serve
as the principal solvent in cells?
A. Its low specific heat
B. Its nonpolar covalent structure
C. Its polarity and ability to form hydrogen bonds
D. Its inability to interact with charged molecules
Answer: C.
Water is a polar molecule with partial positive and negative charges
that interact strongly with ions and polar molecules, making it an
exceptionally important biological solvent.
3. A biochemical reaction releases hydrogen ions into an aqueous
solution. Which change would most directly indicate that the solution
has become more acidic?
A. An increase in pH
B. A decrease in hydrogen-ion concentration
C. An increase in hydrogen-ion concentration
D. An increase in hydroxide-ion concentration
Answer: C.
Acidity is directly related to hydrogen-ion concentration; increasing
, hydrogen-ion concentration lowers pH and makes a solution more
acidic.
4. A buffer is particularly important in biological systems because it can
resist changes in pH when relatively small amounts of acid or base are
added. Which combination is required for an effective buffer system?
A. A strong acid and a strong base at equal concentrations
B. A weak acid and its conjugate base
C. A nonpolar lipid and a carbohydrate
D. A protein and an insoluble mineral
Answer: B.
A buffer consists of a weak acid and its conjugate base, allowing it to
consume added hydrogen ions or hydroxide ions and thereby
minimize changes in pH.
5. The Henderson–Hasselbalch equation is commonly used to describe
buffer behavior. When the concentrations of a weak acid and its
conjugate base are equal, what is the relationship between pH and
pKa?
A. pH is approximately equal to pKa
B. pH is twice the pKa
C. pH is always zero
D. pH is unrelated to pKa
Answer: A.
When the acid and conjugate-base concentrations are equal, their
, concentration ratio is one and its logarithm is zero, so the
Henderson–Hasselbalch equation gives pH = pKa.
6. Which amino acid contains a thiol group that can participate in the
formation of disulfide bonds in proteins?
A. Serine
B. Cysteine
C. Methionine
D. Lysine
Answer: B.
Cysteine contains a reactive sulfhydryl or thiol group, and two
cysteine residues can be oxidized to form a stabilizing disulfide bond.
7. Which amino acid is classified as a basic amino acid because its side
chain can become positively charged at physiological pH?
A. Aspartate
B. Glutamate
C. Lysine
D. Valine
Answer: C.
Lysine has an amino-containing side chain with a relatively high pKa,
allowing it to remain positively charged under physiological
conditions.
8. Which structural feature distinguishes an α-amino acid from many
other organic molecules and allows amino acids to serve as the
