CHEM 210 BIOCHEMISTRY Portage Learning
Module 1-8 Exams & Final Exam
Comprehensive Review Questions with
Answers & Rationales
Question 1
Which of the following best defines organic chemistry?
A) The study of all carbon-containing compounds
B) The study of compounds containing carbon-hydrogen bonds
C) The study of compounds found only in living organisms
D) The study of compounds that contain oxygen
Correct Answer: B) The study of compounds containing carbon-
hydrogen bonds
Rationale: Organic chemistry is defined as the study of carbon-containing
compounds, specifically those with carbon-hydrogen (C-H) bonds. Inorganic
compounds may contain carbon (e.g., carbon dioxide, carbonates) but lack C-H
bonds.
A) Not all carbon-containing compounds are organic (e.g., CO₂, carbonates).
C) Organic compounds can be synthesized in the laboratory and are not
limited to living organisms.
D) Many organic compounds lack oxygen (e.g., hydrocarbons).
Question 2
Which scientist is credited with first synthesizing an organic compound from
inorganic starting materials, disproving vitalism?
A) Louis Pasteur
B) Friedrich Wöhler
C) August Kekulé
D) Linus Pauling
,Correct Answer: B) Friedrich Wöhler
Rationale: In 1828, Friedrich Wöhler synthesized urea (an organic
compound) from ammonium cyanate (an inorganic compound),
demonstrating that organic compounds could be created in the laboratory
without a "vital force."
A) Pasteur worked on fermentation and stereochemistry.
C) Kekulé proposed the structure of benzene.
D) Pauling worked on chemical bonding and protein structure.
Question 3
What are the four most abundant elements found in living organisms?
A) Carbon, Hydrogen, Oxygen, Nitrogen
B) Carbon, Hydrogen, Oxygen, Sodium
C) Carbon, Nitrogen, Oxygen, Phosphorus
D) Carbon, Hydrogen, Nitrogen, Sulfur
Correct Answer: A) Carbon, Hydrogen, Oxygen, Nitrogen
Rationale: These four elements make up approximately 96% of the mass of
most living organisms. They are considered "bulk elements" and form the
backbone of all major biomolecules: carbohydrates (C, H, O), proteins (C, H, O,
N, S), lipids (C, H, O), and nucleic acids (C, H, O, N, P).
B) Sodium is a trace element, not among the four most abundant.
C) Phosphorus is important but not among the top four by abundance.
D) Sulfur is present in some amino acids but is not among the top four.
Question 4
Which statement correctly describes water's role in biological systems?
A) Water is a poor solvent for charged molecules
B) Water can make up to 85% of a living organism's mass
C) Water is considered a non-polar solvent
D) Water molecules cannot form hydrogen bonds
,Correct Answer: B) Water can make up to 85% of a living organism's
mass
Rationale: Water is known as the "medium of life." In many organisms, water
constitutes 70-85% of total mass. Its polar nature allows it to serve as an
excellent solvent for ions and polar molecules. Water's ability to form
hydrogen bonds is critical for its unique properties.
A) Water is an excellent solvent for charged (polar) molecules and ions.
C) Water is a polar solvent due to its uneven charge distribution.
D) Water molecules readily form hydrogen bonds with other water molecules
and polar solutes.
Question 5
Which of the following is NOT a function of carbohydrates in cells?
A) Energy source for cells
B) Structural role in RNA
C) Structural role in DNA
D) Basis for building proteins
Correct Answer: D) Basis for building proteins
Rationale: Proteins are built from amino acids, not carbohydrates.
Carbohydrates serve as energy sources (glucose), structural components
(cellulose in plants, ribose in RNA/DNA), and metabolic intermediates. They
do not serve as the building blocks for protein synthesis.
A) Glucose is the primary energy source for most cells.
B) Ribose is a carbohydrate component of RNA.
C) Deoxyribose is a carbohydrate component of DNA.
Question 6
What is the pH of a solution with a hydrogen ion concentration of 1 × 10−7 M?
A) 5.0
B) 7.0
, C) 9.0
D) 1.0
Correct Answer: B) 7.0
Rationale: pH = -log[H⁺]. When [H⁺] = 1 × 10−7 M, pH = -log(10⁻⁷) = 7.0. Pure
water at 25°C has a pH of 7.0, which is neutral. Solutions with pH < 7 are
acidic; pH > 7 are basic.
A) pH 5.0 corresponds to [H⁺] = 1 × 10−5 M.
C) pH 9.0 corresponds to [H⁺] = 1 × 10−9 M.
D) pH 1.0 corresponds to [H⁺] = 1 × 10−1 M.
Question 7
A solution has a pH = 5.0. What is the concentration of OH⁻ in M?
A) 5 M
B) 10−5 M
C) 10−9 M
D) 10−1 M
Correct Answer: C) 10−9 M
Rationale: At 25°C, pH + pOH = 14. If pH = 5.0, then pOH = 9.0. [OH⁻] = 10⁻⁹
M. Alternatively, [H⁺] = 10⁻⁵ M and Kw = [H⁺][OH⁻] = 10⁻¹⁴, so [OH⁻] = 10⁻⁹ M.
A) 5 M is not a concentration derived from pH calculations.
B) 10⁻⁵ M is the [H⁺] concentration, not [OH⁻].
D) 10⁻¹ M would correspond to pOH = 1.
Question 8
What is a buffer?
A) A solution that prevents any pH change from occurring
B) A solution that resists changes in pH when small amounts of acid or
base are added
C) A solution with a pH of exactly 7.0
D) A solution that contains only weak acids
Module 1-8 Exams & Final Exam
Comprehensive Review Questions with
Answers & Rationales
Question 1
Which of the following best defines organic chemistry?
A) The study of all carbon-containing compounds
B) The study of compounds containing carbon-hydrogen bonds
C) The study of compounds found only in living organisms
D) The study of compounds that contain oxygen
Correct Answer: B) The study of compounds containing carbon-
hydrogen bonds
Rationale: Organic chemistry is defined as the study of carbon-containing
compounds, specifically those with carbon-hydrogen (C-H) bonds. Inorganic
compounds may contain carbon (e.g., carbon dioxide, carbonates) but lack C-H
bonds.
A) Not all carbon-containing compounds are organic (e.g., CO₂, carbonates).
C) Organic compounds can be synthesized in the laboratory and are not
limited to living organisms.
D) Many organic compounds lack oxygen (e.g., hydrocarbons).
Question 2
Which scientist is credited with first synthesizing an organic compound from
inorganic starting materials, disproving vitalism?
A) Louis Pasteur
B) Friedrich Wöhler
C) August Kekulé
D) Linus Pauling
,Correct Answer: B) Friedrich Wöhler
Rationale: In 1828, Friedrich Wöhler synthesized urea (an organic
compound) from ammonium cyanate (an inorganic compound),
demonstrating that organic compounds could be created in the laboratory
without a "vital force."
A) Pasteur worked on fermentation and stereochemistry.
C) Kekulé proposed the structure of benzene.
D) Pauling worked on chemical bonding and protein structure.
Question 3
What are the four most abundant elements found in living organisms?
A) Carbon, Hydrogen, Oxygen, Nitrogen
B) Carbon, Hydrogen, Oxygen, Sodium
C) Carbon, Nitrogen, Oxygen, Phosphorus
D) Carbon, Hydrogen, Nitrogen, Sulfur
Correct Answer: A) Carbon, Hydrogen, Oxygen, Nitrogen
Rationale: These four elements make up approximately 96% of the mass of
most living organisms. They are considered "bulk elements" and form the
backbone of all major biomolecules: carbohydrates (C, H, O), proteins (C, H, O,
N, S), lipids (C, H, O), and nucleic acids (C, H, O, N, P).
B) Sodium is a trace element, not among the four most abundant.
C) Phosphorus is important but not among the top four by abundance.
D) Sulfur is present in some amino acids but is not among the top four.
Question 4
Which statement correctly describes water's role in biological systems?
A) Water is a poor solvent for charged molecules
B) Water can make up to 85% of a living organism's mass
C) Water is considered a non-polar solvent
D) Water molecules cannot form hydrogen bonds
,Correct Answer: B) Water can make up to 85% of a living organism's
mass
Rationale: Water is known as the "medium of life." In many organisms, water
constitutes 70-85% of total mass. Its polar nature allows it to serve as an
excellent solvent for ions and polar molecules. Water's ability to form
hydrogen bonds is critical for its unique properties.
A) Water is an excellent solvent for charged (polar) molecules and ions.
C) Water is a polar solvent due to its uneven charge distribution.
D) Water molecules readily form hydrogen bonds with other water molecules
and polar solutes.
Question 5
Which of the following is NOT a function of carbohydrates in cells?
A) Energy source for cells
B) Structural role in RNA
C) Structural role in DNA
D) Basis for building proteins
Correct Answer: D) Basis for building proteins
Rationale: Proteins are built from amino acids, not carbohydrates.
Carbohydrates serve as energy sources (glucose), structural components
(cellulose in plants, ribose in RNA/DNA), and metabolic intermediates. They
do not serve as the building blocks for protein synthesis.
A) Glucose is the primary energy source for most cells.
B) Ribose is a carbohydrate component of RNA.
C) Deoxyribose is a carbohydrate component of DNA.
Question 6
What is the pH of a solution with a hydrogen ion concentration of 1 × 10−7 M?
A) 5.0
B) 7.0
, C) 9.0
D) 1.0
Correct Answer: B) 7.0
Rationale: pH = -log[H⁺]. When [H⁺] = 1 × 10−7 M, pH = -log(10⁻⁷) = 7.0. Pure
water at 25°C has a pH of 7.0, which is neutral. Solutions with pH < 7 are
acidic; pH > 7 are basic.
A) pH 5.0 corresponds to [H⁺] = 1 × 10−5 M.
C) pH 9.0 corresponds to [H⁺] = 1 × 10−9 M.
D) pH 1.0 corresponds to [H⁺] = 1 × 10−1 M.
Question 7
A solution has a pH = 5.0. What is the concentration of OH⁻ in M?
A) 5 M
B) 10−5 M
C) 10−9 M
D) 10−1 M
Correct Answer: C) 10−9 M
Rationale: At 25°C, pH + pOH = 14. If pH = 5.0, then pOH = 9.0. [OH⁻] = 10⁻⁹
M. Alternatively, [H⁺] = 10⁻⁵ M and Kw = [H⁺][OH⁻] = 10⁻¹⁴, so [OH⁻] = 10⁻⁹ M.
A) 5 M is not a concentration derived from pH calculations.
B) 10⁻⁵ M is the [H⁺] concentration, not [OH⁻].
D) 10⁻¹ M would correspond to pOH = 1.
Question 8
What is a buffer?
A) A solution that prevents any pH change from occurring
B) A solution that resists changes in pH when small amounts of acid or
base are added
C) A solution with a pH of exactly 7.0
D) A solution that contains only weak acids
