Biochemistry 6th Edition Garrett Test Bank (All
Chapters 1-32 Complete) Questions & Answers
with rationales 2026
1. Which of the following attributes is a definitive characteristic of all living organisms?
A) The ability to move mechanically through space
B) A high degree of chemical complexity and microscopic organization
C) The utilization of silicon as a structural backbone
D) Complete independence from thermodynamic laws
Answer: B) A high degree of chemical complexity and microscopic organization
Rationale: Living organisms possess intricate internal structures, thousands of different proteins, and
precise cellular organization. Movements, alternative backbones like silicon, or defying
thermodynamics are either not universal or physically impossible.
2. Biological macromolecules are primarily constructed from which group of elements?
A) Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
B) Carbon, silicon, sodium, potassium, and chlorine
C) Nitrogen, oxygen, iron, copper, and zinc
D) Hydrogen, helium, carbon, and oxygen
Answer: A) Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
Rationale: These six elements, often abbreviated as CHNOPS, make up over 97% of the mass of most
organisms and constitute the building blocks of proteins, lipids, carbohydrates, and nucleic acids.
3. What is the primary thermodynamic driving force that allows non-spontaneous synthetic reactions
to occur in living cells?
A) Earth's magnetic field
B) Coupling with highly exergonic metabolic reactions
C) The continuous lowering of external environmental entropy
D) Spontaneous heat absorption from the vacuum of space
Answer: B) Coupling with highly exergonic metabolic reactions
Rationale: Cells drive endergonic (non-spontaneous) processes by coupling them directly to highly
exergonic (spontaneous) reactions, typically via the hydrolysis of high-energy phosphate bonds in ATP.
,4. If a chemical reaction has a Δ G° > 0, what can be inferred about the reaction under standard
conditions?
A) It will proceed rapidly in the forward direction.
B) It releases heat into the surroundings.
C) It is endergonic and requires an input of energy to proceed forward.
D) It is at perfect dynamic equilibrium.
Answer: C) It is endergonic and requires an input of energy to proceed forward.
Rationale: A positive standard free energy change (Δ G° > 0) denotes an endergonic process. It is non-
spontaneous under standard conditions and must absorb free energy to move forward.
5. How do enzymes accelerate the rates of cellular chemical reactions?
A) By changing the net equilibrium constant (\(K_{eq}\)) of the reaction
B) By lowering the activation energy (\(\Delta G^\ddagger\)) required for the transition state
C) By adding thermal energy directly into the substrate molecules
D) By making a non-spontaneous reaction spontaneous
Answer: B) By lowering the activation energy (\(\Delta G^\ddagger\)) required for the transition state
Rationale: Enzymes accelerate reaction rates by stabilizing the transition state and decreasing the
activation energy barrier. They cannot alter the overall free energy change (Δ G) or shift the chemical
equilibrium position.
Chapter 2: Water: The Medium of Life
6. Which physical property of water allows it to remain liquid over a wide temperature range and act
as an effective thermal buffer?
A) Its low molecular weight
B) Its highly linear molecular geometry
C) Its extensive network of intermolecular hydrogen bonds
D) Its low heat of vaporization
Answer: C) Its extensive network of intermolecular hydrogen bonds
Rationale: Each water molecule can form up to four hydrogen bonds with neighboring molecules. This
cohesive network requires significant thermal energy to disrupt, leading to high specific heat, high
boiling point, and excellent thermal buffering.
7. Why are non-polar molecules like hydrocarbons poorly soluble in water?
A) Water molecules form strong covalent bonds with non-polar solutes.
B) Non-polar molecules actively break the intramolecular covalent bonds of water.
C) Water molecules must organize into a highly ordered, cage-like structure around them, reducing
systemic entropy.
D) Non-polar substances neutralize the electrical dipole moment of water.
,Answer: C) Water molecules must organize into a highly ordered, cage-like structure around them,
reducing systemic entropy.
Rationale: The hydrophobic effect is driven by thermodynamics. When non-polar substances are
introduced, water molecules form an ordered clathrate cage around them. This drop in water entropy
is unfavorable, causing non-polar molecules to aggregate to minimize exposed surface area.
8. What is the actual pH of an aqueous solution that contains a hydrogen ion concentration \([H^+]\)
of 3.2 × 10⁻⁶ M?
A) 6.00
B) 5.49
C) 6.51
D) 7.40
Answer: B) 5.49
Rationale: Using the standard operational definition of pH, we calculate: \(\text{pH} = -\log_{10}[H^+]
= -\log_{10}(3.2 \times 10^{-6}) = 6 - \log_{10}(3.2) \approx 6 - 0.51 = 5.49\).
9. According to the Henderson-Hasselbalch equation, when the concentration of a weak acid
(\([HA]\)) is exactly equal to its conjugate base (\([A^-]\)), what is the relationship between pH and
\(pK_{a}\)?
A) \(\text{pH} = \text{p}K_a + 1\)
B) \(\text{pH} = \frac{1}{2}\text{p}K_a\)
C) \(\text{pH} = \text{p}K_a\)
D) \(\text{pH} = 14 - \text{p}K_a\)
Answer: C) pH = pK_a
Rationale: The equation states \(\text{pH} = \text{p}K_a + \log([A^-]/[HA])\). If \([A^-] = [HA]\), the
ratio is 1, and since \(\log(1) = 0\), the expression simplifies cleanly to \(\text{pH} = \text{p}K_a\).
10. A buffer system functions most effectively against changes in pH within which range?
A) Exactly at pH 7.00 regardless of the acid used
B) Within one pH unit above or below the \(pK_{a}\) of the weak acid
C) Between pH 1.0 and 3.0 for all biological compounds
D) Only when the solution is entirely composed of conjugate base
Answer: B) Within one pH unit above or below the pK_a of the weak acid
Rationale: A buffer works best when there are significant and comparable amounts of both the weak
acid and its conjugate base present to neutralize added bases or acids. This optimal zone occurs within
± 1 unit of the system's \(\text{p}K_a\).
Chapter 3: Amino Acids
, 11. Which of the standard 20 amino acids lacks a chiral (α-carbon) center?
A) Alanine
B) Proline
C) Glycine
D) Tryptophan
Answer: C) Glycine
Rationale: Glycine’s side chain is a single hydrogen atom. Because the α-carbon is bonded to two
identical hydrogen atoms, it is symmetric and therefore lacks a chiral center.
12. Which amino acid contains a secondary amino group locked within a rigid five-membered ring
structure, severely limiting polypeptide conformational flexibility?
A) Phenylalanine
B) Proline
C) Histidine
D) Isoleucine
Answer: B) Proline
Rationale: Proline contains an aliphatic side chain that cycles back and covalently bonds to the
nitrogen of the amino group, forming a rigid pyrrolidine ring that constrains peptide backbone
rotation.
13. Which group of amino acids possesses side chains that absorb ultraviolet light strongly at a
wavelength of 280 nm?
A) Serine, Threonine, and Cysteine
B) Arginine, Lysine, and Histidine
C) Phenylalanine, Tyrosine, and Tryptophan
D) Alanine, Valine, and Leucine
Answer: C) Phenylalanine, Tyrosine, and Tryptophan
Rationale: These are aromatic amino acids. The delocalized π electrons within their conjugated ring
structures absorb UV light at 280 nm, a property frequently exploited to quantify protein
concentrations.
14. What is the net charge of the amino acid Glutamic Acid (side chain \(pK_a \approx 4.2\)) when
dissolved in a solution buffered tightly at pH 7.0?
A) +1
B) 0
C) -1
D) -2
Answer: C) -1
Rationale: At pH 7.0, the α-carboxyl group (-) is deprotonated, the α-amino group (+) is protonated,
Chapters 1-32 Complete) Questions & Answers
with rationales 2026
1. Which of the following attributes is a definitive characteristic of all living organisms?
A) The ability to move mechanically through space
B) A high degree of chemical complexity and microscopic organization
C) The utilization of silicon as a structural backbone
D) Complete independence from thermodynamic laws
Answer: B) A high degree of chemical complexity and microscopic organization
Rationale: Living organisms possess intricate internal structures, thousands of different proteins, and
precise cellular organization. Movements, alternative backbones like silicon, or defying
thermodynamics are either not universal or physically impossible.
2. Biological macromolecules are primarily constructed from which group of elements?
A) Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
B) Carbon, silicon, sodium, potassium, and chlorine
C) Nitrogen, oxygen, iron, copper, and zinc
D) Hydrogen, helium, carbon, and oxygen
Answer: A) Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
Rationale: These six elements, often abbreviated as CHNOPS, make up over 97% of the mass of most
organisms and constitute the building blocks of proteins, lipids, carbohydrates, and nucleic acids.
3. What is the primary thermodynamic driving force that allows non-spontaneous synthetic reactions
to occur in living cells?
A) Earth's magnetic field
B) Coupling with highly exergonic metabolic reactions
C) The continuous lowering of external environmental entropy
D) Spontaneous heat absorption from the vacuum of space
Answer: B) Coupling with highly exergonic metabolic reactions
Rationale: Cells drive endergonic (non-spontaneous) processes by coupling them directly to highly
exergonic (spontaneous) reactions, typically via the hydrolysis of high-energy phosphate bonds in ATP.
,4. If a chemical reaction has a Δ G° > 0, what can be inferred about the reaction under standard
conditions?
A) It will proceed rapidly in the forward direction.
B) It releases heat into the surroundings.
C) It is endergonic and requires an input of energy to proceed forward.
D) It is at perfect dynamic equilibrium.
Answer: C) It is endergonic and requires an input of energy to proceed forward.
Rationale: A positive standard free energy change (Δ G° > 0) denotes an endergonic process. It is non-
spontaneous under standard conditions and must absorb free energy to move forward.
5. How do enzymes accelerate the rates of cellular chemical reactions?
A) By changing the net equilibrium constant (\(K_{eq}\)) of the reaction
B) By lowering the activation energy (\(\Delta G^\ddagger\)) required for the transition state
C) By adding thermal energy directly into the substrate molecules
D) By making a non-spontaneous reaction spontaneous
Answer: B) By lowering the activation energy (\(\Delta G^\ddagger\)) required for the transition state
Rationale: Enzymes accelerate reaction rates by stabilizing the transition state and decreasing the
activation energy barrier. They cannot alter the overall free energy change (Δ G) or shift the chemical
equilibrium position.
Chapter 2: Water: The Medium of Life
6. Which physical property of water allows it to remain liquid over a wide temperature range and act
as an effective thermal buffer?
A) Its low molecular weight
B) Its highly linear molecular geometry
C) Its extensive network of intermolecular hydrogen bonds
D) Its low heat of vaporization
Answer: C) Its extensive network of intermolecular hydrogen bonds
Rationale: Each water molecule can form up to four hydrogen bonds with neighboring molecules. This
cohesive network requires significant thermal energy to disrupt, leading to high specific heat, high
boiling point, and excellent thermal buffering.
7. Why are non-polar molecules like hydrocarbons poorly soluble in water?
A) Water molecules form strong covalent bonds with non-polar solutes.
B) Non-polar molecules actively break the intramolecular covalent bonds of water.
C) Water molecules must organize into a highly ordered, cage-like structure around them, reducing
systemic entropy.
D) Non-polar substances neutralize the electrical dipole moment of water.
,Answer: C) Water molecules must organize into a highly ordered, cage-like structure around them,
reducing systemic entropy.
Rationale: The hydrophobic effect is driven by thermodynamics. When non-polar substances are
introduced, water molecules form an ordered clathrate cage around them. This drop in water entropy
is unfavorable, causing non-polar molecules to aggregate to minimize exposed surface area.
8. What is the actual pH of an aqueous solution that contains a hydrogen ion concentration \([H^+]\)
of 3.2 × 10⁻⁶ M?
A) 6.00
B) 5.49
C) 6.51
D) 7.40
Answer: B) 5.49
Rationale: Using the standard operational definition of pH, we calculate: \(\text{pH} = -\log_{10}[H^+]
= -\log_{10}(3.2 \times 10^{-6}) = 6 - \log_{10}(3.2) \approx 6 - 0.51 = 5.49\).
9. According to the Henderson-Hasselbalch equation, when the concentration of a weak acid
(\([HA]\)) is exactly equal to its conjugate base (\([A^-]\)), what is the relationship between pH and
\(pK_{a}\)?
A) \(\text{pH} = \text{p}K_a + 1\)
B) \(\text{pH} = \frac{1}{2}\text{p}K_a\)
C) \(\text{pH} = \text{p}K_a\)
D) \(\text{pH} = 14 - \text{p}K_a\)
Answer: C) pH = pK_a
Rationale: The equation states \(\text{pH} = \text{p}K_a + \log([A^-]/[HA])\). If \([A^-] = [HA]\), the
ratio is 1, and since \(\log(1) = 0\), the expression simplifies cleanly to \(\text{pH} = \text{p}K_a\).
10. A buffer system functions most effectively against changes in pH within which range?
A) Exactly at pH 7.00 regardless of the acid used
B) Within one pH unit above or below the \(pK_{a}\) of the weak acid
C) Between pH 1.0 and 3.0 for all biological compounds
D) Only when the solution is entirely composed of conjugate base
Answer: B) Within one pH unit above or below the pK_a of the weak acid
Rationale: A buffer works best when there are significant and comparable amounts of both the weak
acid and its conjugate base present to neutralize added bases or acids. This optimal zone occurs within
± 1 unit of the system's \(\text{p}K_a\).
Chapter 3: Amino Acids
, 11. Which of the standard 20 amino acids lacks a chiral (α-carbon) center?
A) Alanine
B) Proline
C) Glycine
D) Tryptophan
Answer: C) Glycine
Rationale: Glycine’s side chain is a single hydrogen atom. Because the α-carbon is bonded to two
identical hydrogen atoms, it is symmetric and therefore lacks a chiral center.
12. Which amino acid contains a secondary amino group locked within a rigid five-membered ring
structure, severely limiting polypeptide conformational flexibility?
A) Phenylalanine
B) Proline
C) Histidine
D) Isoleucine
Answer: B) Proline
Rationale: Proline contains an aliphatic side chain that cycles back and covalently bonds to the
nitrogen of the amino group, forming a rigid pyrrolidine ring that constrains peptide backbone
rotation.
13. Which group of amino acids possesses side chains that absorb ultraviolet light strongly at a
wavelength of 280 nm?
A) Serine, Threonine, and Cysteine
B) Arginine, Lysine, and Histidine
C) Phenylalanine, Tyrosine, and Tryptophan
D) Alanine, Valine, and Leucine
Answer: C) Phenylalanine, Tyrosine, and Tryptophan
Rationale: These are aromatic amino acids. The delocalized π electrons within their conjugated ring
structures absorb UV light at 280 nm, a property frequently exploited to quantify protein
concentrations.
14. What is the net charge of the amino acid Glutamic Acid (side chain \(pK_a \approx 4.2\)) when
dissolved in a solution buffered tightly at pH 7.0?
A) +1
B) 0
C) -1
D) -2
Answer: C) -1
Rationale: At pH 7.0, the α-carboxyl group (-) is deprotonated, the α-amino group (+) is protonated,
