, CHAPTER LIST
Chapter 1: Chemical Composition of Living Beings
Chapter 2: Water
Chapter 3: Proteins
Chapter 4: Carbohydrates
Chapter 5: Lipids
Chapter 6: Nucleic Acids
Chapter 7: Elements of Thermodynamics and Biochemical Kinetics
Chapter 8: Enzymes
Chapter 9: Biological Oxidations: Bioenergetics
Chapter 10: Antioxidants
Chapter 11: Membranes
Chapter 12: Digestion - Absorption
Chapter 13: Metabolism
Chapter 14: Carbohydrate Metabolism
Chapter 15: Lipid Metabolism
Chapter 16: Amino Acid Metabolism
Chapter 17: Heme Metabolism
Chapter 18: Purine and Pyrimidine Metabolism
Chapter 19: Integration and Regulation of Metabolism
Chapter 20: Metabolism in Some Tissues
Chapter 21: The Genetic Information (I)
Chapter 22: The Genetic Information (II)
Chapter 23: Regulation of Gene Expression
Chapter 24: Posttranslational Protein Modifications
Chapter 25: Biochemical Basis of Endocrinology (I) Receptors and Signal
Transduction
Chapter 26: Biochemical Bases of Endocrinology (II) Hormones and Other
Chemical Intermediates
Chapter 27: Vitamins
Chapter 28: Water and Acid–Base Balance
Chapter 29: Essential Minerals
Chapter 30: Molecular Basis of Immunity
Chapter 31: Hemostasis
Chapter 32: Cell Death
,Chapter 1: Chemical Composition of Living Beings
Multiple Choice
Question 1
Which element is classified as an essential trace element in the human body rather than
a major bulk element?
A. Zinc
B. Calcium
C. Phosphorus
D. Sulfur
Answer: A.
Rationale: Essential trace elements, such as zinc, iron, copper, and manganese, are
required by the human body in minute quantities (micrograms to milligrams per day)
where they function primarily as enzyme cofactors or structural components of proteins.
In contrast, bulk elements like calcium, phosphorus, sulfur, carbon, hydrogen, oxygen,
and nitrogen constitute the vast majority of human body mass and structural
framework.
Question 2
What is the primary biological reason that total body water percentage is significantly
higher in newborns (approximately 75–80%) compared to elderly adults (approximately
45–50%)?
A. Higher proportion of adipose tissue relative to lean body mass in newborns
B. Greater proportion of extracellular fluid volume and lower fat mass in newborns
C. Inability of newborn kidneys to excrete excess water during early development
D. Increased concentration of intracellular structural glycogen in neonatal tissues
,Answer: B.
Rationale: Infant tissues possess a significantly lower percentage of body fat and a
expanded extracellular fluid compartment relative to total body mass. Because adipose
tissue contains very low water content (~10%) compared to lean muscle mass (~75%),
the higher ratio of lean tissue and extracellular volume in infants accounts for their total
body water constituting nearly 75–80% of body mass, whereas aging is accompanied by
increased adiposity and decreased lean tissue mass, lowering total body water.
Question 3
Which chemical property of carbon makes it uniquely suited as the central backbone
element for complex organic biomolecules compared to other Group 14 elements like
silicon?
A. Ability to form stable, high-energy ionic bonds with transition metals in aqueous
solution
B. Spontaneous oxidation in water that provides free energy to drive biochemical
pathways
C. Ability to form strong, stable covalent single and double bonds with itself and other
nonmetals in water
D. Formation of insoluble polymeric silicates that maintain fixed cellular structures
Answer: C.
Rationale: Carbon's tetravalency, moderate electronegativity, and small atomic radius
allow it to form strong, stable covalent single, double, and triple bonds with itself and
with oxygen, nitrogen, hydrogen, and sulfur. Unlike silicon-silicon bonds, which are
unstable in the presence of water and oxygen, carbon-carbon bonds remain
thermodynamically stable in aqueous physiological environments, allowing the
construction of diverse, complex linear, branched, and cyclic macromolecular
architectures.
Question 4
Which functional group confers both polar solubility and acidic properties to amino
acids and fatty acids at physiological pH?
A. Hydroxyl group
,B. Amino group
C. Sulfhydryl group
D. Carboxyl group
Answer: D.
Rationale: The carboxyl group (-COOH) acts as a weak acid that readily ionizes at
physiological pH (~7.4) to yield a negatively charged carboxylate anion (-COO⁻) and a
free proton. This ionization imparts negative charge, increases hydrogen-bonding
capability with water molecules, and raises overall aqueous solubility for carboxylic
acids, amino acids, and fatty acid derivatives.
Question 5
How does the hydrophobic effect drive the spontaneous folding of globular proteins in
an aqueous cellular environment?
A. Clustering of nonpolar side chains in the interior decreases water ordering, increasing
system entropy.
B. Nonpolar side chains form covalent ester bonds with water molecules, releasing free
energy.
C. Polar side chains are repelled into the interior of the protein by dissolved inorganic
salts.
D. Hydrophobic interactions increase the total heat capacity of the solvent through ionic
bond formation.
Answer: A.
Rationale: When nonpolar amino acid side chains are exposed to water, water
molecules are forced to form structured, cage-like clathrate shells around them, which
represents an thermodynamically unfavorable decrease in water entropy. When
nonpolar side chains collapse into the protein's interior, these structured water
molecules are released into the bulk solvent, causing a major increase in universal
entropy (Δ S > 0) that thermodynamically favors native protein folding.
Question 6
,Why does the high dielectric constant of water facilitate the dissolution of inorganic
salts such as sodium chloride?
A. Water molecules form strong covalent linkages with dissolved sodium and chloride
ions.
B. Water reduces the electrostatic attractive forces between oppositely charged ions
through hydration shells.
C. Water neutralizes the electric charge of ions by transferring protons directly to salt
crystals.
D. Water forces dissolved ions into a highly ordered crystalline lattice within the
intracellular fluid.
Answer: B.
Rationale: Water has a very high dielectric constant (~80 at 20°C) due to its polar
nature and permanent dipole moment. According to Coulomb's Law, a high dielectric
constant drastically screens and weakens the electrostatic attraction between cations
(Na⁺) and anions (Cl⁻). Orienting water dipoles around the individual ions forms
hydration shells, stabilizing the separated ions in aqueous solution.
Question 7
How does an increase in the proportion of adipose tissue affect total body water
percentage and drug distribution in an individual?
A. Total body water percentage increases, expanding the distribution volume of
hydrophilic drugs.
B. Total body water percentage remains unchanged, but intracellular potassium
concentration doubles.
C. Total body water percentage decreases, reducing the distribution volume of
hydrophilic drugs.
D. Total body water percentage decreases, eliminating the clearance of lipid-soluble
compounds.
Answer: C.
,Rationale: Adipose tissue is hydrophobic and contains very little water (~10%)
compared to lean muscular tissue (~75%). Individuals with higher body fat composition
have a significantly lower total body water percentage relative to total mass.
Consequently, hydrophilic (water-soluble) medications distribute into a smaller volume
of total body water, resulting in higher plasma concentration per dose compared to
leaner individuals.
Question 8
Why are infants at a substantially higher risk of rapid metabolic decompensation from
acute fluid loss (e.g., severe vomiting or diarrhea) than adults?
A. Infants possess a lower total body water percentage and a smaller renal filtration
capacity.
B. Infant intracellular fluid volume is twice as large as extracellular fluid volume,
preventing fluid shifts.
C. Infant adipose tissue rapidly synthesizes metabolic water to dilute remaining plasma
electrolytes.
D. Infants have a higher metabolic rate and a larger surface-area-to-volume ratio,
accelerating fluid turnover.
Answer: D.
Rationale: Infants exhibit a significantly higher basal metabolic rate and body surface
area relative to body weight compared to adults, leading to much higher daily fluid
turnover rates. Because a larger fraction of their total body water resides in the
vulnerable extracellular fluid compartment, rapid gastrointestinal fluid loss depletes
extracellular volume quickly, exceeding renal compensatory capacity and causing rapid
dehydration and electrolyte imbalance.
Question 9
A patient experiences severe intravascular fluid loss following acute hemorrhage. Which
physiological fluid redistribution is expected to occur immediately across body fluid
compartments?
A. Water shifts from the intracellular compartment to the interstitial and intravascular
spaces to restore vascular volume.
, B. Electrolytes move out of the vascular space into the intracellular space to increase
intracellular osmotic pressure.
C. Proteins move rapidly out of muscle cells into the blood plasma to increase oncotic
pressure without water movement.
D. Water moves from the extracellular compartment into fat cells to protect lipid stores
from oxidation.
Answer: A.
Rationale: Loss of intravascular volume reduces hydrostatic pressure in the systemic
capillaries. To maintain hemodynamic stability, water moves along hydrostatic and
osmotic gradients from the interstitial fluid into the vascular bed, followed by water
shifting from the intracellular fluid compartment into the extracellular space to equalize
osmotic gradients, thereby buffering vascular volume contraction.
Question 10
If a toxic heavy metal such as lead replaces essential zinc ions within zinc-finger protein
motifs, what is the immediate molecular consequence on protein function?
A. Enhanced covalent binding of the protein to the major groove of target double-
stranded DNA
B. Disruption of tertiary structure coordination, leading to loss of specific DNA-binding
capability
C. Immediate cleavage of peptide bonds adjacent to histidine residues throughout the
protein
D. Conversion of the zinc-finger motif into an active catalytic site for carbohydrate
hydrolysis
Answer: B.
Rationale: Zinc-finger motifs rely specifically on the precise coordination of a Zn²⁺ ion
by cysteine and histidine side chains to stabilize a compact tertiary structure essential
for binding specific DNA sequences. Lead (Pb²⁺) or cadmium (Cd²⁺) substitution alters
ionic radius and coordination geometry, causing misfolding of the motif, loss of specific
nucleic acid binding, and widespread transcriptional dysregulation.
Chapter 1: Chemical Composition of Living Beings
Chapter 2: Water
Chapter 3: Proteins
Chapter 4: Carbohydrates
Chapter 5: Lipids
Chapter 6: Nucleic Acids
Chapter 7: Elements of Thermodynamics and Biochemical Kinetics
Chapter 8: Enzymes
Chapter 9: Biological Oxidations: Bioenergetics
Chapter 10: Antioxidants
Chapter 11: Membranes
Chapter 12: Digestion - Absorption
Chapter 13: Metabolism
Chapter 14: Carbohydrate Metabolism
Chapter 15: Lipid Metabolism
Chapter 16: Amino Acid Metabolism
Chapter 17: Heme Metabolism
Chapter 18: Purine and Pyrimidine Metabolism
Chapter 19: Integration and Regulation of Metabolism
Chapter 20: Metabolism in Some Tissues
Chapter 21: The Genetic Information (I)
Chapter 22: The Genetic Information (II)
Chapter 23: Regulation of Gene Expression
Chapter 24: Posttranslational Protein Modifications
Chapter 25: Biochemical Basis of Endocrinology (I) Receptors and Signal
Transduction
Chapter 26: Biochemical Bases of Endocrinology (II) Hormones and Other
Chemical Intermediates
Chapter 27: Vitamins
Chapter 28: Water and Acid–Base Balance
Chapter 29: Essential Minerals
Chapter 30: Molecular Basis of Immunity
Chapter 31: Hemostasis
Chapter 32: Cell Death
,Chapter 1: Chemical Composition of Living Beings
Multiple Choice
Question 1
Which element is classified as an essential trace element in the human body rather than
a major bulk element?
A. Zinc
B. Calcium
C. Phosphorus
D. Sulfur
Answer: A.
Rationale: Essential trace elements, such as zinc, iron, copper, and manganese, are
required by the human body in minute quantities (micrograms to milligrams per day)
where they function primarily as enzyme cofactors or structural components of proteins.
In contrast, bulk elements like calcium, phosphorus, sulfur, carbon, hydrogen, oxygen,
and nitrogen constitute the vast majority of human body mass and structural
framework.
Question 2
What is the primary biological reason that total body water percentage is significantly
higher in newborns (approximately 75–80%) compared to elderly adults (approximately
45–50%)?
A. Higher proportion of adipose tissue relative to lean body mass in newborns
B. Greater proportion of extracellular fluid volume and lower fat mass in newborns
C. Inability of newborn kidneys to excrete excess water during early development
D. Increased concentration of intracellular structural glycogen in neonatal tissues
,Answer: B.
Rationale: Infant tissues possess a significantly lower percentage of body fat and a
expanded extracellular fluid compartment relative to total body mass. Because adipose
tissue contains very low water content (~10%) compared to lean muscle mass (~75%),
the higher ratio of lean tissue and extracellular volume in infants accounts for their total
body water constituting nearly 75–80% of body mass, whereas aging is accompanied by
increased adiposity and decreased lean tissue mass, lowering total body water.
Question 3
Which chemical property of carbon makes it uniquely suited as the central backbone
element for complex organic biomolecules compared to other Group 14 elements like
silicon?
A. Ability to form stable, high-energy ionic bonds with transition metals in aqueous
solution
B. Spontaneous oxidation in water that provides free energy to drive biochemical
pathways
C. Ability to form strong, stable covalent single and double bonds with itself and other
nonmetals in water
D. Formation of insoluble polymeric silicates that maintain fixed cellular structures
Answer: C.
Rationale: Carbon's tetravalency, moderate electronegativity, and small atomic radius
allow it to form strong, stable covalent single, double, and triple bonds with itself and
with oxygen, nitrogen, hydrogen, and sulfur. Unlike silicon-silicon bonds, which are
unstable in the presence of water and oxygen, carbon-carbon bonds remain
thermodynamically stable in aqueous physiological environments, allowing the
construction of diverse, complex linear, branched, and cyclic macromolecular
architectures.
Question 4
Which functional group confers both polar solubility and acidic properties to amino
acids and fatty acids at physiological pH?
A. Hydroxyl group
,B. Amino group
C. Sulfhydryl group
D. Carboxyl group
Answer: D.
Rationale: The carboxyl group (-COOH) acts as a weak acid that readily ionizes at
physiological pH (~7.4) to yield a negatively charged carboxylate anion (-COO⁻) and a
free proton. This ionization imparts negative charge, increases hydrogen-bonding
capability with water molecules, and raises overall aqueous solubility for carboxylic
acids, amino acids, and fatty acid derivatives.
Question 5
How does the hydrophobic effect drive the spontaneous folding of globular proteins in
an aqueous cellular environment?
A. Clustering of nonpolar side chains in the interior decreases water ordering, increasing
system entropy.
B. Nonpolar side chains form covalent ester bonds with water molecules, releasing free
energy.
C. Polar side chains are repelled into the interior of the protein by dissolved inorganic
salts.
D. Hydrophobic interactions increase the total heat capacity of the solvent through ionic
bond formation.
Answer: A.
Rationale: When nonpolar amino acid side chains are exposed to water, water
molecules are forced to form structured, cage-like clathrate shells around them, which
represents an thermodynamically unfavorable decrease in water entropy. When
nonpolar side chains collapse into the protein's interior, these structured water
molecules are released into the bulk solvent, causing a major increase in universal
entropy (Δ S > 0) that thermodynamically favors native protein folding.
Question 6
,Why does the high dielectric constant of water facilitate the dissolution of inorganic
salts such as sodium chloride?
A. Water molecules form strong covalent linkages with dissolved sodium and chloride
ions.
B. Water reduces the electrostatic attractive forces between oppositely charged ions
through hydration shells.
C. Water neutralizes the electric charge of ions by transferring protons directly to salt
crystals.
D. Water forces dissolved ions into a highly ordered crystalline lattice within the
intracellular fluid.
Answer: B.
Rationale: Water has a very high dielectric constant (~80 at 20°C) due to its polar
nature and permanent dipole moment. According to Coulomb's Law, a high dielectric
constant drastically screens and weakens the electrostatic attraction between cations
(Na⁺) and anions (Cl⁻). Orienting water dipoles around the individual ions forms
hydration shells, stabilizing the separated ions in aqueous solution.
Question 7
How does an increase in the proportion of adipose tissue affect total body water
percentage and drug distribution in an individual?
A. Total body water percentage increases, expanding the distribution volume of
hydrophilic drugs.
B. Total body water percentage remains unchanged, but intracellular potassium
concentration doubles.
C. Total body water percentage decreases, reducing the distribution volume of
hydrophilic drugs.
D. Total body water percentage decreases, eliminating the clearance of lipid-soluble
compounds.
Answer: C.
,Rationale: Adipose tissue is hydrophobic and contains very little water (~10%)
compared to lean muscular tissue (~75%). Individuals with higher body fat composition
have a significantly lower total body water percentage relative to total mass.
Consequently, hydrophilic (water-soluble) medications distribute into a smaller volume
of total body water, resulting in higher plasma concentration per dose compared to
leaner individuals.
Question 8
Why are infants at a substantially higher risk of rapid metabolic decompensation from
acute fluid loss (e.g., severe vomiting or diarrhea) than adults?
A. Infants possess a lower total body water percentage and a smaller renal filtration
capacity.
B. Infant intracellular fluid volume is twice as large as extracellular fluid volume,
preventing fluid shifts.
C. Infant adipose tissue rapidly synthesizes metabolic water to dilute remaining plasma
electrolytes.
D. Infants have a higher metabolic rate and a larger surface-area-to-volume ratio,
accelerating fluid turnover.
Answer: D.
Rationale: Infants exhibit a significantly higher basal metabolic rate and body surface
area relative to body weight compared to adults, leading to much higher daily fluid
turnover rates. Because a larger fraction of their total body water resides in the
vulnerable extracellular fluid compartment, rapid gastrointestinal fluid loss depletes
extracellular volume quickly, exceeding renal compensatory capacity and causing rapid
dehydration and electrolyte imbalance.
Question 9
A patient experiences severe intravascular fluid loss following acute hemorrhage. Which
physiological fluid redistribution is expected to occur immediately across body fluid
compartments?
A. Water shifts from the intracellular compartment to the interstitial and intravascular
spaces to restore vascular volume.
, B. Electrolytes move out of the vascular space into the intracellular space to increase
intracellular osmotic pressure.
C. Proteins move rapidly out of muscle cells into the blood plasma to increase oncotic
pressure without water movement.
D. Water moves from the extracellular compartment into fat cells to protect lipid stores
from oxidation.
Answer: A.
Rationale: Loss of intravascular volume reduces hydrostatic pressure in the systemic
capillaries. To maintain hemodynamic stability, water moves along hydrostatic and
osmotic gradients from the interstitial fluid into the vascular bed, followed by water
shifting from the intracellular fluid compartment into the extracellular space to equalize
osmotic gradients, thereby buffering vascular volume contraction.
Question 10
If a toxic heavy metal such as lead replaces essential zinc ions within zinc-finger protein
motifs, what is the immediate molecular consequence on protein function?
A. Enhanced covalent binding of the protein to the major groove of target double-
stranded DNA
B. Disruption of tertiary structure coordination, leading to loss of specific DNA-binding
capability
C. Immediate cleavage of peptide bonds adjacent to histidine residues throughout the
protein
D. Conversion of the zinc-finger motif into an active catalytic site for carbohydrate
hydrolysis
Answer: B.
Rationale: Zinc-finger motifs rely specifically on the precise coordination of a Zn²⁺ ion
by cysteine and histidine side chains to stabilize a compact tertiary structure essential
for binding specific DNA sequences. Lead (Pb²⁺) or cadmium (Cd²⁺) substitution alters
ionic radius and coordination geometry, causing misfolding of the motif, loss of specific
nucleic acid binding, and widespread transcriptional dysregulation.
