ASU BIO 181 General Biology I Study Guide, Exam Prep
Notes, Practice Questions & Comprehensive Review Bundle
for Arizona State University Students | Cell Biology,
Genetics, Evolution & Scientific Methods Explained
Question 1: Which of the following best describes the primary function of the mitochondrion
in eukaryotic cells?
A. Synthesis of ribosomal RNA and assembly of ribosomal subunits
B. Modification, sorting, and packaging of proteins for secretion
C. Generation of ATP through oxidative phosphorylation
D. Degradation of damaged organelles via autophagy
CORRECT ANSWER: C. Generation of ATP through oxidative phosphorylation
Rationale: Mitochondria are often referred to as the "powerhouses" of eukaryotic cells because
their inner membrane contains the electron transport chain and ATP synthase complexes that
drive oxidative phosphorylation, producing the majority of cellular ATP. While other organelles
perform the functions listed in options A, B, and D, ATP generation is the defining metabolic
role of mitochondria.
Question 2: In the context of enzyme kinetics, what does the Michaelis constant (Km)
represent?
A. The maximum velocity an enzyme can achieve at saturating substrate concentrations
B. The substrate concentration at which the reaction velocity is half of Vmax
C. The rate constant for the conversion of enzyme-substrate complex to product
D. The pH at which an enzyme exhibits optimal activity
CORRECT ANSWER: B. The substrate concentration at which the reaction velocity is half of
Vmax
Rationale: The Michaelis constant (Km) is a fundamental parameter in enzyme kinetics that
quantifies the affinity of an enzyme for its substrate. A lower Km indicates higher affinity, as
less substrate is needed to reach half-maximal velocity. Vmax (option A) represents maximum
velocity, kcat (option C) is the turnover number, and optimal pH (option D) is a separate
environmental factor.
Question 3: Which stage of cellular respiration produces the greatest amount of ATP per
molecule of glucose?
A. Glycolysis
B. Pyruvate oxidation
C. Citric acid cycle
D. Oxidative phosphorylation
CORRECT ANSWER: D. Oxidative phosphorylation
Rationale: Oxidative phosphorylation, which includes the electron transport chain and
chemiosmosis, generates approximately 26-28 ATP molecules per glucose molecule in
eukaryotes. Glycolysis yields 2 ATP (net), pyruvate oxidation yields no direct ATP, and the citric
acid cycle yields 2 ATP (via GTP). Thus, oxidative phosphorylation accounts for over 90% of ATP
production from glucose catabolism.
Question 4: During meiosis I, homologous chromosomes separate. What is the direct
consequence of this separation?
,A. Sister chromatids are pulled to opposite poles of the cell
B. The chromosome number is reduced from diploid to haploid
C. Crossing over between non-sister chromatids is completed
D. DNA replication occurs prior to chromosome segregation
CORRECT ANSWER: B. The chromosome number is reduced from diploid to haploid
Rationale: Meiosis I is a reductional division where homologous chromosome pairs separate,
resulting in two daughter cells each containing one chromosome from each homologous pair—
thus halving the chromosome number from diploid (2n) to haploid (n). Sister chromatid
separation occurs in meiosis II (option A), crossing over occurs during prophase I (option C), and
DNA replication occurs before meiosis begins (option D).
Question 5: Which of the following statements accurately describes the role of NAD+ in
cellular metabolism?
A. It directly phosphorylates ADP to form ATP during substrate-level phosphorylation
B. It serves as a final electron acceptor in anaerobic respiration
C. It functions as an electron carrier, becoming reduced to NADH during catabolic reactions
D. It catalyzes the hydrolysis of macromolecules into monomers
CORRECT ANSWER: C. It functions as an electron carrier, becoming reduced to NADH during
catabolic reactions
Rationale: NAD+ is a coenzyme that accepts electrons (and a proton) during oxidation reactions
in glycolysis, pyruvate oxidation, and the citric acid cycle, becoming reduced to NADH. NADH
then donates electrons to the electron transport chain. NAD+ does not phosphorylate ADP
(option A), oxygen is the final electron acceptor in aerobic respiration (option B), and
enzymes—not coenzymes like NAD+—catalyze hydrolysis reactions (option D).
Question 6: A researcher observes that a particular gene is expressed only in liver cells and
not in muscle cells of the same organism. Which mechanism most likely explains this cell-
type-specific expression?
A. Differences in the DNA sequence of the gene between cell types
B. Alternative splicing of the primary transcript in different tissues
C. Tissue-specific transcription factors binding to enhancer regions
D. Mutations in the promoter region that occur during cell differentiation
CORRECT ANSWER: C. Tissue-specific transcription factors binding to enhancer regions
Rationale: Cell-type-specific gene expression is primarily regulated at the transcriptional level
through transcription factors that bind to enhancers or silencers. Liver-specific transcription
factors activate genes required for hepatic function, while muscle-specific factors activate
myogenic genes. The DNA sequence of the gene is identical in all somatic cells (option A),
alternative splicing (option B) affects mRNA processing but not initial transcriptional activation,
and promoter mutations (option D) are not a normal regulatory mechanism.
Question 7: In a population of beetles, green coloration is dominant (G) and brown is
recessive (g). If 16% of the population exhibits the brown phenotype, what is the frequency
of the heterozygous genotype assuming Hardy-Weinberg equilibrium?
A. 0.16
B. 0.32
,C. 0.48
D. 0.64
CORRECT ANSWER: C. 0.48
Rationale: Under Hardy-Weinberg equilibrium, the frequency of the recessive phenotype (q²)
equals 0.16, so q = √0.16 = 0.4. Since p + q = 1, p = 0.6. The frequency of heterozygotes is 2pq =
2(0.6)(0.4) = 0.48. This calculation assumes no evolutionary forces are acting on the population.
Question 8: Which of the following best characterizes the fluid mosaic model of the plasma
membrane?
A. A rigid structure composed primarily of cellulose and lignin
B. A phospholipid bilayer with embedded proteins that can move laterally
C. A single layer of phospholipids with carbohydrates attached to the extracellular surface
D. A triple-layered structure with cholesterol forming the central core
CORRECT ANSWER: B. A phospholipid bilayer with embedded proteins that can move laterally
Rationale: The fluid mosaic model, proposed by Singer and Nicolson, describes the plasma
membrane as a dynamic phospholipid bilayer in which proteins are embedded and can diffuse
laterally. Fluidity is maintained by unsaturated fatty acids and cholesterol. Cellulose and lignin
are plant cell wall components (option A), membranes are bilayers not monolayers (option C),
and cholesterol modulates fluidity but does not form a central core (option D).
Question 9: During DNA replication, what is the primary function of DNA ligase?
A. Unwinding the double helix ahead of the replication fork
B. Synthesizing RNA primers to initiate DNA synthesis
C. Joining Okazaki fragments on the lagging strand by catalyzing phosphodiester bonds
D. Proofreading newly synthesized DNA and excising mismatched nucleotides
CORRECT ANSWER: C. Joining Okazaki fragments on the lagging strand by catalyzing
phosphodiester bonds
Rationale: DNA ligase seals nicks in the sugar-phosphate backbone by catalyzing the formation
of phosphodiester bonds between adjacent nucleotides. This is essential for joining Okazaki
fragments on the lagging strand. Helicase unwinds DNA (option A), primase synthesizes RNA
primers (option B), and DNA polymerase performs proofreading (option D).
Question 10: Which of the following processes directly requires ATP hydrolysis to transport
molecules against their concentration gradient?
A. Facilitated diffusion via channel proteins
B. Osmosis of water through aquaporins
C. Primary active transport via the sodium-potassium pump
D. Passive movement of oxygen across the lipid bilayer
CORRECT ANSWER: C. Primary active transport via the sodium-potassium pump
Rationale: Primary active transport directly uses ATP hydrolysis to pump ions against their
electrochemical gradient. The Na+/K+ ATPase hydrolyzes one ATP to export 3 Na+ and import 2
K+. Facilitated diffusion (option A), osmosis (option B), and simple diffusion of gases (option D)
are passive processes that do not require energy input.
Question 11: In photosynthesis, what is the primary role of the light-dependent reactions?
, A. To fix carbon dioxide into organic molecules using the Calvin cycle
B. To generate ATP and NADPH using light energy and water
C. To break down glucose into pyruvate in the stroma of chloroplasts
D. To release oxygen as a byproduct of carbohydrate synthesis
CORRECT ANSWER: B. To generate ATP and NADPH using light energy and water
Rationale: The light-dependent reactions occur in the thylakoid membranes and use light
energy to split water (releasing O₂), generate a proton gradient for ATP synthesis via
chemiosmosis, and reduce NADP+ to NADPH. These products (ATP and NADPH) are then used
in the Calvin cycle (option A) for carbon fixation. Glucose breakdown (option C) describes
glycolysis, not photosynthesis, and oxygen release (option D) is a consequence, not the primary
role.
Question 12: Which of the following best describes the relationship between genotype and
phenotype?
A. Genotype refers to observable traits, while phenotype refers to genetic makeup
B. Phenotype is determined solely by genotype, with no environmental influence
C. Genotype is the genetic constitution of an organism, while phenotype is the observable
expression of that genotype influenced by environment
D. Phenotype can be directly inherited, while genotype must be inferred from breeding
experiments
CORRECT ANSWER: C. Genotype is the genetic constitution of an organism, while phenotype
is the observable expression of that genotype influenced by environment
Rationale: Genotype represents the specific alleles an organism carries, while phenotype
encompasses observable characteristics resulting from genotype-environment interactions.
Option A reverses the definitions. Option B is incorrect because environment can modify
phenotype (e.g., nutrition affecting height). Option D is false because genotype is inherited
directly via gametes.
Question 13: What is the primary selective advantage of sexual reproduction over asexual
reproduction?
A. It requires less energy and time to produce offspring
B. It generates greater genetic diversity among offspring, enhancing adaptability
C. It ensures that all offspring are genetically identical to the parent
D. It allows for faster population growth in stable environments
CORRECT ANSWER: B. It generates greater genetic diversity among offspring, enhancing
adaptability
Rationale: Sexual reproduction combines genetic material from two parents through meiosis
and fertilization, creating novel allele combinations. This genetic variation provides raw
material for natural selection, improving population resilience to changing environments.
Asexual reproduction (options A, C, D) is more efficient but produces clones, limiting adaptive
potential.
Question 14: Which of the following molecules is NOT a component of the eukaryotic cell's
cytoskeleton?
Notes, Practice Questions & Comprehensive Review Bundle
for Arizona State University Students | Cell Biology,
Genetics, Evolution & Scientific Methods Explained
Question 1: Which of the following best describes the primary function of the mitochondrion
in eukaryotic cells?
A. Synthesis of ribosomal RNA and assembly of ribosomal subunits
B. Modification, sorting, and packaging of proteins for secretion
C. Generation of ATP through oxidative phosphorylation
D. Degradation of damaged organelles via autophagy
CORRECT ANSWER: C. Generation of ATP through oxidative phosphorylation
Rationale: Mitochondria are often referred to as the "powerhouses" of eukaryotic cells because
their inner membrane contains the electron transport chain and ATP synthase complexes that
drive oxidative phosphorylation, producing the majority of cellular ATP. While other organelles
perform the functions listed in options A, B, and D, ATP generation is the defining metabolic
role of mitochondria.
Question 2: In the context of enzyme kinetics, what does the Michaelis constant (Km)
represent?
A. The maximum velocity an enzyme can achieve at saturating substrate concentrations
B. The substrate concentration at which the reaction velocity is half of Vmax
C. The rate constant for the conversion of enzyme-substrate complex to product
D. The pH at which an enzyme exhibits optimal activity
CORRECT ANSWER: B. The substrate concentration at which the reaction velocity is half of
Vmax
Rationale: The Michaelis constant (Km) is a fundamental parameter in enzyme kinetics that
quantifies the affinity of an enzyme for its substrate. A lower Km indicates higher affinity, as
less substrate is needed to reach half-maximal velocity. Vmax (option A) represents maximum
velocity, kcat (option C) is the turnover number, and optimal pH (option D) is a separate
environmental factor.
Question 3: Which stage of cellular respiration produces the greatest amount of ATP per
molecule of glucose?
A. Glycolysis
B. Pyruvate oxidation
C. Citric acid cycle
D. Oxidative phosphorylation
CORRECT ANSWER: D. Oxidative phosphorylation
Rationale: Oxidative phosphorylation, which includes the electron transport chain and
chemiosmosis, generates approximately 26-28 ATP molecules per glucose molecule in
eukaryotes. Glycolysis yields 2 ATP (net), pyruvate oxidation yields no direct ATP, and the citric
acid cycle yields 2 ATP (via GTP). Thus, oxidative phosphorylation accounts for over 90% of ATP
production from glucose catabolism.
Question 4: During meiosis I, homologous chromosomes separate. What is the direct
consequence of this separation?
,A. Sister chromatids are pulled to opposite poles of the cell
B. The chromosome number is reduced from diploid to haploid
C. Crossing over between non-sister chromatids is completed
D. DNA replication occurs prior to chromosome segregation
CORRECT ANSWER: B. The chromosome number is reduced from diploid to haploid
Rationale: Meiosis I is a reductional division where homologous chromosome pairs separate,
resulting in two daughter cells each containing one chromosome from each homologous pair—
thus halving the chromosome number from diploid (2n) to haploid (n). Sister chromatid
separation occurs in meiosis II (option A), crossing over occurs during prophase I (option C), and
DNA replication occurs before meiosis begins (option D).
Question 5: Which of the following statements accurately describes the role of NAD+ in
cellular metabolism?
A. It directly phosphorylates ADP to form ATP during substrate-level phosphorylation
B. It serves as a final electron acceptor in anaerobic respiration
C. It functions as an electron carrier, becoming reduced to NADH during catabolic reactions
D. It catalyzes the hydrolysis of macromolecules into monomers
CORRECT ANSWER: C. It functions as an electron carrier, becoming reduced to NADH during
catabolic reactions
Rationale: NAD+ is a coenzyme that accepts electrons (and a proton) during oxidation reactions
in glycolysis, pyruvate oxidation, and the citric acid cycle, becoming reduced to NADH. NADH
then donates electrons to the electron transport chain. NAD+ does not phosphorylate ADP
(option A), oxygen is the final electron acceptor in aerobic respiration (option B), and
enzymes—not coenzymes like NAD+—catalyze hydrolysis reactions (option D).
Question 6: A researcher observes that a particular gene is expressed only in liver cells and
not in muscle cells of the same organism. Which mechanism most likely explains this cell-
type-specific expression?
A. Differences in the DNA sequence of the gene between cell types
B. Alternative splicing of the primary transcript in different tissues
C. Tissue-specific transcription factors binding to enhancer regions
D. Mutations in the promoter region that occur during cell differentiation
CORRECT ANSWER: C. Tissue-specific transcription factors binding to enhancer regions
Rationale: Cell-type-specific gene expression is primarily regulated at the transcriptional level
through transcription factors that bind to enhancers or silencers. Liver-specific transcription
factors activate genes required for hepatic function, while muscle-specific factors activate
myogenic genes. The DNA sequence of the gene is identical in all somatic cells (option A),
alternative splicing (option B) affects mRNA processing but not initial transcriptional activation,
and promoter mutations (option D) are not a normal regulatory mechanism.
Question 7: In a population of beetles, green coloration is dominant (G) and brown is
recessive (g). If 16% of the population exhibits the brown phenotype, what is the frequency
of the heterozygous genotype assuming Hardy-Weinberg equilibrium?
A. 0.16
B. 0.32
,C. 0.48
D. 0.64
CORRECT ANSWER: C. 0.48
Rationale: Under Hardy-Weinberg equilibrium, the frequency of the recessive phenotype (q²)
equals 0.16, so q = √0.16 = 0.4. Since p + q = 1, p = 0.6. The frequency of heterozygotes is 2pq =
2(0.6)(0.4) = 0.48. This calculation assumes no evolutionary forces are acting on the population.
Question 8: Which of the following best characterizes the fluid mosaic model of the plasma
membrane?
A. A rigid structure composed primarily of cellulose and lignin
B. A phospholipid bilayer with embedded proteins that can move laterally
C. A single layer of phospholipids with carbohydrates attached to the extracellular surface
D. A triple-layered structure with cholesterol forming the central core
CORRECT ANSWER: B. A phospholipid bilayer with embedded proteins that can move laterally
Rationale: The fluid mosaic model, proposed by Singer and Nicolson, describes the plasma
membrane as a dynamic phospholipid bilayer in which proteins are embedded and can diffuse
laterally. Fluidity is maintained by unsaturated fatty acids and cholesterol. Cellulose and lignin
are plant cell wall components (option A), membranes are bilayers not monolayers (option C),
and cholesterol modulates fluidity but does not form a central core (option D).
Question 9: During DNA replication, what is the primary function of DNA ligase?
A. Unwinding the double helix ahead of the replication fork
B. Synthesizing RNA primers to initiate DNA synthesis
C. Joining Okazaki fragments on the lagging strand by catalyzing phosphodiester bonds
D. Proofreading newly synthesized DNA and excising mismatched nucleotides
CORRECT ANSWER: C. Joining Okazaki fragments on the lagging strand by catalyzing
phosphodiester bonds
Rationale: DNA ligase seals nicks in the sugar-phosphate backbone by catalyzing the formation
of phosphodiester bonds between adjacent nucleotides. This is essential for joining Okazaki
fragments on the lagging strand. Helicase unwinds DNA (option A), primase synthesizes RNA
primers (option B), and DNA polymerase performs proofreading (option D).
Question 10: Which of the following processes directly requires ATP hydrolysis to transport
molecules against their concentration gradient?
A. Facilitated diffusion via channel proteins
B. Osmosis of water through aquaporins
C. Primary active transport via the sodium-potassium pump
D. Passive movement of oxygen across the lipid bilayer
CORRECT ANSWER: C. Primary active transport via the sodium-potassium pump
Rationale: Primary active transport directly uses ATP hydrolysis to pump ions against their
electrochemical gradient. The Na+/K+ ATPase hydrolyzes one ATP to export 3 Na+ and import 2
K+. Facilitated diffusion (option A), osmosis (option B), and simple diffusion of gases (option D)
are passive processes that do not require energy input.
Question 11: In photosynthesis, what is the primary role of the light-dependent reactions?
, A. To fix carbon dioxide into organic molecules using the Calvin cycle
B. To generate ATP and NADPH using light energy and water
C. To break down glucose into pyruvate in the stroma of chloroplasts
D. To release oxygen as a byproduct of carbohydrate synthesis
CORRECT ANSWER: B. To generate ATP and NADPH using light energy and water
Rationale: The light-dependent reactions occur in the thylakoid membranes and use light
energy to split water (releasing O₂), generate a proton gradient for ATP synthesis via
chemiosmosis, and reduce NADP+ to NADPH. These products (ATP and NADPH) are then used
in the Calvin cycle (option A) for carbon fixation. Glucose breakdown (option C) describes
glycolysis, not photosynthesis, and oxygen release (option D) is a consequence, not the primary
role.
Question 12: Which of the following best describes the relationship between genotype and
phenotype?
A. Genotype refers to observable traits, while phenotype refers to genetic makeup
B. Phenotype is determined solely by genotype, with no environmental influence
C. Genotype is the genetic constitution of an organism, while phenotype is the observable
expression of that genotype influenced by environment
D. Phenotype can be directly inherited, while genotype must be inferred from breeding
experiments
CORRECT ANSWER: C. Genotype is the genetic constitution of an organism, while phenotype
is the observable expression of that genotype influenced by environment
Rationale: Genotype represents the specific alleles an organism carries, while phenotype
encompasses observable characteristics resulting from genotype-environment interactions.
Option A reverses the definitions. Option B is incorrect because environment can modify
phenotype (e.g., nutrition affecting height). Option D is false because genotype is inherited
directly via gametes.
Question 13: What is the primary selective advantage of sexual reproduction over asexual
reproduction?
A. It requires less energy and time to produce offspring
B. It generates greater genetic diversity among offspring, enhancing adaptability
C. It ensures that all offspring are genetically identical to the parent
D. It allows for faster population growth in stable environments
CORRECT ANSWER: B. It generates greater genetic diversity among offspring, enhancing
adaptability
Rationale: Sexual reproduction combines genetic material from two parents through meiosis
and fertilization, creating novel allele combinations. This genetic variation provides raw
material for natural selection, improving population resilience to changing environments.
Asexual reproduction (options A, C, D) is more efficient but produces clones, limiting adaptive
potential.
Question 14: Which of the following molecules is NOT a component of the eukaryotic cell's
cytoskeleton?
