MMSC491 Exam 2 - Comprehensive Practice
Examination WITH CORRECT ANSWERS WELL
VERIFIED WITH IN-DEPTH RATIONALES.
Section A: Cellular and Molecular Biology (Questions 1-30)
1. Which organelle is primarily responsible for ATP production through oxidative phosphorylation?
A) Golgi apparatus
B) Endoplasmic reticulum
C) Mitochondria
D) Lysosomes
ANSWER: C) Mitochondria
Rationale: Mitochondria are the powerhouses of the cell, containing the electron transport chain and
ATP synthase complexes necessary for oxidative phosphorylation. The inner mitochondrial membrane
houses the protein complexes that generate the proton gradient driving ATP synthesis.
2. What is the primary function of the smooth endoplasmic reticulum?
A) Protein synthesis
B) Lipid synthesis and detoxification
C) ATP production
D) Protein modification
ANSWER: B) Lipid synthesis and detoxification
Rationale: The smooth ER lacks ribosomes and is specialized for lipid synthesis, steroid hormone
production, and detoxification of drugs and poisons. The rough ER, by contrast, is involved in protein
synthesis and modification.
3. Which of the following is a characteristic of prokaryotic cells?
A) Membrane-bound nucleus
,B) Membrane-bound organelles
C) 70S ribosomes
D) Linear chromosomes
ANSWER: C) 70S ribosomes
Rationale: Prokaryotic cells contain 70S ribosomes (50S + 30S subunits), whereas eukaryotic cells contain
80S ribosomes (60S + 40S subunits). Prokaryotes lack membrane-bound organelles and have circular
chromosomes.
4. What is the role of the Golgi apparatus in protein trafficking?
A) Synthesizing proteins
B) Modifying, sorting, and packaging proteins
C) Degrading proteins
D) Transcribing DNA
ANSWER: B) Modifying, sorting, and packaging proteins
Rationale: The Golgi apparatus functions as the cell's post office, modifying proteins through
glycosylation, sorting them based on destination tags, and packaging them into vesicles for transport to
various cellular locations or secretion.
5. Which transport mechanism requires cellular energy?
A) Passive diffusion
B) Facilitated diffusion
C) Active transport
D) Osmosis
ANSWER: C) Active transport
Rationale: Active transport moves molecules against their concentration gradient, requiring ATP energy.
Passive diffusion, facilitated diffusion, and osmosis are passive processes that do not require energy
input.
,6. What is the function of lysosomes?
A) Protein synthesis
B) Cellular digestion and waste breakdown
C) Energy production
D) DNA replication
ANSWER: B) Cellular digestion and waste breakdown
Rationale: Lysosomes contain hydrolytic enzymes that break down macromolecules, old organelles, and
cellular debris. They function in autophagy and phagocytosis, maintaining cellular homeostasis through
degradation and recycling.
7. Which of the following describes the structure of the plasma membrane?
A) Solid lipid layer with embedded proteins
B) Phospholipid bilayer with embedded proteins
C) Monolayer of glycolipids
D) Protein layer with lipid inclusions
ANSWER: B) Phospholipid bilayer with embedded proteins
Rationale: The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with
amphipathic properties, containing integral and peripheral proteins that float within the membrane,
providing selective permeability and cellular functions.
8. What is the function of microvilli?
A) Cellular movement
B) Increasing surface area for absorption
C) Cell-to-cell communication
D) Genetic material storage
ANSWER: B) Increasing surface area for absorption
, Rationale: Microvilli are finger-like projections of the plasma membrane that increase the surface area
for absorption, particularly in epithelial cells of the small intestine and kidney tubules where nutrient
and ion absorption occurs.
9. Which cytoskeletal component is responsible for cellular movement?
A) Microtubules
B) Actin filaments
C) Intermediate filaments
D) All of the above
ANSWER: B) Actin filaments
Rationale: Actin filaments (microfilaments) are primarily responsible for cellular movement, including
cell crawling, contraction, and cytokinesis. Microtubules are involved in intracellular transport and
chromosome segregation, while intermediate filaments provide structural support.
10. What is the primary function of tight junctions?
A) Allow communication between cells
B) Prevent leakage between cells
C) Anchor cells to extracellular matrix
D) Allow movement of ions between cells
ANSWER: B) Prevent leakage between cells
Rationale: Tight junctions form a seal between adjacent cells, preventing the passage of molecules
through the paracellular space. They are essential for maintaining compartmentalization in epithelial
tissues, such as in the blood-brain barrier.
11. Where does transcription occur in eukaryotic cells?
A) Cytoplasm
B) Nucleus
C) Mitochondria
D) Ribosomes
Examination WITH CORRECT ANSWERS WELL
VERIFIED WITH IN-DEPTH RATIONALES.
Section A: Cellular and Molecular Biology (Questions 1-30)
1. Which organelle is primarily responsible for ATP production through oxidative phosphorylation?
A) Golgi apparatus
B) Endoplasmic reticulum
C) Mitochondria
D) Lysosomes
ANSWER: C) Mitochondria
Rationale: Mitochondria are the powerhouses of the cell, containing the electron transport chain and
ATP synthase complexes necessary for oxidative phosphorylation. The inner mitochondrial membrane
houses the protein complexes that generate the proton gradient driving ATP synthesis.
2. What is the primary function of the smooth endoplasmic reticulum?
A) Protein synthesis
B) Lipid synthesis and detoxification
C) ATP production
D) Protein modification
ANSWER: B) Lipid synthesis and detoxification
Rationale: The smooth ER lacks ribosomes and is specialized for lipid synthesis, steroid hormone
production, and detoxification of drugs and poisons. The rough ER, by contrast, is involved in protein
synthesis and modification.
3. Which of the following is a characteristic of prokaryotic cells?
A) Membrane-bound nucleus
,B) Membrane-bound organelles
C) 70S ribosomes
D) Linear chromosomes
ANSWER: C) 70S ribosomes
Rationale: Prokaryotic cells contain 70S ribosomes (50S + 30S subunits), whereas eukaryotic cells contain
80S ribosomes (60S + 40S subunits). Prokaryotes lack membrane-bound organelles and have circular
chromosomes.
4. What is the role of the Golgi apparatus in protein trafficking?
A) Synthesizing proteins
B) Modifying, sorting, and packaging proteins
C) Degrading proteins
D) Transcribing DNA
ANSWER: B) Modifying, sorting, and packaging proteins
Rationale: The Golgi apparatus functions as the cell's post office, modifying proteins through
glycosylation, sorting them based on destination tags, and packaging them into vesicles for transport to
various cellular locations or secretion.
5. Which transport mechanism requires cellular energy?
A) Passive diffusion
B) Facilitated diffusion
C) Active transport
D) Osmosis
ANSWER: C) Active transport
Rationale: Active transport moves molecules against their concentration gradient, requiring ATP energy.
Passive diffusion, facilitated diffusion, and osmosis are passive processes that do not require energy
input.
,6. What is the function of lysosomes?
A) Protein synthesis
B) Cellular digestion and waste breakdown
C) Energy production
D) DNA replication
ANSWER: B) Cellular digestion and waste breakdown
Rationale: Lysosomes contain hydrolytic enzymes that break down macromolecules, old organelles, and
cellular debris. They function in autophagy and phagocytosis, maintaining cellular homeostasis through
degradation and recycling.
7. Which of the following describes the structure of the plasma membrane?
A) Solid lipid layer with embedded proteins
B) Phospholipid bilayer with embedded proteins
C) Monolayer of glycolipids
D) Protein layer with lipid inclusions
ANSWER: B) Phospholipid bilayer with embedded proteins
Rationale: The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with
amphipathic properties, containing integral and peripheral proteins that float within the membrane,
providing selective permeability and cellular functions.
8. What is the function of microvilli?
A) Cellular movement
B) Increasing surface area for absorption
C) Cell-to-cell communication
D) Genetic material storage
ANSWER: B) Increasing surface area for absorption
, Rationale: Microvilli are finger-like projections of the plasma membrane that increase the surface area
for absorption, particularly in epithelial cells of the small intestine and kidney tubules where nutrient
and ion absorption occurs.
9. Which cytoskeletal component is responsible for cellular movement?
A) Microtubules
B) Actin filaments
C) Intermediate filaments
D) All of the above
ANSWER: B) Actin filaments
Rationale: Actin filaments (microfilaments) are primarily responsible for cellular movement, including
cell crawling, contraction, and cytokinesis. Microtubules are involved in intracellular transport and
chromosome segregation, while intermediate filaments provide structural support.
10. What is the primary function of tight junctions?
A) Allow communication between cells
B) Prevent leakage between cells
C) Anchor cells to extracellular matrix
D) Allow movement of ions between cells
ANSWER: B) Prevent leakage between cells
Rationale: Tight junctions form a seal between adjacent cells, preventing the passage of molecules
through the paracellular space. They are essential for maintaining compartmentalization in epithelial
tissues, such as in the blood-brain barrier.
11. Where does transcription occur in eukaryotic cells?
A) Cytoplasm
B) Nucleus
C) Mitochondria
D) Ribosomes
