BIOL 180 UNIT TEST 2 | CELL STRUCTURE AND FUNCTION | ALL
QUESTIONS AND ANSWERS 2026/2027 | VERIFIED ANSWERS
PLUS RATIONALES | GRADED Q&A COMPREHENSIVE STUDY
GUIDE | VERIFIED LATEST 2027
1. Which foundational property of life is directly mediated by the plasma membrane's
selective permeability?
A. Sexual reproduction
B. Homeostasis
C. Genomic mutation
D. Thermal radiation
Rationale: Selective permeability allows the cell to strictly regulate its internal chemical
environment, maintaining homeostatic stability regardless of external fluctuations.
2. A technician prepares a tissue sample for light microscopy. Which cell organelle will be
clearly visible under a standard brightfield light microscope without fluorescent staining?
A. Ribosome
B. Nucleus
C. Peroxisome
D. Microfilament
Rationale: The nucleus is large enough (typically 5–10 micrometers) to be easily resolved
using standard brightfield light microscopy, unlike smaller subcellular structures like
ribosomes or microfilaments.
3. In a eukaryotic cell, where are the ribosomal RNA (rRNA) subunits assembled prior to
transport into the cytoplasm?
A. Smooth Endoplasmic Reticulum
B. Golgi apparatus
C. Nucleolus
,D. Lysosome
Rationale: The nucleolus is a dense specialized sub-region within the nucleus dedicated
specifically to rRNA transcription and ribosomal subunit assembly.
4. A cell biologist isolates an organelle that exhibits a double membrane, inner folds known
as cristae, and its own autonomous genome. What is this organelle?
A. Peroxisome
B. Mitochondrion
C. Central vacuole
D. Endosome
Rationale: Mitochondria are enclosed by two membranes, possess folded inner membranes
(cristae) to expand surface area for ATP synthesis, and maintain their own circular
mitochondrial DNA.
5. Which molecule forms the primary fluid matrix of the plasma membrane, presenting a
hydrophobic interior and hydrophilic exterior?
A. Triacylglycerol
B. Phospholipid
C. Glycogen
D. Cholesterol ester
Rationale: Phospholipids are amphipathic molecules that spontaneously self-assemble into a
bilayer in aqueous solutions, providing the fundamental structural framework of cell
membranes.
6. An investigator treats an animal cell culture with a metabolic inhibitor that selectively
depletes cellular ATP. Which transport process will be immediately halted?
A. Simple diffusion of oxygen
B. Osmotic water movement through aquaporins
C. Primary active transport via the $Na^+/K^+$ pump
,D. Facilitated diffusion of glucose through GLUT transporters
Rationale: Primary active transport mechanisms, such as the $Na^+/K^+$ ATPase pump,
directly consume ATP to pump ions against their electrochemical concentration gradients.
7. Plant cell walls are primarily composed of which complex carbohydrate polymer?
A. Chitin
B. Peptidoglycan
C. Cellulose
D. Starch
Rationale: Cellulose is an unbranched polymer of beta-1,4-linked glucose units that forms
rigid microfibrils, conferring structural strength and rigidity to plant cell walls.
8. Which organelle serves as the principal site for lipid synthesis, steroid hormone
production, and xenobiotic detoxification in mammalian hepatocytes?
A. Rough Endoplasmic Reticulum
B. Smooth Endoplasmic Reticulum
C. Lysosome
D. Centrosome
Rationale: The Smooth Endoplasmic Reticulum lacks attached ribosomes and specializes in
lipid and steroid biosynthesis, calcium storage, and enzymatic detoxification of drugs and
toxins.
9. What is the primary function of lysosomes in animal cells during normal cellular
maintenance?
A. Protein translation from mRNA transcripts
B. Degradation of damaged organelles and foreign particles via acid hydrolases
C. Generation of electrochemical gradients for oxidative phosphorylation
D. Synthesis of extracellular matrix fibers like collagen
, Rationale: Lysosomes contain acidic hydrolytic enzymes that fuse with autophagosomes or
endosomes to break down metabolic waste, worn-out organelles, and internalized
pathogens.
10. When plant cells are placed in an extremely hypertonic salt solution, water leaves the
vacuole, causing the plasma membrane to shrink away from the rigid cell wall. What is this
physiological phenomenon termed?
A. Hemolysis
B. Plasmolysis
C. Cytolysis
D. Crenation
Rationale: Plasmolysis is the shrinking of a plant cell's protoplast away from its surrounding
cell wall due to water loss driven by osmosis in a hypertonic environment.
11. Which membrane junction prevents the paracellular leakage of fluids and digestive
solutes between adjacent epithelial cells in the human intestinal mucosa?
A. Desmosome
B. Tight junction
C. Gap junction
D. Plasmodesmata
Rationale: Tight junctions (occludin and claudin networks) form continuous fluid-tight seals
around the apical borders of epithelial cells to prevent unregulated paracellular movement.
12. A mammalian cell line displays a genetic mutation resulting in non-functional signal
recognition particle (SRP) receptors on the Endoplasmic Reticulum. What cellular defect
will occur?
A. Nuclear DNA replication will cease entirely.
B. Ribosomes translating secretory proteins will fail to dock onto the Rough ER membrane.
C. Mitochondria will lose the ability to perform the citric acid cycle.
D. Peroxisomes will accumulate excess hydrogen peroxide.
QUESTIONS AND ANSWERS 2026/2027 | VERIFIED ANSWERS
PLUS RATIONALES | GRADED Q&A COMPREHENSIVE STUDY
GUIDE | VERIFIED LATEST 2027
1. Which foundational property of life is directly mediated by the plasma membrane's
selective permeability?
A. Sexual reproduction
B. Homeostasis
C. Genomic mutation
D. Thermal radiation
Rationale: Selective permeability allows the cell to strictly regulate its internal chemical
environment, maintaining homeostatic stability regardless of external fluctuations.
2. A technician prepares a tissue sample for light microscopy. Which cell organelle will be
clearly visible under a standard brightfield light microscope without fluorescent staining?
A. Ribosome
B. Nucleus
C. Peroxisome
D. Microfilament
Rationale: The nucleus is large enough (typically 5–10 micrometers) to be easily resolved
using standard brightfield light microscopy, unlike smaller subcellular structures like
ribosomes or microfilaments.
3. In a eukaryotic cell, where are the ribosomal RNA (rRNA) subunits assembled prior to
transport into the cytoplasm?
A. Smooth Endoplasmic Reticulum
B. Golgi apparatus
C. Nucleolus
,D. Lysosome
Rationale: The nucleolus is a dense specialized sub-region within the nucleus dedicated
specifically to rRNA transcription and ribosomal subunit assembly.
4. A cell biologist isolates an organelle that exhibits a double membrane, inner folds known
as cristae, and its own autonomous genome. What is this organelle?
A. Peroxisome
B. Mitochondrion
C. Central vacuole
D. Endosome
Rationale: Mitochondria are enclosed by two membranes, possess folded inner membranes
(cristae) to expand surface area for ATP synthesis, and maintain their own circular
mitochondrial DNA.
5. Which molecule forms the primary fluid matrix of the plasma membrane, presenting a
hydrophobic interior and hydrophilic exterior?
A. Triacylglycerol
B. Phospholipid
C. Glycogen
D. Cholesterol ester
Rationale: Phospholipids are amphipathic molecules that spontaneously self-assemble into a
bilayer in aqueous solutions, providing the fundamental structural framework of cell
membranes.
6. An investigator treats an animal cell culture with a metabolic inhibitor that selectively
depletes cellular ATP. Which transport process will be immediately halted?
A. Simple diffusion of oxygen
B. Osmotic water movement through aquaporins
C. Primary active transport via the $Na^+/K^+$ pump
,D. Facilitated diffusion of glucose through GLUT transporters
Rationale: Primary active transport mechanisms, such as the $Na^+/K^+$ ATPase pump,
directly consume ATP to pump ions against their electrochemical concentration gradients.
7. Plant cell walls are primarily composed of which complex carbohydrate polymer?
A. Chitin
B. Peptidoglycan
C. Cellulose
D. Starch
Rationale: Cellulose is an unbranched polymer of beta-1,4-linked glucose units that forms
rigid microfibrils, conferring structural strength and rigidity to plant cell walls.
8. Which organelle serves as the principal site for lipid synthesis, steroid hormone
production, and xenobiotic detoxification in mammalian hepatocytes?
A. Rough Endoplasmic Reticulum
B. Smooth Endoplasmic Reticulum
C. Lysosome
D. Centrosome
Rationale: The Smooth Endoplasmic Reticulum lacks attached ribosomes and specializes in
lipid and steroid biosynthesis, calcium storage, and enzymatic detoxification of drugs and
toxins.
9. What is the primary function of lysosomes in animal cells during normal cellular
maintenance?
A. Protein translation from mRNA transcripts
B. Degradation of damaged organelles and foreign particles via acid hydrolases
C. Generation of electrochemical gradients for oxidative phosphorylation
D. Synthesis of extracellular matrix fibers like collagen
, Rationale: Lysosomes contain acidic hydrolytic enzymes that fuse with autophagosomes or
endosomes to break down metabolic waste, worn-out organelles, and internalized
pathogens.
10. When plant cells are placed in an extremely hypertonic salt solution, water leaves the
vacuole, causing the plasma membrane to shrink away from the rigid cell wall. What is this
physiological phenomenon termed?
A. Hemolysis
B. Plasmolysis
C. Cytolysis
D. Crenation
Rationale: Plasmolysis is the shrinking of a plant cell's protoplast away from its surrounding
cell wall due to water loss driven by osmosis in a hypertonic environment.
11. Which membrane junction prevents the paracellular leakage of fluids and digestive
solutes between adjacent epithelial cells in the human intestinal mucosa?
A. Desmosome
B. Tight junction
C. Gap junction
D. Plasmodesmata
Rationale: Tight junctions (occludin and claudin networks) form continuous fluid-tight seals
around the apical borders of epithelial cells to prevent unregulated paracellular movement.
12. A mammalian cell line displays a genetic mutation resulting in non-functional signal
recognition particle (SRP) receptors on the Endoplasmic Reticulum. What cellular defect
will occur?
A. Nuclear DNA replication will cease entirely.
B. Ribosomes translating secretory proteins will fail to dock onto the Rough ER membrane.
C. Mitochondria will lose the ability to perform the citric acid cycle.
D. Peroxisomes will accumulate excess hydrogen peroxide.
