Page 1 of 105
GMS 5057 - Medical Cell Biology - Test 1 COMPLETE
QUESTIONS AND DETAILED SOLUTIONS LATEST UPDATE
THIS YEAR-JUST RELEASED
EXAM COVERAGE (Point Form)
• Cell Membrane Structure & Function: Fluid mosaic model, phospholipid bilayer, membrane
proteins (integral, peripheral, lipid-anchored), cholesterol, lipid rafts, membrane fluidity,
asymmetry
• Membrane Transport: Passive diffusion, facilitated diffusion (carriers, channels), active
transport (primary, secondary), Na+/K+ ATPase, ion channels, transporters (GLUT, SGLT),
aquaporins, endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis, transcytosis
• Organelles & Compartments: Nucleus (nuclear envelope, nuclear pore complex, lamins),
endoplasmic reticulum (rough, smooth, functions, protein synthesis, calcium storage,
detoxification), Golgi apparatus (cisternal maturation, glycosylation, sorting), lysosomes (acid
hydrolases, mannose-6-phosphate targeting, autophagy), peroxisomes (beta-oxidation, catalase,
biogenesis disorders), mitochondria (ATP synthesis, structure, import, apoptosis)
• Cytoskeleton: Microfilaments (actin, polymerization, treadmilling, cell motility, contractile ring),
intermediate filaments (keratin, vimentin, lamin, desmin, structure, functions), microtubules
(tubulin, polymerization, dynamic instability, MTOC, centrosome, functions, motor proteins
(kinesin, dynein), cilia, flagella)
• Cell Signaling: Signal transduction pathways (G protein-coupled receptors, receptor tyrosine
kinases, ion channel receptors, intracellular receptors), second messengers (cAMP, IP3, DAG,
Ca²⁺), MAPK pathway, PI3K/Akt pathway, JAK-STAT pathway, feedback regulation
• Cell Cycle & Division: Phases (G1, S, G2, M), checkpoints (G1/S, G2/M, spindle assembly),
cyclins, CDKs, CDK inhibitors, mitosis (prophase, metaphase, anaphase, telophase), cytokinesis,
regulation of cell cycle, apoptosis (intrinsic/extrinsic pathways, caspases, Bcl-2 family,
cytochrome c)
• Extracellular Matrix & Cell Adhesion: Collagen, elastin, proteoglycans, hyaluronan, fibronectin,
laminin, integrins, cadherins, selectins, IgSF CAMs, focal adhesions, desmosomes, adherens
junctions, tight junctions, gap junctions, hemidesmosomes
• Laboratory & Research Methods: Microscopy (light, fluorescence, confocal, electron), cell
fractionation, immunocytochemistry, Western blotting, PCR, gene knockdown (siRNA, shRNA,
CRISPR/Cas9)
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1. The fluid mosaic model of the cell membrane describes:
A) A static, rigid layer of phospholipids with proteins on the surface
B) A dynamic bilayer of phospholipids with proteins embedded that can move laterally
C) A trilaminar structure with cholesterol only
D) A solid layer of proteins with lipid pores
Answer: B) A dynamic bilayer of phospholipids with proteins embedded that can move laterally
Rationale: The fluid mosaic model, proposed by Singer and Nicolson, describes the membrane as a fluid
lipid bilayer with embedded proteins that can diffuse laterally. This allows flexibility and dynamic
function.
2. Which of the following membrane lipids is most abundant in the plasma membrane?
A) Cholesterol
B) Glycolipids
C) Phosphoglycerides (phospholipids)
D) Sphingolipids
Answer: C) Phosphoglycerides (phospholipids)
Rationale: Phosphoglycerides (e.g., phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine)
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are the most abundant phospholipids in the plasma membrane. Cholesterol is also abundant but not the
majority.
3. Which of the following is an example of a peripheral membrane protein?
A) An ion channel spanning the bilayer
B) A protein attached to the membrane via electrostatic interactions with lipid heads
C) A G protein-coupled receptor
D) An integrin with a transmembrane domain
Answer: B) A protein attached to the membrane via electrostatic interactions with lipid heads
Rationale: Peripheral membrane proteins are attached to the membrane surface by electrostatic
interactions or hydrogen bonding with lipid heads or other proteins. They can be removed by changes in
pH or ionic strength.
4. The asymmetric distribution of phospholipids in the plasma membrane is maintained by:
A) Spontaneous flipping of lipids
B) Flippases, floppases, and scramblases
C) Integral membrane proteins only
D) Cholesterol concentration
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Answer: B) Flippases, floppases, and scramblases
Rationale: Aminophospholipid translocases (flippases) move phosphatidylserine and
phosphatidylethanolamine to the inner leaflet; floppases move lipids outward; scramblases randomize
lipids during apoptosis. This maintains asymmetry.
5. Which of the following increases membrane fluidity?
A) Increased cholesterol content at high temperatures
B) Increased saturated fatty acid content
C) Increased unsaturated fatty acid content
D) Decreased temperature
Answer: C) Increased unsaturated fatty acid content
Rationale: Unsaturated fatty acids contain double bonds that create kinks, preventing tight packing of
lipids and increasing fluidity. Saturated fatty acids pack tightly, decreasing fluidity.
6. Cholesterol’s role in the plasma membrane at physiological temperatures is to:
A) Decrease fluidity exclusively
B) Increase fluidity exclusively
C) Buffer membrane fluidity (decrease fluidity at high temperature, increase fluidity at low temperature)
GMS 5057 - Medical Cell Biology - Test 1 COMPLETE
QUESTIONS AND DETAILED SOLUTIONS LATEST UPDATE
THIS YEAR-JUST RELEASED
EXAM COVERAGE (Point Form)
• Cell Membrane Structure & Function: Fluid mosaic model, phospholipid bilayer, membrane
proteins (integral, peripheral, lipid-anchored), cholesterol, lipid rafts, membrane fluidity,
asymmetry
• Membrane Transport: Passive diffusion, facilitated diffusion (carriers, channels), active
transport (primary, secondary), Na+/K+ ATPase, ion channels, transporters (GLUT, SGLT),
aquaporins, endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis, transcytosis
• Organelles & Compartments: Nucleus (nuclear envelope, nuclear pore complex, lamins),
endoplasmic reticulum (rough, smooth, functions, protein synthesis, calcium storage,
detoxification), Golgi apparatus (cisternal maturation, glycosylation, sorting), lysosomes (acid
hydrolases, mannose-6-phosphate targeting, autophagy), peroxisomes (beta-oxidation, catalase,
biogenesis disorders), mitochondria (ATP synthesis, structure, import, apoptosis)
• Cytoskeleton: Microfilaments (actin, polymerization, treadmilling, cell motility, contractile ring),
intermediate filaments (keratin, vimentin, lamin, desmin, structure, functions), microtubules
(tubulin, polymerization, dynamic instability, MTOC, centrosome, functions, motor proteins
(kinesin, dynein), cilia, flagella)
• Cell Signaling: Signal transduction pathways (G protein-coupled receptors, receptor tyrosine
kinases, ion channel receptors, intracellular receptors), second messengers (cAMP, IP3, DAG,
Ca²⁺), MAPK pathway, PI3K/Akt pathway, JAK-STAT pathway, feedback regulation
• Cell Cycle & Division: Phases (G1, S, G2, M), checkpoints (G1/S, G2/M, spindle assembly),
cyclins, CDKs, CDK inhibitors, mitosis (prophase, metaphase, anaphase, telophase), cytokinesis,
regulation of cell cycle, apoptosis (intrinsic/extrinsic pathways, caspases, Bcl-2 family,
cytochrome c)
• Extracellular Matrix & Cell Adhesion: Collagen, elastin, proteoglycans, hyaluronan, fibronectin,
laminin, integrins, cadherins, selectins, IgSF CAMs, focal adhesions, desmosomes, adherens
junctions, tight junctions, gap junctions, hemidesmosomes
• Laboratory & Research Methods: Microscopy (light, fluorescence, confocal, electron), cell
fractionation, immunocytochemistry, Western blotting, PCR, gene knockdown (siRNA, shRNA,
CRISPR/Cas9)
, Page 2 of 105
1. The fluid mosaic model of the cell membrane describes:
A) A static, rigid layer of phospholipids with proteins on the surface
B) A dynamic bilayer of phospholipids with proteins embedded that can move laterally
C) A trilaminar structure with cholesterol only
D) A solid layer of proteins with lipid pores
Answer: B) A dynamic bilayer of phospholipids with proteins embedded that can move laterally
Rationale: The fluid mosaic model, proposed by Singer and Nicolson, describes the membrane as a fluid
lipid bilayer with embedded proteins that can diffuse laterally. This allows flexibility and dynamic
function.
2. Which of the following membrane lipids is most abundant in the plasma membrane?
A) Cholesterol
B) Glycolipids
C) Phosphoglycerides (phospholipids)
D) Sphingolipids
Answer: C) Phosphoglycerides (phospholipids)
Rationale: Phosphoglycerides (e.g., phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine)
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are the most abundant phospholipids in the plasma membrane. Cholesterol is also abundant but not the
majority.
3. Which of the following is an example of a peripheral membrane protein?
A) An ion channel spanning the bilayer
B) A protein attached to the membrane via electrostatic interactions with lipid heads
C) A G protein-coupled receptor
D) An integrin with a transmembrane domain
Answer: B) A protein attached to the membrane via electrostatic interactions with lipid heads
Rationale: Peripheral membrane proteins are attached to the membrane surface by electrostatic
interactions or hydrogen bonding with lipid heads or other proteins. They can be removed by changes in
pH or ionic strength.
4. The asymmetric distribution of phospholipids in the plasma membrane is maintained by:
A) Spontaneous flipping of lipids
B) Flippases, floppases, and scramblases
C) Integral membrane proteins only
D) Cholesterol concentration
, Page 4 of 105
Answer: B) Flippases, floppases, and scramblases
Rationale: Aminophospholipid translocases (flippases) move phosphatidylserine and
phosphatidylethanolamine to the inner leaflet; floppases move lipids outward; scramblases randomize
lipids during apoptosis. This maintains asymmetry.
5. Which of the following increases membrane fluidity?
A) Increased cholesterol content at high temperatures
B) Increased saturated fatty acid content
C) Increased unsaturated fatty acid content
D) Decreased temperature
Answer: C) Increased unsaturated fatty acid content
Rationale: Unsaturated fatty acids contain double bonds that create kinks, preventing tight packing of
lipids and increasing fluidity. Saturated fatty acids pack tightly, decreasing fluidity.
6. Cholesterol’s role in the plasma membrane at physiological temperatures is to:
A) Decrease fluidity exclusively
B) Increase fluidity exclusively
C) Buffer membrane fluidity (decrease fluidity at high temperature, increase fluidity at low temperature)
