SEMMELWEIS UNIVERSITY ENTRANCE EXAM
Medicine — Biology 2026 | 200 Advanced Practice Questions
SECTION 1: CELL BIOLOGY & CELL STRUCTURE
1. The fluid mosaic model of the plasma membrane, proposed by Singer and Nicolson in 1972,
describes the membrane as:
A) A rigid bilayer of phospholipids with proteins permanently embedded at fixed
positions
B) A dynamic structure where phospholipids and proteins can move laterally within the
bilayer, with proteins "floating" in a fluid lipid sea (correct answer)
C) A single layer of amphipathic molecules with proteins attached exclusively to the
outer surface
D) A crystalline structure that becomes fluid only at temperatures above 37°C
Rationale: The fluid mosaic model emphasizes two key properties: fluidity (lateral movement of
lipids and proteins) and mosaic organization (proteins of various types embedded throughout the
bilayer). Membrane fluidity is regulated by cholesterol content and fatty acid saturation.
2. Which of the following correctly describes the asymmetry of the plasma membrane?
A) The inner leaflet contains primarily phosphatidylcholine and sphingomyelin
B) Phosphatidylserine and phosphatidylethanolamine are preferentially located in the
cytoplasmic (inner) leaflet, while sphingomyelin and phosphatidylcholine predominate in
the outer leaflet (correct answer)
C) Cholesterol is found exclusively in the outer leaflet
D) Glycolipids are distributed equally between both leaflets of the membrane
Rationale: Membrane asymmetry is functionally critical. Phosphatidylserine on the inner leaflet
serves as a docking site for signaling proteins and is externalized during apoptosis (an "eat me"
signal). Glycolipids are exclusively on the outer leaflet contributing to the glycocalyx.
3. The "signal hypothesis" proposed by Blobel and Sabatini describes:
A) How mitochondrial proteins are imported from the cytoplasm
, B) The mechanism by which proteins destined for the secretory pathway are directed to
the rough ER by a hydrophobic N-terminal signal sequence recognized by the Signal
Recognition Particle (SRP) (correct answer)
C) The process by which nuclear proteins are imported through nuclear pores
D) How lysosomal enzymes are marked with mannose-6-phosphate for targeting
Rationale: The signal hypothesis (for which Blobel received the Nobel Prize in 1999) explains
co-translational insertion of secretory and membrane proteins into the ER. The SRP binds the
signal sequence and the ribosome, pausing translation until the complex docks at the SRP
receptor on the ER membrane.
4. Mitochondria possess their own ribosomes (mitoribosomes), which are:
A) Identical to cytoplasmic 80S ribosomes since mitochondria are derived from
eukaryotic cells
B) Smaller than cytoplasmic ribosomes (55S in mammals) and more similar to bacterial
70S ribosomes, consistent with the endosymbiotic origin of mitochondria (correct
answer)
C) 70S ribosomes identical to those found in chloroplasts and bacteria
D) Found only in the mitochondrial intermembrane space
Rationale: Mammalian mitoribosomes are 55S (28S large subunit + 39S small subunit) —
distinct from both cytoplasmic 80S and prokaryotic 70S ribosomes. Their similarity to bacterial
ribosomes (sensitivity to antibiotics like chloramphenicol) supports the endosymbiotic theory.
5. The "motor protein" kinesin differs from dynein in that kinesin:
A) Moves cargo toward the minus end (MTOC) of microtubules, while dynein moves
toward the plus end
B) Primarily moves cargo toward the plus end (periphery) of microtubules, while
cytoplasmic dynein moves toward the minus end (MTOC) (correct answer)
C) Uses actin filaments as its track rather than microtubules
D) Is a minus-end directed motor that requires ATP hydrolysis only at the centrosome
Rationale: Kinesin (anterograde transport) moves cargo from the cell center to the periphery
(toward microtubule plus ends). Dynein (retrograde transport) moves cargo toward the minus
ends at the MTOC. This bidirectional transport system is essential for neuronal axonal transport
and organelle positioning.
6. During "receptor-mediated endocytosis," the LDL receptor:
, A) Remains constitutively in clathrin-coated pits regardless of ligand binding
B) Concentrates in clathrin-coated pits through interactions between the receptor's
cytoplasmic tail and adaptor proteins, internalizes LDL, then recycles back to the plasma
membrane while LDL is delivered to lysosomes (correct answer)
C) Is degraded in lysosomes along with the LDL particle after each round of endocytosis
D) Requires LDL binding before clustering into clathrin-coated pits
Rationale: The LDL receptor is the classic receptor-mediated endocytosis example. The receptor
recycles (recycling endosome → plasma membrane) approximately 200 times in its lifetime.
Mutations causing failure of receptor clustering (not just LDL binding) cause familial
hypercholesterolemia.
7. The "unfolded protein response" (UPR) is activated when:
A) Ribosomes detach from the rough ER during periods of low translation
B) Misfolded proteins accumulate in the ER lumen, causing ER stress — the UPR
attempts to restore proteostasis through three parallel signaling branches (IRE1, PERK,
ATF6) (correct answer)
C) The Golgi apparatus becomes saturated with glycoproteins awaiting modification
D) Lysosomal enzymes are misdirected to the secretory pathway
Rationale: UPR is activated when ER chaperone capacity is overwhelmed. The three UPR
branches: IRE1 (splices XBP1 mRNA), PERK (phosphorylates eIF2α to reduce translation), and
ATF6 (activates ER biogenesis genes). Chronic ER stress can trigger apoptosis.
8. "Lipid rafts" in the plasma membrane are characterized by:
A) High phosphatidylinositol content and association with cytoskeletal proteins
B) Enrichment in cholesterol and sphingolipids, forming ordered (Lo) phase
microdomains that concentrate GPI-anchored proteins and certain signaling molecules
(correct answer)
C) Exclusive location in the inner leaflet of the plasma membrane
D) Fluid, disordered regions that serve as sites of membrane protein degradation
Rationale: Lipid rafts are detergent-resistant membrane microdomains enriched in cholesterol
and sphingolipids. They serve as platforms for signal transduction, membrane trafficking, and
pathogen entry. GPI-anchored proteins preferentially partition into rafts.
9. The "nuclear lamina" in eukaryotic cells:
, A) Is composed of actin and myosin filaments that provide nuclear structural support
B) Is a meshwork of intermediate filaments (lamins A, B, C) lining the inner nuclear
membrane, providing structural support, organizing chromatin, and serving as anchor
points for nuclear pore complexes (correct answer)
C) Is found exclusively in post-mitotic cells since it must dissolve during cell division
D) Regulates only mRNA export from the nucleus without structural function
Rationale: The nuclear lamina (type V intermediate filaments) provides structural integrity to
the nucleus and plays roles in DNA replication, gene expression, and cell differentiation.
Mutations in lamin A cause a family of diseases called laminopathies, including Hutchinson-
Gilford progeria syndrome.
10. Which correctly describes "gap junctions" compared to "tight junctions"?
A) Gap junctions create a seal preventing paracellular transport; tight junctions allow
direct cell-to-cell communication
B) Gap junctions are channels (connexons) allowing direct cytoplasmic continuity
between adjacent cells for ions and small molecules; tight junctions (occludin/claudin-
based) seal the paracellular space preventing molecular passage (correct answer)
C) Both junction types are formed by the same protein family — claudins
D) Gap junctions are found exclusively in cardiac muscle; tight junctions are found only
in epithelial cells
Rationale: Gap junctions (connexins forming hexameric connexons) allow passage of ions,
second messengers, and metabolites up to ~1kDa between cells — critical for cardiac
conduction, smooth muscle coordination, and embryonic development. Tight junctions create a
paracellular barrier fundamental to epithelial function.
SECTION 2: GENETICS & MOLECULAR BIOLOGY
11. The "central dogma" of molecular biology as stated by Crick in 1958 and revised in 1970, in
its complete form, includes:
A) DNA → RNA → Protein as the only possible information flow
B) DNA can be replicated (DNA → DNA), transcribed (DNA → RNA), and translated
(RNA → Protein); reverse transcription (RNA → DNA) is possible; but protein sequence
information cannot flow back to nucleic acids (correct answer)
C) RNA can be directly converted to protein without DNA involvement in all organisms
D) Protein → DNA conversion occurs in retroviruses during their replication cycle
Rationale: The 1970 revision of the central dogma added RNA → DNA (reverse transcriptase,
discovered by Baltimore and Temin) and RNA → RNA (RNA replication). The absolute
Medicine — Biology 2026 | 200 Advanced Practice Questions
SECTION 1: CELL BIOLOGY & CELL STRUCTURE
1. The fluid mosaic model of the plasma membrane, proposed by Singer and Nicolson in 1972,
describes the membrane as:
A) A rigid bilayer of phospholipids with proteins permanently embedded at fixed
positions
B) A dynamic structure where phospholipids and proteins can move laterally within the
bilayer, with proteins "floating" in a fluid lipid sea (correct answer)
C) A single layer of amphipathic molecules with proteins attached exclusively to the
outer surface
D) A crystalline structure that becomes fluid only at temperatures above 37°C
Rationale: The fluid mosaic model emphasizes two key properties: fluidity (lateral movement of
lipids and proteins) and mosaic organization (proteins of various types embedded throughout the
bilayer). Membrane fluidity is regulated by cholesterol content and fatty acid saturation.
2. Which of the following correctly describes the asymmetry of the plasma membrane?
A) The inner leaflet contains primarily phosphatidylcholine and sphingomyelin
B) Phosphatidylserine and phosphatidylethanolamine are preferentially located in the
cytoplasmic (inner) leaflet, while sphingomyelin and phosphatidylcholine predominate in
the outer leaflet (correct answer)
C) Cholesterol is found exclusively in the outer leaflet
D) Glycolipids are distributed equally between both leaflets of the membrane
Rationale: Membrane asymmetry is functionally critical. Phosphatidylserine on the inner leaflet
serves as a docking site for signaling proteins and is externalized during apoptosis (an "eat me"
signal). Glycolipids are exclusively on the outer leaflet contributing to the glycocalyx.
3. The "signal hypothesis" proposed by Blobel and Sabatini describes:
A) How mitochondrial proteins are imported from the cytoplasm
, B) The mechanism by which proteins destined for the secretory pathway are directed to
the rough ER by a hydrophobic N-terminal signal sequence recognized by the Signal
Recognition Particle (SRP) (correct answer)
C) The process by which nuclear proteins are imported through nuclear pores
D) How lysosomal enzymes are marked with mannose-6-phosphate for targeting
Rationale: The signal hypothesis (for which Blobel received the Nobel Prize in 1999) explains
co-translational insertion of secretory and membrane proteins into the ER. The SRP binds the
signal sequence and the ribosome, pausing translation until the complex docks at the SRP
receptor on the ER membrane.
4. Mitochondria possess their own ribosomes (mitoribosomes), which are:
A) Identical to cytoplasmic 80S ribosomes since mitochondria are derived from
eukaryotic cells
B) Smaller than cytoplasmic ribosomes (55S in mammals) and more similar to bacterial
70S ribosomes, consistent with the endosymbiotic origin of mitochondria (correct
answer)
C) 70S ribosomes identical to those found in chloroplasts and bacteria
D) Found only in the mitochondrial intermembrane space
Rationale: Mammalian mitoribosomes are 55S (28S large subunit + 39S small subunit) —
distinct from both cytoplasmic 80S and prokaryotic 70S ribosomes. Their similarity to bacterial
ribosomes (sensitivity to antibiotics like chloramphenicol) supports the endosymbiotic theory.
5. The "motor protein" kinesin differs from dynein in that kinesin:
A) Moves cargo toward the minus end (MTOC) of microtubules, while dynein moves
toward the plus end
B) Primarily moves cargo toward the plus end (periphery) of microtubules, while
cytoplasmic dynein moves toward the minus end (MTOC) (correct answer)
C) Uses actin filaments as its track rather than microtubules
D) Is a minus-end directed motor that requires ATP hydrolysis only at the centrosome
Rationale: Kinesin (anterograde transport) moves cargo from the cell center to the periphery
(toward microtubule plus ends). Dynein (retrograde transport) moves cargo toward the minus
ends at the MTOC. This bidirectional transport system is essential for neuronal axonal transport
and organelle positioning.
6. During "receptor-mediated endocytosis," the LDL receptor:
, A) Remains constitutively in clathrin-coated pits regardless of ligand binding
B) Concentrates in clathrin-coated pits through interactions between the receptor's
cytoplasmic tail and adaptor proteins, internalizes LDL, then recycles back to the plasma
membrane while LDL is delivered to lysosomes (correct answer)
C) Is degraded in lysosomes along with the LDL particle after each round of endocytosis
D) Requires LDL binding before clustering into clathrin-coated pits
Rationale: The LDL receptor is the classic receptor-mediated endocytosis example. The receptor
recycles (recycling endosome → plasma membrane) approximately 200 times in its lifetime.
Mutations causing failure of receptor clustering (not just LDL binding) cause familial
hypercholesterolemia.
7. The "unfolded protein response" (UPR) is activated when:
A) Ribosomes detach from the rough ER during periods of low translation
B) Misfolded proteins accumulate in the ER lumen, causing ER stress — the UPR
attempts to restore proteostasis through three parallel signaling branches (IRE1, PERK,
ATF6) (correct answer)
C) The Golgi apparatus becomes saturated with glycoproteins awaiting modification
D) Lysosomal enzymes are misdirected to the secretory pathway
Rationale: UPR is activated when ER chaperone capacity is overwhelmed. The three UPR
branches: IRE1 (splices XBP1 mRNA), PERK (phosphorylates eIF2α to reduce translation), and
ATF6 (activates ER biogenesis genes). Chronic ER stress can trigger apoptosis.
8. "Lipid rafts" in the plasma membrane are characterized by:
A) High phosphatidylinositol content and association with cytoskeletal proteins
B) Enrichment in cholesterol and sphingolipids, forming ordered (Lo) phase
microdomains that concentrate GPI-anchored proteins and certain signaling molecules
(correct answer)
C) Exclusive location in the inner leaflet of the plasma membrane
D) Fluid, disordered regions that serve as sites of membrane protein degradation
Rationale: Lipid rafts are detergent-resistant membrane microdomains enriched in cholesterol
and sphingolipids. They serve as platforms for signal transduction, membrane trafficking, and
pathogen entry. GPI-anchored proteins preferentially partition into rafts.
9. The "nuclear lamina" in eukaryotic cells:
, A) Is composed of actin and myosin filaments that provide nuclear structural support
B) Is a meshwork of intermediate filaments (lamins A, B, C) lining the inner nuclear
membrane, providing structural support, organizing chromatin, and serving as anchor
points for nuclear pore complexes (correct answer)
C) Is found exclusively in post-mitotic cells since it must dissolve during cell division
D) Regulates only mRNA export from the nucleus without structural function
Rationale: The nuclear lamina (type V intermediate filaments) provides structural integrity to
the nucleus and plays roles in DNA replication, gene expression, and cell differentiation.
Mutations in lamin A cause a family of diseases called laminopathies, including Hutchinson-
Gilford progeria syndrome.
10. Which correctly describes "gap junctions" compared to "tight junctions"?
A) Gap junctions create a seal preventing paracellular transport; tight junctions allow
direct cell-to-cell communication
B) Gap junctions are channels (connexons) allowing direct cytoplasmic continuity
between adjacent cells for ions and small molecules; tight junctions (occludin/claudin-
based) seal the paracellular space preventing molecular passage (correct answer)
C) Both junction types are formed by the same protein family — claudins
D) Gap junctions are found exclusively in cardiac muscle; tight junctions are found only
in epithelial cells
Rationale: Gap junctions (connexins forming hexameric connexons) allow passage of ions,
second messengers, and metabolites up to ~1kDa between cells — critical for cardiac
conduction, smooth muscle coordination, and embryonic development. Tight junctions create a
paracellular barrier fundamental to epithelial function.
SECTION 2: GENETICS & MOLECULAR BIOLOGY
11. The "central dogma" of molecular biology as stated by Crick in 1958 and revised in 1970, in
its complete form, includes:
A) DNA → RNA → Protein as the only possible information flow
B) DNA can be replicated (DNA → DNA), transcribed (DNA → RNA), and translated
(RNA → Protein); reverse transcription (RNA → DNA) is possible; but protein sequence
information cannot flow back to nucleic acids (correct answer)
C) RNA can be directly converted to protein without DNA involvement in all organisms
D) Protein → DNA conversion occurs in retroviruses during their replication cycle
Rationale: The 1970 revision of the central dogma added RNA → DNA (reverse transcriptase,
discovered by Baltimore and Temin) and RNA → RNA (RNA replication). The absolute
