Albania Medicine Entrance Exam — Provimi i Informatizuar i Mjekësisë

Which organelle contains acid hydrolases and serves as the primary site for intracellular digestion and autophagy in eukaryotic cells?

• ALysosome
• BPeroxisome
• CGolgi apparatus
• DEndoplasmic reticulum

In animal cells, what is the exact stoichiometric ion exchange and energy requirement of the plasma membrane Na+/K+ ATPase pump per catalytic cycle?

• A3 Na+ ions exported out, 2 K+ ions imported in, utilizing 1 ATP molecule
• B2 Na+ ions exported out, 3 K+ ions imported in, utilizing 1 ATP molecule
• C3 Na+ ions imported in, 2 K+ ions exported out, utilizing 1 ATP molecule
• D3 Na+ ions exported out, 3 K+ ions imported in, utilizing 2 ATP molecules

During which phase of mitosis do sister chromatids synchronously separate and move toward opposite poles of the mitotic spindle?

• AAnaphase
• BProphase
• CMetaphase
• DTelophase

What is the primary physiological function of cholesterol within the animal cell plasma membrane?

• AIt acts as a fluidity buffer, reducing membrane fluidity at high temperatures and hinderi…
• BIt acts as a primary active transport channel for polar hydrophilic cations across the li…
• CIt provides enzymatic catalytic activity for phospholipid and glycolipid degradation
• DIt forms the principal hydrophilic outer barrier that directly interfaces with the aqueou…

In aerobic cellular respiration, what is the ultimate terminal electron acceptor in the mitochondrial electron transport chain, and what product is formed upon its reduction?

• AMolecular oxygen (O2), which is reduced to water (H2O)
• BNAD+, which is reduced to NADH
• CPyruvate, which is reduced to lactate
• DCytochrome c, which is reduced to ubiquinol

Which eukaryotic organelle is primarily dedicated to the synthesis, folding, and post-translational modification of membrane-bound, lysosomal, and secretory proteins?

• ARough endoplasmic reticulum
• BSmooth endoplasmic reticulum
• CFree cytosolic ribosomes
• DPeroxisome

What morphological change occurs when human erythrocytes (red blood cells) are placed into a hypertonic sodium chloride solution (e.g., 3.0% NaCl)?

• ACrenation (cell shrinkage due to net osmotic water efflux)
• BHemolysis (cell swelling and bursting due to net osmotic water influx)
• CNo change in volume because erythrocytes actively pump water against concentration gradie…
• DImmediate division by binary fission due to osmotic shock

Which molecular event is required for a mammalian cell to pass the G1/S restriction checkpoint and commit to DNA replication?

• APhosphorylation of the retinoblastoma protein (pRb) by Cyclin D-CDK4/6 complexes, releasi…
• BDephosphorylation of p53 to stimulate permanent G1 arrest
• CDegradation of DNA polymerase delta by the anaphase-promoting complex
• DInhibition of Cyclin E-CDK2 complexes by unphosphorylated pRb

A sample of double-stranded genomic DNA is analyzed and determined to contain 28% cytosine. According to Chargaff's rules, what percentage of the nitrogenous bases in this DNA sample is adenine?

• A22%
• B28%
• C44%
• D56%

Which enzyme is directly responsible for breaking hydrogen bonds between complementary base pairs to unwind double-stranded DNA at the replication fork?

• ADNA Helicase
• BDNA Ligase
• CDNA Polymerase III
• DTopoisomerase (Gyrase)

Which of the following describes the three essential post-transcriptional processing events required to convert eukaryotic pre-mRNA into mature mRNA?

• A5' 7-methylguanosine capping, 3' polyadenylation (poly-A tail), and spliceosome-mediated…
• B5' polyadenylation, 3' methylguanosine capping, and exon removal
• CHistone methylation, promoter demethylation, and ribosomal subunit binding
• DAnticodon charging, aminoacyl-tRNA synthetase activation, and peptide bond formation

In the standard genetic code, which codon serves as the universal start codon for protein synthesis in eukaryotes, and which amino acid does it encode?

• AAUG, encoding Methionine
• BUAA, encoding Methionine
• CUAG, encoding Tryptophan
• DUGA, encoding Formylmethionine

In prokaryotic DNA replication, which enzymatic property allows DNA Polymerase I to excise RNA primers during lagging-strand processing?

• A5' to 3' exonuclease activity
• B3' to 5' exonuclease activity
• C3' to 5' endonuclease activity
• DRNA-dependent RNA polymerase activity

In a classical Mendelian monohybrid cross between two heterozygous pea plants (Aa x Aa) exhibiting complete dominance, what is the expected phenotypic ratio among the offspring?

• A3 dominant : 1 recessive
• B1 dominant : 2 intermediate : 1 recessive
• C1 dominant : 1 recessive
• D9 dominant : 3 recombinant : 3 recombinant : 1 recessive

Two individuals heterozygous for two independently assorting autosomal genes (AaBb x AaBb) mate. What is the probability that their first child will be homozygous recessive for both traits (aabb)?

• A1/16 (6.25%)
• B3/16 (18.75%)
• C1/4 (25%)
• D9/16 (56.25%)

Hemophilia A is an X-linked recessive bleeding disorder. If a phenotypically normal woman whose father had hemophilia marries a healthy, unaffected man, what is the probability that their first son will have hemophilia?

• A50%
• B25%
• C100%
• D0%

A mother with blood type A (genotype IAi) and a father with blood type B (genotype IBi) have children. Which ABO blood group phenotypes are possible in their offspring?

• AType A, Type B, Type AB, and Type O (each with 25% probability)
• BOnly Type AB and Type O (each with 50% probability)
• COnly Type A and Type B (each with 50% probability)
• DOnly Type AB (100% probability)

Which meiotic error is the primary cytogenetic cause of Down syndrome (Trisomy 21) in approximately 95% of clinical cases?

• AMeiotic non-disjunction of chromosome 21 during gametogenesis (predominantly maternal mei…
• BRobertsonian translocation between chromosomes 14 and 21
• CReciprocal translocation between chromosomes 9 and 22
• DComplete triploidy arising from polyspermy

Which specialized cardiac tissue possesses the highest intrinsic rate of spontaneous diastolic depolarization, making it the normal physiological pacemaker of the human heart?

• ASinoatrial (SA) node
• BAtrioventricular (AV) node
• CBundle of His (Atrioventricular bundle)
• DPurkinje fibers

What is the primary chemical form in which the majority (approximately 70%) of carbon dioxide is transported from peripheral tissues to the lungs in human blood?

• ABicarbonate ions (HCO3-) dissolved in blood plasma
• BCarbaminohemoglobin bound to globin amino groups
• CPhysically dissolved carbon dioxide gas (CO2) in plasma
• DCarbonic acid (H2CO3) bound to albumin

In the human nephron, what is the primary physiological mechanism by which the loop of Henle establishes a hypertonic osmotic gradient in the renal medulla?

• ACountercurrent multiplication: active NaCl reabsorption in the water-impermeable thick as…
• BActive water pumping from the lumen of the ascending limb into the peritubular capillaries
• CPassive filtration of large plasma proteins across the glomerulus into the medullary inte…
• DSelective secretion of glucose and amino acids into the loop of Henle by active symporters

Which gastric cell type secretes hydrochloric acid (HCl) and intrinsic factor, and how is the inactive zymogen pepsinogen converted into active pepsin in the stomach lumen?

• AParietal (oxyntic) cells secrete HCl; the low pH environment induces autocatalytic cleava…
• BChief (zymogenic) cells secrete HCl; intrinsic factor directly cleaves pepsinogen
• CEnteroendocrine G cells secrete HCl; gastrin cleaves pepsinogen into pepsin
• DMucous neck cells secrete HCl; alkaline bicarbonate cleaves pepsinogen

What is the primary ionic event responsible for the rapid upstroke (depolarization phase) of a neuronal action potential?

• ARapid opening of voltage-gated Na+ channels causing massive Na+ influx into the intracell…
• BOpening of voltage-gated K+ channels causing K+ influx into the axon
• COpening of voltage-gated Cl- channels causing Cl- efflux into extracellular fluid
• DInhibition of the Na+/K+ ATPase pump causing passive sodium accumulation

Which endocrine hormone is secreted by beta cells of the Islets of Langerhans in response to elevated blood glucose, and what is its primary metabolic action?

• AInsulin, which stimulates GLUT4 translocation to increase cellular glucose uptake and pro…
• BGlucagon, which stimulates hepatic glycogenolysis and gluconeogenesis
• CSomatostatin, which stimulates pancreatic enzyme secretion and bile release
• DCortisol, which promotes peripheral glucose utilization and lipolysis

According to the Bohr effect in respiratory physiology, which of the following physiological changes causes a rightward shift of the hemoglobin oxygen-dissociation curve, facilitating oxygen release to metabolically active tissues?

• ADecreased pH (increased H+ concentration), increased PCO2, and increased temperature
• BIncreased pH (alkalosis), decreased PCO2, and decreased temperature
• CDecreased 2,3-bisphosphoglycerate (2,3-BPG) concentration and hypothermia
• DDecreased carbon dioxide tension and fetal hemoglobin (HbF) synthesis

Which immunoglobulin isotype is produced as a dimer linked by a J chain and a secretory component, providing the primary adaptive humoral defense at mucosal surfaces, tears, and breast milk?

• ASecretory IgA
• BMonomeric IgG
• CPentameric IgM
• DMonomeric IgE

Which immunological pairing correctly describes antigen presentation via MHC class I and MHC class II molecules?

• AMHC-I presents endogenous cytosolic peptides to CD8+ cytotoxic T cells; MHC-II presents e…
• BMHC-I presents exogenous peptides to CD4+ T cells; MHC-II presents endogenous peptides to…
• CMHC-I is expressed only on professional APCs; MHC-II is expressed on all nucleated cells
• DMHC-I binds antibodies directly; MHC-II activates the alternative complement pathway

During the sliding filament mechanism of skeletal muscle contraction, which ion binds to troponin C to displace tropomyosin and expose myosin-binding sites on actin?

• ACalcium (Ca2+)
• BSodium (Na+)
• CPotassium (K+)
• DMagnesium (Mg2+)

In an ecosystem where primary producers fix 20,000 kJ of solar energy into net primary biomass, approximately how much energy is transferred to and assimilated by secondary consumers, assuming Lindeman's standard 10% trophic efficiency rule?

• A200 kJ
• B2,000 kJ
• C20 kJ
• D10,000 kJ

In the global nitrogen cycle, which biological process describes the aerobic two-step bacterial oxidation of ammonium (NH4+) to nitrite (NO2-) by Nitrosomonas and subsequently to nitrate (NO3-) by Nitrobacter?

• ANitrification
• BNitrogen fixation
• CDenitrification
• DAmmonification

In a human population that is in Hardy-Weinberg equilibrium, an autosomal recessive metabolic disorder affects 4 in 100 individuals (frequency of affected homozygotes q^2 = 0.04). What is the frequency of heterozygous carriers in this population?

• A0.32 (32%)
• B0.16 (16%)
• C0.64 (64%)
• D0.04 (4%)

The anatomical skeletal structure of a human arm, a bat's wing, a cat's foreleg, and a whale's flipper share a common bone arrangement despite serving different functions. What evolutionary phenomenon does this illustrate?

• AHomologous structures resulting from divergent evolution from a common ancestor
• BAnalogous structures resulting from convergent evolution under similar environmental pres…
• CVestigial structures with no developmental ancestral relationship
• DAtavistic structures arising from spontaneous somatic gene duplication

In population ecology, what does the parameter carrying capacity (K) represent in the logistic population growth equation dN/dt = rN(1 - N/K)?

• AThe maximum population size of a species that a given environment can sustainably support…
• BThe intrinsic per capita rate of exponential population increase under unconstrained cond…
• CThe minimum threshold density required to prevent extinction from the Allee effect
• DThe total annual biomass turnover consumed by decomposers

In the hypothalamic-pituitary-thyroid axis, how does elevated circulating free thyroxine (T4) and triiodothyronine (T3) maintain hormonal homeostasis?

• ABy negative feedback inhibition of TRH release from the hypothalamus and TSH release from…
• BBy positive feedback stimulation of TSH release from the posterior pituitary
• CBy direct enzymatic degradation of thyroid peroxidase in thyroid follicular cells
• DBy stimulating calcitonin secretion from parathyroid chief cells

What is the correct ground-state electron configuration of a neutral iron atom (Fe, atomic number Z = 26)?

• A[Ar] 3d6 4s2
• B[Ar] 3d8
• C[Ar] 3d7 4s1
• D[Ar] 3d5 4s2 4p1

Why does neutral phosphorus (P, Z = 15) have a higher first ionization energy (1012 kJ/mol) than its adjacent Period 3 neighbor sulfur (S, Z = 16, 1000 kJ/mol)?

• APhosphorus has a stable, half-filled 3p3 subshell, whereas sulfur has paired electrons in…
• BPhosphorus has a smaller atomic radius than sulfur
• CSulfur has fewer protons in its nucleus than phosphorus
• DThe outer valence electrons in phosphorus experience greater nuclear shielding than those…

Which of the following sets of quantum numbers (n, l, ml, ms) represents a valid, permitted state for an electron residing in a 3d atomic subshell?

• An = 3, l = 2, ml = -1, ms = +1/2
• Bn = 3, l = 3, ml = 0, ms = -1/2
• Cn = 3, l = 2, ml = +3, ms = +1/2
• Dn = 2, l = 2, ml = -2, ms = -1/2

According to VSEPR theory, what is the molecular geometry and hybridization of the central sulfur atom in sulfur tetrafluoride (SF4)?

• ASee-saw geometry with sp3d hybridization
• BTetrahedral geometry with sp3 hybridization
• CSquare planar geometry with sp3d2 hybridization
• DTrigonal bipyramidal geometry with sp3d hybridization

Which of the following pure chemical substances forms intermolecular hydrogen bonds in the liquid state?

• AMethanol (CH3OH)
• BFluoromethane (CH3F)
• CDimethyl ether (CH3OCH3)
• DMethane (CH4)

An organic compound consists of 40.0% Carbon, 6.7% Hydrogen, and 53.3% Oxygen by mass (atomic masses: C = 12.0, H = 1.0, O = 16.0 g/mol). If its experimentally measured molar mass is 180.0 g/mol, what is its molecular formula?

• AC6H12O6
• BCH2O
• CC3H6O3
• DC2H4O2

Aluminum reacts with oxygen gas according to the balanced equation: 4 Al(s) + 3 O2(g) -> 2 Al2O3(s). If 4.0 moles of Al react with 3.0 moles of O2, how many moles of aluminum oxide (Al2O3) are produced?

• A2.0 moles
• B1.5 moles
• C3.0 moles
• D4.0 moles

What is the molarity (mol/L) of an aqueous solution prepared by dissolving 11.7 g of sodium chloride (NaCl, molar mass = 58.5 g/mol) in sufficient distilled water to make a total volume of 500 mL?

• A0.40 M
• B0.20 M
• C0.80 M
• D1.00 M

What volume of concentrated 6.0 M hydrochloric acid (HCl) stock solution is required to prepare exactly 250 mL of 0.48 M dilute HCl solution?

• A20.0 mL
• B12.5 mL
• C40.0 mL
• D50.0 mL

Assuming ideal behavior, what volume will 0.50 moles of nitrogen gas (N2) occupy at standard temperature and pressure (STP: 0 °C and 1.0 atm)?

• A11.2 L
• B22.4 L
• C5.6 L
• D44.8 L

For a chemical reaction that is exothermic (delta H < 0) and results in an increase in entropy (delta S > 0), under what temperature conditions is the reaction thermodynamically spontaneous?

• ASpontaneous at all temperatures
• BSpontaneous only at high temperatures
• CSpontaneous only at low temperatures
• DNon-spontaneous at all temperatures

Given the standard enthalpies of formation: delta Hf(CH4(g)) = -74.8 kJ/mol, delta Hf(CO2(g)) = -393.5 kJ/mol, and delta Hf(H2O(l)) = -285.8 kJ/mol, what is the standard enthalpy of combustion for one mole of methane: CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(l)?

• A-890.3 kJ/mol
• B-604.5 kJ/mol
• C-1039.9 kJ/mol
• D+890.3 kJ/mol

In a kinetic study of the reaction 2 A + B -> C, doubling the initial concentration of reactant A quadruples the reaction rate, while doubling the concentration of reactant B doubles the rate. What is the differential rate law and overall reaction order?

• ARate = k[A]^2[B], overall order 3
• BRate = k[A][B]^2, overall order 3
• CRate = k[A][B], overall order 2
• DRate = k[A]^2[B]^2, overall order 4

How does the addition of a chemical catalyst increase the rate of a reversible chemical reaction?

• AIt provides an alternative reaction pathway with lower activation energy (Ea) for both fo…
• BIt makes the overall reaction enthalpy (delta H) significantly more negative
• CIt shifts the equilibrium position toward higher product yield by increasing Keq
• DIt increases the average kinetic energy of the reacting reactant molecules