Moldova Bacalaureat — Biology (Biologie)

Which pentose sugar is a structural constituent of ribonucleic acid (RNA) and differs from 2-deoxyribose by having a hydroxyl group (-OH) attached to its 2' carbon?

• AGlucose
• BFructose
• CRibose
• DGalactose

What type of covalent chemical bond links adjacent amino acid monomers together during translation on a ribosome?

• APeptide bond
• BPhosphodiester bond
• CGlycosidic bond
• DDisulfide bond

Which nuclear sub-compartment is the primary site of ribosomal RNA (rRNA) transcription and the assembly of ribosomal subunits in eukaryotic cells?

• ANuclear envelope
• BNucleolus
• CNuclear pore complex
• DCentrosome

Which eukaryotic organelle contains acidic hydrolytic enzymes capable of digesting phagocytosed pathogens, damaged organelles, and cellular debris?

• AGolgi apparatus
• BPeroxisome
• CMitochondrion
• DLysosome

Which of the following characteristics distinguishes prokaryotic cells (such as bacteria) from eukaryotic cells?

• AAbsence of membrane-bound organelles and a true nuclear envelope
• BPresence of linear chromosomes enclosed within a nuclear matrix
• CPresence of 80S cytosolic ribosomes and mitochondria
• DPresence of endomembrane compartments including the Golgi apparatus

What is the biological definition of osmosis across a living cell membrane?

• AMovement of solute molecules against an electrochemical gradient using ATP hydrolysis
• BTransport of large macromolecules via endocytic vesicle engulfment
• CNet diffusion of water molecules across a selectively permeable membrane toward a region…
• DCarrier-mediated facilitated diffusion of ions down their concentration gradient

During which phase of mitosis do sister chromatids cleave their centromeric cohesin links and move toward opposite poles of the mitotic spindle?

• AProphase
• BAnaphase
• CTelophase
• DMetaphase

In the glycolytic pathway taking place in the eukaryotic cytosol, what is the net yield of ATP and reduced nicotinamide adenine dinucleotide (NADH) per single molecule of glucose oxidized to two pyruvate molecules?

• A4 net ATP and 4 NADH
• B2 net ATP and 0 NADH
• C1 net ATP and 2 NADH
• D2 net ATP and 2 NADH

According to the Singer-Nicolson fluid mosaic model, what is the primary structural role of cholesterol within eukaryotic animal plasma membranes?

• AIt acts as a bidirectional fluidity buffer, restraining phospholipid movement at elevated…
• BIt provides direct enzymatic hydrolysis of ATP to drive primary active transport across t…
• CIt forms the hydrophilic pore lining that facilitates continuous passive diffusion of wat…
• DIt binds to extracellular peptide hormones to initiate second-messenger signal cascades

Which of the following cellular physiological functions is predominantly carried out by the smooth endoplasmic reticulum (SER) rather than the rough endoplasmic reticulum (RER)?

• ASynthesis of secretory proteins and insertion of signal peptides
• BN-linked core glycosylation of nascent lysosomal hydrolases
• CSynthesis of lipids (including phospholipids and steroid hormones), detoxification of hyd…
• DSynthesis of ribosomal RNA and maturation of the 60S ribosomal subunit

During which substage of Prophase I in meiosis does crossing over (genetic recombination between non-sister chromatids of homologous chromosomes) occur?

• ALeptotene
• BPachytene
• CDiplotene
• DDiakinesis

Under anaerobic conditions, what is the primary metabolic purpose of reducing pyruvate to lactate in human skeletal muscle or to ethanol in brewer's yeast?

• ATo re-oxidize NADH back to NAD+, ensuring a continuous supply of NAD+ to sustain glycolys…
• BTo directly synthesize 3 additional molecules of ATP via oxidative phosphorylation
• CTo transport pyruvate across the outer mitochondrial membrane into the matrix
• DTo eliminate toxic carbon dioxide gas from rapidly contracting muscle fibers

A diploid mammalian somatic cell has 2n = 24 chromosomes. What are the exact numbers of chromosomes and sister chromatids present per cell during (1) Metaphase I of meiosis and (2) Anaphase II of meiosis, respectively?

• AMetaphase I: 12 chromosomes, 24 chromatids; Anaphase II: 12 chromosomes, 12 chromatids
• BMetaphase I: 24 chromosomes, 48 chromatids; Anaphase II: 24 chromosomes, 0 chromatids (se…
• CMetaphase I: 48 chromosomes, 48 chromatids; Anaphase II: 12 chromosomes, 24 chromatids
• DMetaphase I: 24 chromosomes, 24 chromatids; Anaphase II: 24 chromosomes, 48 chromatids

A biochemical analysis reveals that a purified double-stranded DNA sample contains 28% cytosine by molar nucleotide composition. According to Chargaff's rules, what are the percentages of adenine and total purines in this sample?

• AAdenine = 28%, Total purines = 28%
• BAdenine = 44%, Total purines = 50%
• CAdenine = 22%, Total purines = 50%
• DAdenine = 22%, Total purines = 44%

Which set of cellular and structural characteristics uniquely defines organisms classified in the Kingdom Monera (Bacteria)?

• AUnicellular prokaryotes with peptidoglycan cell walls, circular DNA lacking a nuclear env…
• BMulticellular eukaryotes with chitinous cell walls and absorptive heterotrophic nutrition
• CUnicellular eukaryotes possessing membrane-bound chloroplasts and cellulosic walls
• DMulticellular photoautotrophs displaying alternation of heteromorphic generations

Which plant vascular tissue is responsible for conducting water and dissolved mineral nutrients upward from roots to leaves, and what is its cellular state at functional maturity?

• APhloem sieve tube elements, which are living cells lacking nuclei
• BCollenchyma fibers, which are living elongated cells with unevenly thickened primary walls
• CXylem tracheids and vessel elements, which are dead hollow cells with lignified secondary…
• DParenchyma ground tissue, which consists of dividing totipotent meristematic cells

What fundamental anatomical and reproductive feature distinguishes Angiosperms (flowering plants) from Gymnosperms (conifers and cycads)?

• AGymnosperms possess true flowers and produce triploid endosperm
• BGymnosperms produce flagellated motile spores instead of seeds
• CAngiosperms lack vascular tissues and produce seeds on exposed cone scales
• DAngiosperms produce seeds enclosed within a protective carpel (ovary that matures into a…

Which of the following animal taxa possesses an open circulatory system in which hemolymph directly bathes organs within a hemocoel?

• AAnnelids (earthworms)
• BArthropods (insects, crustaceans, and arachnids)
• CCephalopods (squid and octopuses)
• DVertebrates (mammals and birds)

What is the primary nitrogenous waste product excreted by freshwater bony fish (teleosts), and why does it contrast with the uric acid excreted by birds and reptiles?

• AAmmonia; it is highly toxic and water-soluble, easily flushed out across gills in aquatic…
• BUrea; it requires large amounts of ATP to produce but is completely non-polar and excrete…
• CGuanine; it is soluble only in acidic solutions and precipitates within swim bladders
• DUric acid; it is highly toxic to fish embryos and requires continuous water ingestion

Which secondary lateral meristem in woody dicot stems produces secondary xylem toward the interior and secondary phloem toward the exterior?

• AApical meristem
• BCork cambium (phellogen)
• CVascular cambium
• DIntercalary meristem

What nutritional mode and cell wall composition define organisms belonging to Kingdom Fungi?

• APhotoautotrophic nutrition with cellulosic cell walls
• BAbsorptive heterotrophic nutrition (osmotrophy) with chitinous cell walls
• CPhagotrophic ingestive heterotrophy lacking cell walls
• DChemoautotrophic nutrition with peptidoglycan walls

How do terrestrial insects deliver oxygen directly to respiring cells without relying on their circulatory system?

• AThrough closed book lungs containing hemolymph channels
• BVia cutaneous respiration across a moist mucous cuticle
• CBy utilizing branchial gill filaments ventilated through an operculum
• DVia a branching tracheal system of air-filled tubes opening to the exterior through spira…

Which of the following comparative anatomical descriptions correctly reflects the evolutionary transition of vertebrate hearts from amphibians to mammals?

• AAmphibians possess a 3-chambered heart (two atria, one ventricle) with partial mixing of…
• BAmphibians possess a 2-chambered single-circulation heart, whereas mammals have a 3-chamb…
• CAmphibians possess a 4-chambered heart with a foramen of Panizza, whereas mammals possess…
• DAmphibians possess two ventricles and one atrium, whereas mammals have two atria and one…

Which excretory structures do terrestrial insects employ to secrete uric acid and maintain osmoregulation, and into which organ do they empty?

• AMalpighian tubules, which extract uric acid and solutes from hemolymph and empty into the…
• BMetanephridia, which filter coelomic fluid and empty through nephridiopores on the ventra…
• CProtonephridia with flame cells, which drain metabolic waste directly into the pharynx
• DAntennal green glands, which discharge urine through pores located at the base of the ant…

In the evolutionary alternation of generations of land plants, how do Bryophytes (mosses) differ from Pteridophytes (ferns) regarding the dominant, nutritionally independent life stage?

• ABryophytes have a dominant diploid sporophyte; Pteridophytes have a dominant haploid game…
• BBoth Bryophytes and Pteridophytes have dominant triploid endosperms
• CBryophytes have a dominant haploid (n) gametophyte with the sporophyte dependent on it; P…
• DNeither group exhibits alternation of generations, reproducing exclusively via vegetative…

During the depolarization phase of a neuronal action potential, which ion channels open, and in which direction do the ions move?

• AVoltage-gated K+ channels open, allowing K+ to exit the neuron
• BLigand-gated Cl- channels open, allowing Cl- to enter the axon
• CVoltage-gated Na+ channels open, allowing Na+ to rush into the intracellular fluid down i…
• DATP-driven Ca2+ pumps activate, pumping Ca2+ into the synaptic cleft

In the human circulatory system, which cardiovascular pathway carries deoxygenated blood from the heart to the lungs for gas exchange?

• AThe pulmonary trunk and pulmonary arteries emerging from the right ventricle
• BThe aorta emerging from the left ventricle
• CThe pulmonary veins entering the left atrium
• DThe superior and inferior venae cavae entering the right atrium

By which physical transport mechanism does external gas exchange (O2 and CO2 transfer) occur across the alveolar-capillary respiratory membrane in human lungs?

• AReceptor-mediated endocytosis into type II alveolar pneumocytes
• BPrimary active transport driven by ATP-dependent gas pumps
• CFacilitated diffusion through specialized gas-carrier transmembrane proteins
• DSimple passive diffusion down partial pressure (concentration) gradients

Which endocrine hormone is secreted by the beta cells of the pancreatic islets of Langerhans in response to elevated blood glucose levels?

• AGlucagon
• BInsulin
• CSomatostatin
• DEpinephrine

In which anatomical section of the human gastrointestinal tract does the vast majority of chemical digestion and nutrient absorption occur?

• AEsophagus
• BStomach
• CSmall intestine (duodenum, jejunum, and ileum)
• DLarge intestine (colon)

Which two anatomical organs are classified as the primary lymphoid organs responsible for the production and initial maturation of immunocompetent B and T lymphocytes in humans?

• ASpleen and lymph nodes
• BRed bone marrow and the thymus gland
• CTonsils and Peyer's patches
• DAppendix and adenoids

In the hypothalamic-pituitary-thyroid (HPT) endocrine axis, what negative feedback loop operates when free circulating blood levels of triiodothyronine (T3) and thyroxine (T4) exceed homeostatic set points?

• AElevated T3/T4 stimulate the posterior pituitary to secrete oxytocin and prolactin
• BElevated T3/T4 stimulate parathyroid glands to release parathyroid hormone (PTH)
• CElevated T3/T4 stimulate the anterior pituitary to secrete more thyroid-stimulating hormo…
• DElevated free T3 and T4 act on the anterior pituitary to inhibit TSH secretion and on the…

Which of the following statements correctly differentiates humoral immunity from cell-mediated adaptive immunity?

• AHumoral immunity is mediated by B lymphocytes differentiating into antibody-secreting pla…
• BHumoral immunity relies exclusively on natural killer (NK) cells, whereas cell-mediated i…
• CHumoral immunity is non-specific and lacks immunological memory, whereas cell-mediated im…
• DHumoral immunity operates exclusively in mucosal linings, whereas cell-mediated immunity…

How do liver bile salts and pancreatic enzymes coordinate the digestion and absorption of dietary triglycerides in the small intestine?

• ABile salts hydrolyze peptide bonds directly, while pepsin digests neutral triglycerides i…
• BBile salts convert fatty acids into water-soluble glucose via gluconeogenesis in the brus…
• CAmphipathic bile salts emulsify large lipid droplets into small emulsion droplets, increa…
• DTriglycerides are absorbed intact into intestinal capillaries by primary active ATP pumps…

In the human female menstrual cycle, what endocrine event directly triggers ovulation (rupture of the mature Graafian follicle and release of the secondary oocyte)?

• AA sudden drop in blood progesterone levels causing endometrial sloughing
• BA sharp peak in human chorionic gonadotropin (hCG) secreted by the placenta
• CContinuous suppression of follicle-stimulating hormone (FSH) by inhibin B
• DA dramatic mid-cycle surge in Luteinizing Hormone (LH) induced by sustained high levels o…

Which of the following statements accurately characterizes the functional and anatomical differences between rod and cone photoreceptor cells in the human retina?

• ARods contain rhodopsin, exhibit high sensitivity to low light (scotopic monochromatic vis…
• BRods mediate three distinct color wavelengths (red, green, blue) exclusively within the o…
• CRods are myelinated multipolar neurons that transmit action potentials along the optic tr…
• DCones lack photopigments and detect light via mechanical vibration of retinal ciliated ha…

What is the mechanical and sensory mechanism of auditory transduction within the cochlea of the human inner ear?

• ADirect electromagnetic resonance of auditory ossicles transmitting radio frequencies to t…
• BSemicircular canal otolith displacement stimulating macula hair cells during angular head…
• CSound waves vibrate the tympanic membrane and ossicles, causing the stapes footplate to d…
• DAir travels directly through the Eustachian tube to vibrate the auditory cortex directly

What primary etiological and pathophysiological difference distinguishes Type 1 diabetes mellitus from Type 2 diabetes mellitus?

• AType 1 is characterized by autoimmune destruction of pancreatic beta cells causing absolu…
• BType 1 is caused exclusively by excessive dietary sugar intake in elderly patients, where…
• CType 1 results from overproduction of glucagon by alpha cells, whereas Type 2 results fro…
• DType 1 is completely reversible through simple lifestyle modifications, whereas Type 2 re…

Under what immunological and parental blood type conditions can Erythroblastosis Fetalis (Hemolytic Disease of the Fetus and Newborn, HDFN) occur during pregnancy?

• AWhen an Rh-positive mother carries an Rh-negative fetus during her first pregnancy
• BWhen an O-negative mother carries an O-positive fetus and produces IgM antibodies that cr…
• CWhen an Rh-negative mother is sensitized to the Rh (D) antigen by an Rh-positive first fe…
• DWhen both parents are Rh-negative and the fetus undergoes spontaneous gene mutation to be…

What is the genetic principle stated by Gregor Mendel's First Law (the Law of Segregation)?

• AThe two alleles for a heritable gene segregate during gamete formation (meiosis) so that…
• BAlleles of two or more different genes sort independently into gametes regardless of thei…
• CDominant alleles are always more frequent in natural biological populations than recessiv…
• DNon-homologous chromosomes fuse together during anaphase to produce diploid gametes

In a standard Mendelian monohybrid cross between two true-breeding pea plant lines (one homozygous dominant with purple flowers, AA, and one homozygous recessive with white flowers, aa), what is the expected phenotypic ratio in the F2 generation following self-fertilization of the F1 hybrids?

• A1 purple : 1 white
• B9 purple : 3 white : 3 pink : 1 yellow
• C3 purple : 1 white
• D1 purple : 2 pink : 1 white

Which three-nucleotide mRNA codon functions as the universal start codon in eukaryotic translation, and which amino acid does it encode?

• AUAA, encoding Valine
• BUAG, encoding Tryptophan
• CUGA, encoding Leucine
• DAUG, encoding Methionine

What is the core premise of Charles Darwin's theory of evolution by natural selection?

• AOrganisms acquire beneficial traits through physical exercise during their lifetime and p…
• BIndividuals within a population exhibit heritable variations, and those possessing traits…
• CAll species were created simultaneously and remain immutable over geological epochs
• DGenetic drift randomly fixes maladaptive mutations in large equilibrium populations

According to Raymond Lindeman's 10% ecological rule, approximately what percentage of energy is transferred from one trophic level to the next higher level in a terrestrial food chain?

• AApproximately 10% (the remaining ~90% is dissipated as metabolic heat, respiration, and u…
• BExactly 50% (half goes to growth and half to excretion)
• C100% (energy is completely conserved according to the first law of thermodynamics)
• DLess than 0.1% (all energy is lost to gravity)

What complementary base-pairing rules govern double-stranded DNA structure, and how many hydrogen bonds form between each pair?

• AAdenine pairs with Guanine via 1 bond; Cytosine pairs with Thymine via 4 bonds
• BAdenine pairs with Uracil via 2 bonds; Guanine pairs with Thymine via 3 bonds
• CAdenine pairs with Thymine via 2 hydrogen bonds; Guanine pairs with Cytosine via 3 hydrog…
• DAdenine pairs with Cytosine via 3 bonds; Guanine pairs with Thymine via 2 bonds

What is the defining ecological difference between primary ecological succession and secondary ecological succession?

• APrimary succession occurs exclusively in deep oceanic trenches, whereas secondary success…
• BPrimary succession initiates on newly exposed, virgin substrate completely devoid of soil…
• CPrimary succession is driven exclusively by climax trees, whereas secondary succession is…
• DPrimary succession takes only 2 to 3 weeks, whereas secondary succession requires million…

In the global biogeochemical nitrogen cycle, which biological process converts inert atmospheric dinitrogen gas (N2) into bioavailable ammonia (NH3 / NH4+)?

• ANitrification
• BDenitrification
• CAmmonification (mineralization)
• DBiological nitrogen fixation