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100+ Free OBB Practice Questions

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Sample OBB Practice Questions

Try these sample questions to test your OBB exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1The sodium-potassium pump (Na+/K+-ATPase) is a primary active transport P-type ATPase essential for maintaining resting membrane potential and cellular volume in animal cells. During its catalytic cycle, what sequence of conformational transitions and ion stoichiometric exchanges occurs across the plasma membrane?
A.Phosphorylation by ATP in the E1 conformation triggers a transition to the E2 conformation, expelling 3 Na+ ions into the extracellular fluid and subsequently importing 2 K+ ions into the cytosol upon dephosphorylation
B.Dephosphorylation of the catalytic alpha-subunit in the cytosolic E2 state facilitates the simultaneous export of 2 Na+ ions down their electrochemical gradient and import of 3 K+ ions against their gradient via passive leakage channels
C.Binding of cytosolic ATP in the open E2 state induces immediate non-covalent opening of a hydrophilic pore that allows 3 Na+ ions and 3 K+ ions to exchange via electroneutral facilitated counter-transport without generating any net charge displacement across the membrane bilayer
D.Phosphorylation by cytosolic GTP drives the continuous mechanical rotation of beta-subunits from an outward-facing E1 state, transporting 2 Na+ ions outward and 1 K+ ion inward with the stoichiometric release of inorganic pyrophosphate into the extracellular fluid
Explanation: The Na+/K+-ATPase operates via an E1/E2 alternating access mechanism (Post-Albers cycle). In the E1 state facing the cytosol, it binds 3 Na+ ions with high affinity and is phosphorylated by ATP at a conserved aspartate residue; the resulting conformational change to the E2 state releases 3 Na+ extracellularly, binds 2 extracellular K+ ions, and subsequent dephosphorylation returns the pump to the E1 state to release 2 K+ into the cytosol.
2The fluid mosaic model explains the dynamic structural organization of biological membranes. When poikilothermic organisms experience an abrupt decrease in environmental temperature, which homeoviscous adaptation is rapidly implemented to prevent phase transition of membrane lipids into a rigid, non-functional gel state?
A.Increasing the saturation of phospholipid hydrocarbon tails by converting cis-unsaturated oleic acid chains into fully saturated stearic acid chains, thereby enhancing van der Waals packing density
B.Incorporating a higher proportion of unsaturated fatty acyl chains containing cis-double bonds and modulating cholesterol content to disrupt tight acyl packing
C.Eliminating integral transmembrane proteins from lipid rafts to permit the spontaneous lateral crystallization of sphingomyelins and glycolipids into hexagonal gel clusters
D.Synthesizing longer-chain saturated fatty acids that maximize hydrophobic van der Waals interactions between adjacent phospholipid leaflets to solidify the membrane core
Explanation: To maintain optimal membrane fluidity at lower temperatures (homeoviscous adaptation), cells increase the proportion of cis-unsaturated fatty acids, whose permanent kinks prevent tight paracrystalline packing of acyl chains. Cholesterol acts as a bidirectional fluidity buffer, interfering with tight acyl chain packing at low temperatures and restricting excessive lipid movement at high temperatures.
3In steady-state enzyme kinetics described by the Michaelis-Menten formulation, an experimenter evaluates the effect of adding a reversible inhibitor to an enzymatic reaction. Lineweaver-Burk double-reciprocal plot analysis reveals that the lines obtained in the presence and absence of the inhibitor intersect precisely at the positive y-axis (same 1/Vmax). What type of inhibition is occurring, and how are the kinetic parameters affected?
A.Non-competitive inhibition, where the inhibitor binds equally to the free enzyme and ES complex at an allosteric site, reducing Vmax while leaving the apparent Km completely unchanged across all substrate concentrations
B.Uncompetitive inhibition, where the inhibitor binds exclusively to the enzyme-substrate (ES) complex, causing a parallel shift in the Lineweaver-Burk plot and a proportional decrease in both apparent Km and apparent Vmax
C.Competitive inhibition, where the inhibitor competes with the substrate for the active site, increasing the apparent Km while leaving the maximum velocity (Vmax) unchanged
D.Irreversible suicide inhibition, where a covalent adduct forms permanently at the catalytic triad, reducing active enzyme concentration without altering substrate affinity of the remaining uninhibited enzyme pool
Explanation: In competitive inhibition, the inhibitor structurally resembles the substrate and competes directly for the free enzyme's active site. At saturating substrate concentrations, the substrate outcompetes the inhibitor, allowing the enzyme to achieve its original maximum velocity (Vmax unchanged; identical 1/Vmax y-intercept), while a higher substrate concentration is required to reach half-maximal velocity (apparent Km increases; 1/Km x-intercept shifts closer to the origin).
4Phosphofructokinase-1 (PFK-1) catalyzes the committed step of glycolysis, converting fructose 6-phosphate and ATP into fructose 1,6-bisphosphate and ADP. How is PFK-1 allosterically regulated in mammalian hepatocytes to coordinate carbon flux with energy demand and hormonal signaling?
A.High concentrations of ATP and citrate allosterically activate PFK-1 by stabilizing the high-affinity R-state conformation, whereas elevated AMP and glucagon strongly inhibit the enzyme to stimulate hepatic glycolysis during nutrient deprivation
B.Fructose 2,6-bisphosphate acts as a potent competitive inhibitor of PFK-1 by occupying the catalytic fructose 6-phosphate binding pocket, while high cellular AMP levels promote its ubiquitination and rapid degradation by the 26S proteasome
C.Glucagon stimulates PFK-1 by promoting the kinase activity of the bifunctional enzyme PFK-2/FBPase-2, thereby elevating intracellular levels of fructose 2,6-bisphosphate to accelerate glycolytic carbon disposal during fasting states
D.High physiological ATP and cytosolic citrate allosterically inhibit PFK-1, whereas elevated AMP and fructose 2,6-bisphosphate relieve ATP inhibition to stimulate glycolysis
Explanation: PFK-1 is the primary flux-controlling valve of glycolysis. High concentrations of ATP (acting at an allosteric regulatory site distinct from the catalytic site) and citrate inhibit PFK-1, signaling abundant energy and biosynthetic precursors; conversely, elevated AMP and fructose 2,6-bisphosphate (produced by insulin-stimulated PFK-2) act as powerful allosteric activators that overcome ATP inhibition and accelerate glycolytic flux.
5During mitochondrial oxidative phosphorylation, Complex IV (cytochrome c oxidase) catalyzes the terminal electron transfer reaction of the respiratory chain. What are the specific molecular substrates, prosthetic metal centers, and proton translocation characteristics of this enzyme?
A.Four reduced cytochrome c molecules transfer 4 electrons through CuA, heme a, and the binuclear heme a3-CuB center to reduce one O2 to 2 H2O, pumping 4 H+ into the intermembrane space
B.Two reduced ubiquinol (QH2) molecules transfer 4 electrons through iron-sulfur Rieske centers directly to elemental oxygen, translocating 8 H+ across the outer mitochondrial membrane into the surrounding cytosol
C.Reduced NADH directly donates 2 electrons to an internal FMN prosthetic group within Complex IV, which passes them to cytochrome c with the obligate uptake of 4 matrix protons per oxygen atom reduced to peroxide
D.Four oxidized cytochrome c molecules abstract 4 hydride ions from molecular oxygen, translocating 2 H+ into the mitochondrial matrix to generate stable hydrogen peroxide intermediates within the intermembrane space
Explanation: Complex IV accepts 4 electrons sequentially from 4 reduced cytochrome c molecules at its binuclear CuA site. Electrons are relayed through heme a to the catalytic binuclear center (heme a3-CuB), where a molecule of O2 is bound and reduced to 2 molecules of H2O using 4 matrix protons (chemical/scalar protons), while 4 additional protons are translocated (pumped) across the inner mitochondrial membrane into the intermembrane space.
6Brown adipose tissue (BAT) plays a pivotal role in non-shivering thermogenesis in mammalian neonates and hibernating mammals. What is the precise biochemical mechanism by which uncoupling protein 1 (UCP-1 / thermogenin) produces heat in the inner mitochondrial membrane?
A.It accelerates ATP synthesis by forcing the F0F1-ATP synthase rotor to spin at an uncoupled, hyperactive rate that dissipates mechanical kinetic energy directly as radiant frictional heat
B.It provides a regulated pathway for protons to leak from the intermembrane space back into the mitochondrial matrix, dissipating the proton-motive force as heat without generating ATP
C.It hydrolyzes newly formed ATP molecules in the mitochondrial matrix at an exceptionally rapid rate, liberating the standard Gibbs free energy of phosphate anhydride bonds as metabolic heat
D.It selectively inhibits Complex IV of the electron transport chain, causing high-energy electrons to jump directly to matrix molecular oxygen to produce abundant heat-generating superoxide radicals
Explanation: UCP-1 (thermogenin) is an inner mitochondrial membrane channel that short-circuits the electrochemical proton gradient. By allowing protons to flow down their electrochemical gradient from the intermembrane space directly back into the matrix bypassing the F0F1-ATP synthase, the stored potential energy of the proton-motive force is dissipated entirely as heat rather than captured as chemical energy in ATP.
7Proteins destined for secretion, incorporation into the plasma membrane, or delivery to lysosomes are targeted to the rough endoplasmic reticulum (RER). Which molecular component directly recognizes the hydrophobic N-terminal signal peptide as it emerges from the ribosome and halts translation until docking occurs?
A.The Sec61 heterotrimeric translocon complex embedded directly within the outer leaflet of the nuclear envelope that forms an aqueous protein-conducting channel
B.The signal peptidase complex located on the cytosolic face of the smooth endoplasmic reticulum tubular network that cleaves targeting presequences prior to docking
C.The Signal Recognition Particle (SRP), a cytosolic ribonucleoprotein complex that binds the signal peptide and arrests elongation
D.The BIP/GRP78 molecular chaperone residing in the ER lumen that actively pulls nascent polypeptide chains through the membrane pore via rounds of ATP hydrolysis
Explanation: The Signal Recognition Particle (SRP) is a cytosolic ribonucleoprotein complex that recognizes and binds the hydrophobic N-terminal signal sequence as it emerges from the exit tunnel of the translating ribosome. SRP binding causes a temporary pause in translation (elongation arrest) and guides the ribosome-nascent chain complex to the RER membrane by binding the SRP receptor, allowing co-translational translocation through the Sec61 channel.
8Intracellular vesicular transport between the endoplasmic reticulum, the Golgi apparatus, and the plasma membrane relies on distinct protein coat complexes. What are the specific directional trafficking pathways mediated by COPI, COPII, and clathrin coats, respectively?
A.COPI mediates anterograde transport from ER to Golgi; COPII mediates retrograde transport from Golgi to ER; clathrin mediates nuclear import through the nuclear pore complex
B.COPI mediates endocytosis at the plasma membrane; COPII mediates lysosomal biogenesis; clathrin mediates retrograde transport from trans-Golgi cisternae back to the endoplasmic reticulum network
C.COPI mediates vesicular fusion with peroxisomes; COPII mediates post-translational transport to chloroplasts; clathrin mediates autophagosome maturation and fusion with multivesicular bodies
D.COPI mediates retrograde transport from Golgi back to ER; COPII mediates anterograde transport from ER to cis-Golgi; clathrin mediates trans-Golgi and endocytic pathways
Explanation: Vesicle coat proteins direct specific trafficking routes: COPII mediates anterograde (forward) transport from the rough ER to the cis-Golgi network; COPI mediates retrograde (retrieval) transport from the Golgi back to the ER as well as intra-Golgi cisternae retrieval; and clathrin mediates vesicle budding from the trans-Golgi network to endosomes/lysosomes as well as receptor-mediated endocytosis at the plasma membrane.
9In the light reactions of oxygenic photosynthesis in chloroplast thylakoid membranes, what determines whether electrons undergo non-cyclic (linear) photophosphorylation or cyclic photophosphorylation around Photosystem I?
A.High concentrations of plastoquinone in the oxidized state force electrons to bypass Photosystem I entirely, reducing cytochrome b6f without absorbing far-red photons at P700
B.A high ratio of stromal NADPH to NADP+ favors the diversion of ferredoxin electrons back to the plastoquinone pool/cytochrome b6f complex, generating additional ATP without producing NADPH
C.Low light intensity triggers the complete dissociation of the oxygen-evolving manganese complex from Photosystem II, shutting down linear electron flow permanently throughout the daytime
D.High luminal ATP concentrations allosterically inhibit ferredoxin-NADP+ reductase (FNR), forcing ferredoxin to directly hydrolyze water molecules at Photosystem I to regenerate proton gradients
Explanation: When stromal NADPH levels are high and NADP+ is scarce (or when the Calvin cycle requires additional ATP relative to NADPH), ferredoxin donates electrons back to the plastoquinone (PQ) pool via cyclic electron flow involving PGR5/PGRL1 or the NDH complex. Electrons flow from PQ through the cytochrome b6f complex back to PSI, pumping protons into the thylakoid lumen to synthesize ATP via chemiosmosis without generating NADPH or evolving O2.
10When Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) acts as an oxygenase under conditions of high temperature and low intracellular CO2/O2 ratios, photorespiration (the C2 oxidative photosynthetic carbon cycle) is initiated. What metabolic salvage pathway coordinates the recovery of carbon across three distinct cellular compartments?
A.Phosphoglycolate is converted directly into oxaloacetate in the chloroplast stroma, transported to the peroxisome for malate reduction, and decarboxylated in the mitochondrion by pyruvate dehydrogenase to regenerate acetyl-CoA and fuel oxidative phosphorylation
B.Phosphoglycolate undergoes direct beta-oxidation in the peroxisome, generating acetyl-CoA molecules that enter the mitochondrial Krebs cycle to synthesize glucose via hepatic-like gluconeogenic pathways in plant leaves
C.Phosphoglycolate is dephosphorylated in the chloroplast, oxidized to glyoxylate and transaminated to glycine in the peroxisome, converted to serine with CO2 release in the mitochondrion, and returned to the chloroplast as glycerate
D.Phosphoglycolate is exported into the cytosol, where it is condensed with phosphoenolpyruvate by PEP carboxylase to regenerate ribulose-1,5-bisphosphate without any carbon or nitrogen loss across compartments
Explanation: Photorespiration begins when Rubisco adds O2 to RuBP, forming 1 molecule of 3-phosphoglycerate and 1 molecule of 2-phosphoglycolate. The salvage pathway dephosphorylates 2-phosphoglycolate to glycolate in the chloroplast, transports it to the peroxisome where glycolate oxidase produces glyoxylate and transaminases make glycine; two glycines condense in the mitochondrion (via glycine decarboxylase and serine hydroxymethyltransferase) to yield 1 serine, 1 CO2, and 1 NH3; serine is then converted to glycerate in the peroxisome and phosphorylated to 3-PGA in the chloroplast.

About the OBB Exam

The Olimpíada Brasileira de Biologia (OBB) is Brazil's official national biology competition for secondary school students, organized and administered by the Instituto Butantan. Aligned with the International Biology Olympiad (IBO) syllabus, the OBB aims to stimulate student interest in the life sciences, discover exceptional young scientific talent, and serve as the premier qualifying benchmark for Brazilian biological science education. Under the 2026 Instituto Butantan regulation, the competition is structured into three national elimination stages: Stage 1 features 25 multiple-choice questions administered in a 30-minute-to-2-hour online testing window; Stage 2 features 30 multiple-choice questions for qualifying students; and Stage 3 features 25 true/false sentences. Top national medalists earn certificates of academic excellence, qualify for Olympic spots (Vagas Olímpicas) for direct university admission at prestigious Brazilian universities such as USP, UNICAMP, and UNESP without traditional entrance exams, and earn eligibility for the separate post-OBB international training and selection process (Capacitação e Seletiva IBO/OIAB). This practice bank offers an English-language study adaptation comprising 100 in-depth practice questions spanning cell biology, molecular genetics, animal and human physiology, plant biology, ecology, and evolutionary systematics.

Assessment

Three sequential national elimination stages: Stage 1 (25 MCQs, 30-minute to 2-hour window), Stage 2 (30 MCQs, 30-minute to 2-hour window for Stage 1 qualifiers), and Stage 3 (25 true/false sentences, 30-minute to 2-hour window). This practice bank provides 100 comprehensive practice questions in English covering the entire OBB syllabus.

Time Limit

30-minute to 2-hour window per elimination stage

Passing Score

Rank-based national qualification cutoffs determined by Instituto Butantan

Exam Fee

Free (Gratuito) (Instituto Butantan)

OBB Exam Content Outline

Not published

Biologia Celular e Molecular

Structure and dynamics of biomembranes, lipid bilayers, membrane transport mechanisms (passive diffusion, facilitated transport, primary and secondary active transport, endocytosis/exocytosis); structural and functional organization of eukaryotic organelles (nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria, and chloroplasts); protein sorting, targeting, and vesicular trafficking; enzyme kinetics (Michaelis-Menten kinetics, Km, Vmax, Lineweaver-Burk plots, competitive, non-competitive, and uncompetitive inhibition, allosteric regulation); bioenergetics and cellular respiration (glycolysis, pyruvate oxidation, citric acid cycle, mitochondrial electron transport chain, chemiosmotic ATP synthesis, and metabolic uncoupling); photosynthetic light reactions and Calvin-Benson cycle; intracellular signaling pathways (G-protein coupled receptors, receptor tyrosine kinases, second messengers such as cAMP, IP3, DAG, and Ca2+).

Not published

Genética e Biologia Molecular

Classical Mendelian inheritance patterns (monohybrid and dihybrid crosses, incomplete dominance, codominance, multiple alleles, lethal genes, epistasis, and pleiotropy); chromosome theory of inheritance, sex linkage, sex-influenced traits, and pedigree analysis; gene linkage, crossing over, recombination frequency, and three-point testcross chromosome mapping; molecular mechanisms of DNA replication (helicases, topoisomerases, single-strand binding proteins, primases, DNA polymerases, Okazaki fragments, and ligases); prokaryotic and eukaryotic transcription, promoter recognition, and RNA processing (5' capping, splicing, polyadenylation); translation, tRNA charging, and the genetic code (wobble hypothesis); prokaryotic gene regulation (lac and trp operons) and eukaryotic epigenetic mechanisms (DNA methylation, histone acetylation, non-coding RNAs); recombinant DNA technology, PCR, Sanger and next-generation sequencing, CRISPR-Cas9 genome editing, and quantitative genetics.

Not published

Anatomia e Fisiologia Animal e Humana

Comparative animal histology and organ system physiology; neurophysiology (resting membrane potential, Goldman-Hodgkin-Katz equation, action potential generation and propagation, synaptic transmission, neurotransmitters, and neuromuscular junctions); cardiovascular hemodynamics (cardiac cycle, electrocardiography, cardiac output regulation, Frank-Starling law, blood pressure control, and baroreceptor reflexes); respiratory physiology (ventilation mechanics, pulmonary compliance, gas exchange, and hemoglobin oxygen dissociation curves with Bohr and Haldane effects); renal physiology and osmoregulation (glomerular filtration rate, tubular reabsorption/secretion, countercurrent multiplication in the loop of Henle, and the renin-angiotensin-aldosterone system); endocrine regulation (hypothalamic-pituitary axes, thyroid, adrenal, pancreatic hormones, and calcium homeostasis); immunology (innate physical/chemical defenses, pattern recognition receptors, complement pathways, adaptive cell-mediated and humoral immunity, MHC Class I/II presentation, clonal selection, and immunological memory).

Not published

Anatomia e Fisiologia Vegetal

Plant tissue organization (meristems, parenchyma, collenchyma, sclerenchyma, xylem, phloem, and periderm); water relations and transport mechanisms (water potential components, transpiration-cohesion-tension theory, root pressure, guttation, and stomatal aperture regulation); phloem translocation (pressure-flow hypothesis, apoplastic and symplastic loading, source-to-sink partitioning); photosynthetic adaptations and leaf anatomy (C3 pathway, C4 pathway with Kranz anatomy and PEP carboxylase, and Crassulacean Acid Metabolism / CAM temporal carbon fixation); plant mineral nutrition, nitrogen assimilation, and mycorrhizal/rhizobial symbioses; phytohormone signaling and physiological functions (auxins and polar transport, gibberellins, cytokinins, abscisic acid, and ethylene); plant development, photoperiodism, phytochrome photoreceptors (Pr/Pfr transitions), vernalization, and tropisms (phototropism, gravitropism, thigmotropism).

Not published

Ecologia e Biodiversidade

Population ecology (exponential and logistic growth models, carrying capacity, r- and K-selection strategies, age pyramids, and life tables); community ecology (interspecific interactions: mutualism, commensalism, parasitism, predation, competition, Lotka-Volterra models, competitive exclusion, niche differentiation, and keystone species dynamics); ecosystem ecology (energy flow, Lindeman's 10% rule, ecological pyramids of energy, biomass, and numbers, primary and secondary productivity); biogeochemical cycles (carbon, nitrogen, phosphorus, and hydrological cycles); ecological succession (primary vs secondary succession, pioneer species, seral stages, and climax ecosystems); conservation biology, island biogeography (MacArthur-Wilson model), habitat fragmentation, biomagnification, and biodiversity of Brazilian biomes (Amazônia, Cerrado, Caatinga, Mata Atlântica, Pantanal, and Pampa).

Not published

Evolução e Sistemática

Mechanisms of microevolution and macroevolution; natural selection modes (directional, stabilizing, and disruptive selection); genetic drift (bottleneck effect and founder effect); gene flow, mutation rates, and non-random mating; quantitative population genetics and the Hardy-Weinberg equilibrium principle (allele and genotype frequency calculations, testing assumptions, and selection coefficients); speciation processes (allopatric, peripatric, parapatric, and sympatric speciation, reproductive isolation mechanisms); phylogenetic systematics and cladistics (monophyletic, paraphyletic, and polyphyletic groups, synapomorphies, symplesiomorphies, homoplasies, convergent evolution, and maximum parsimony tree reconstruction); molecular evolution, neutral theory, molecular clocks, and major evolutionary transitions in life history.

How to Pass the OBB Exam

What You Need to Know

  • Passing score: Rank-based national qualification cutoffs determined by Instituto Butantan
  • Assessment: Three sequential national elimination stages: Stage 1 (25 MCQs, 30-minute to 2-hour window), Stage 2 (30 MCQs, 30-minute to 2-hour window for Stage 1 qualifiers), and Stage 3 (25 true/false sentences, 30-minute to 2-hour window). This practice bank provides 100 comprehensive practice questions in English covering the entire OBB syllabus.
  • Time limit: 30-minute to 2-hour window per elimination stage
  • Exam fee: Free (Gratuito)

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

Frequently Asked Questions

What is the Olimpíada Brasileira de Biologia (OBB)?

The Olimpíada Brasileira de Biologia (OBB) is Brazil's premier annual biology competition for high school and 9th-year elementary students. Organized by the Instituto Butantan, it promotes excellence in biological sciences, awards national medals, enables direct Olympic university admissions (Vagas Olímpicas), and serves as the qualification gateway for Brazilian delegations to the International Biology Olympiad (IBO) and the Ibero-American Biology Olympiad (OIAB).

How is the OBB structured according to the 2026 Instituto Butantan regulation?

According to the 2026 regulation, the OBB consists of three national elimination stages: Stage 1 (Fase 1) features 25 multiple-choice questions in an online window of 30 to 90 minutes; Stage 2 (Fase 2) features 30 multiple-choice questions in an online window of 30 to 90 minutes for Stage 1 qualifiers; and Stage 3 (Fase 3) is the comprehensive national final exam. Top medalists from Stage 3 are subsequently invited to a separate international team training and selection phase (Capacitação e Seletiva IBO/OIAB).

Who is eligible to participate in the OBB?

Participation is open to students regularly enrolled in Brazilian public or private schools in the 1st, 2nd, 3rd, or 4th year of Ensino Médio (or technical high school) as well as students in the 9th year of Ensino Fundamental II, aged up to 19 years old, provided they have not previously enrolled in higher education.

What are Vagas Olímpicas and how do OBB medals help with university admission?

Vagas Olímpicas (Olympic Quotas) are dedicated university spots established by top Brazilian public universities such as USP (Universidade de São Paulo), UNICAMP (Universidade Estadual de Campinas), and UNESP (Universidade Estadual Paulista). Gold, silver, and bronze medalists in the OBB can apply for direct, tuition-free admission to undergraduate degree programs (such as Medicine, Biological Sciences, Biomedicine, and Biotechnology) based on their Olympic medal achievements, bypassing traditional vestibular entrance exams like FUVEST and COMVEST.

What language is the official OBB conducted in, and why is this practice bank in English?

The official OBB competition administered in Brazil is conducted in Portuguese. This practice bank is provided in English to prepare students both for advanced domestic competition and for international biology competitions (IBO and OIAB) where English is the primary working language, while retaining essential Brazilian biological terminology and biome-specific contexts.

What is the fee to register and participate in the OBB?

Participation in the OBB is 100% free of charge (Gratuito) for all eligible students and schools throughout Brazil. Registration is completed directly by schools and teachers on the official Instituto Butantan platform.