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Free Practice Questions for Lebanese Baccalaureate — Life Sciences (LS)

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Key Facts: Lebanese Baccalaureate — Life Sciences (LS) Exam

10/20

Minimum Passing Average

MEHE Examination Regulations

Coeff. 5

Biology Coefficient (Highest in LS Stream)

Official CRDP Curriculum Structure

40,000 LBP

Nominal Registration Fee

Ministry of Education & Higher Education

Grade 12

Final Secondary Year (Terminale SV/LS)

Lebanese Educational System Structure

3 Languages

Arabic, French, or English Tracks

MEHE Examination Administration

The Lebanese Baccalaureate Life Sciences (LS/SV) is Lebanon's national exit examination for pre-medical and health science secondary students. Official exams are paper-based constructed-response sessions administered by MEHE in Arabic, French, or English. This 108-question bank is an English-language MCQ study adaptation created by OpenExamPrep to reinforce high-yield concepts across the official CRDP curriculum.

Sample Lebanese Baccalaureate — Life Sciences (LS) Practice Questions

Try these sample questions to review concepts for the Lebanese Baccalaureate — Life Sciences (LS) exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 108+ question experience with AI tutoring.

1What is the primary ionic mechanism responsible for establishing and maintaining the resting membrane potential of approximately -70 mV in an unexcited neuron?
A.High membrane permeability to potassium ions leaking outward and active transport by Na+/K+ ATPase pumps
B.Continuous passive diffusion of sodium ions into the cell through non-gated channels
C.Active influx of calcium ions coupled with rapid passive efflux of chloride ions
D.Equal permeability to all extracellular cations accompanied by intracellular accumulation of sulfate ions
Explanation: The resting membrane potential is predominantly determined by the high permeability of the resting neuronal membrane to potassium ions through open K+ leak channels, allowing K+ to diffuse down its chemical gradient out of the cell. The Na+/K+ ATPase electrogenic pump actively moves 3 Na+ out for every 2 K+ pumped in, maintaining the steep concentration gradients and keeping the interior negative relative to the exterior.
2During the depolarizing phase of a neuronal action potential, which molecular event directly accounts for the rapid reversal of membrane polarity toward +30 mV?
A.Inward flow of chloride ions through ligand-gated ion channels
B.Voltage-dependent opening of activation gates in voltage-gated sodium channels causing Na+ influx
C.Rapid efflux of potassium ions through delayed rectifier channels
D.Active extrusion of calcium ions by electrogenic secondary active transporters
Explanation: When an initial stimulus depolarizes the axon membrane to its excitation threshold (around -55 mV), voltage-gated sodium channels rapidly open their activation gates. Driven by both concentration and electrical gradients, sodium ions rush into the axoplasm, causing an explosive regenerative inward current that drives the membrane potential toward the sodium equilibrium potential (+30 mV).
3What causes the transient hyperpolarization (undershoot phase) observed at the conclusion of a neuronal action potential before returning to the resting potential?
A.Complete closure of all potassium channels while the sodium-potassium pump ceases function
B.Rapid influx of extracellular magnesium ions through transient receptor potential channels
C.Delayed closure of voltage-gated potassium channels allowing continuous K+ efflux toward its equilibrium potential
D.Sustained opening of voltage-gated sodium channels operating in reverse mode
Explanation: Voltage-gated potassium channels close relatively slowly in response to membrane repolarization. Because these channels remain open for several milliseconds after resting voltage is reached, potassium permeability remains temporarily higher than at rest, driving the membrane potential closer to the potassium equilibrium potential (-90 mV) before settling back to -70 mV.
4Why is it physiologically impossible to generate a second action potential during the absolute refractory period of an axon, regardless of stimulus strength?
A.The potassium equilibrium potential shifts temporarily to a positive value
B.All neurotransmitter vesicles in the presynaptic terminal have been depleted
C.The myelin sheath temporarily increases axial resistance along the internodal segments
D.Voltage-gated sodium channels are in an inactivated state with closed inactivation gates
Explanation: During the absolute refractory period, voltage-gated Na+ channels are either already open or their inactivation gates (h-gates) are closed. These channels cannot transition back to the closed-activatable state until the membrane repolarizes sufficiently, meaning no new inward sodium current can be elicited no matter how intense the depolarizing stimulus is.
5How does an isolated sensory nerve fiber encode an increase in stimulus intensity according to the all-or-none law?
A.By increasing the frequency of generated action potentials of constant amplitude
B.By progressively increasing the amplitude and duration of individual action potentials
C.By shifting conduction from saltatory transmission to continuous electrotonic spread
D.By converting action potentials into graded local hyperpolarizations
Explanation: According to the all-or-none law, once the threshold of excitation is reached, a single nerve fiber produces an action potential of fixed amplitude and waveform. Greater stimulus intensity is therefore encoded by an increased discharge frequency of action potentials (frequency modulation), rather than changes in spike height.
6What structural and functional feature explains why myelinated nerve fibers conduct nerve impulses significantly faster than unmyelinated fibers of equivalent diameter?
A.Action potentials are continuously regenerated at every micrometer of the axolemma
B.High membrane resistance and low capacitance at internodes restrict depolarization to the nodes of Ranvier
C.Myelin contains active ATP-driven pumps that propel sodium ions longitudinally
D.Voltage-gated calcium channels replace sodium channels across the entire length of the sheath
Explanation: Myelin acts as an electrical insulator that markedly increases trans-membrane resistance and decreases capacitance along internodes. Local electrotonic currents spread rapidly with minimal decay through the axoplasm, triggering regenerative action potentials exclusively at the unmyelinated nodes of Ranvier where voltage-gated Na+ channels are densely clustered, a process called saltatory conduction.
7At a chemical synapse, which critical event directly links the arrival of a presynaptic action potential to the exocytosis of neurotransmitter vesicles into the synaptic cleft?
A.Efflux of potassium ions through delayed rectifier channels
B.Direct mechanical opening of postsynaptic acetylcholine-gated channels by local currents
C.Opening of voltage-gated calcium channels leading to Ca2+ influx into the presynaptic terminal
D.Rapid breakdown of cyclic AMP by presynaptic phosphodiesterases
Explanation: Depolarization of the presynaptic terminal membrane triggers the opening of voltage-gated calcium channels. Because the extracellular calcium concentration is roughly 10,000 times higher than free intracellular levels, Ca2+ rushes into the terminal, binding to synaptotagmin and activating the SNARE complex to fuse neurotransmitter vesicles with the presynaptic membrane.
8Which ionic mechanism explains how the binding of GABA to its ionotropic GABAA receptors produces an inhibitory postsynaptic potential (IPSP)?
A.Direct activation of calcium pumps that decreases extracellular calcium levels
B.Opening of voltage-gated sodium channels that depolarizes the membrane toward threshold
C.Blockade of leak potassium channels that prevents potassium from exiting the cell
D.Opening of receptor-associated chloride channels causing Cl- influx that hyperpolarizes the postsynaptic membrane
Explanation: GABAA receptors are ligand-gated ion channels selective for chloride ions. When GABA binds, the channel pore opens, allowing Cl- to enter the postsynaptic neuron down its concentration gradient, which increases the negativity of the interior (hyperpolarization) and moves the membrane potential further away from the firing threshold.
9A postsynaptic motor neuron receives simultaneous subthreshold EPSPs from three distinct excitatory presynaptic terminals, resulting in the generation of an action potential at the axon hillock. Which phenomenon does this describe?
A.Spatial summation
B.Temporal summation
C.Post-tetanic potentiation
D.Presynaptic lateral inhibition
Explanation: Spatial summation occurs when multiple distinct presynaptic inputs release neurotransmitter onto different locations of the postsynaptic neuron at the same time. The individual local graded potentials propagate electrotonically to the axon hillock, where their algebraic sum reaches or exceeds threshold to fire an action potential.
10During the human patellar (knee-jerk) reflex, what is the neuronal circuit mechanism that ensures the relaxation of the antagonist hamstring muscle while the agonist quadriceps contracts?
A.Sensory Ia afferent fibers directly synapse on antagonist motor neurons to hyperpolarize them
B.Sensory Ia afferent fibers bifurcate in the spinal cord and activate inhibitory interneurons that synapse on antagonist motor neurons
C.Motor neurons to the quadriceps release inhibitory acetylcholine onto adjacent hamstring muscle fibers
D.Renshaw cells in the motor cortex inhibit descending pyramidal tracts to both muscle groups
Explanation: The myotatic reflex includes reciprocal innervation: primary sensory Ia afferent fibers from muscle spindles directly excite alpha motor neurons of the stretched agonist muscle (monosynaptic pathway) while simultaneously synapsing on inhibitory interneurons (Ia interneurons) in the spinal cord gray matter. These interneurons release glycine or GABA to inhibit the motor neurons supplying the antagonist muscle, causing it to relax.

About the Lebanese Baccalaureate — Life Sciences (LS) Exam

The Lebanese Baccalaureate — Life Sciences (LS) stream (شهادة الثانوية العامة - فرع علوم الحياة, often referred to in French as Baccalauréat Sciences de la Vie or SV) is Lebanon's premier secondary school-leaving credential for students preparing for university studies in medicine, pharmacy, dentistry, biological sciences, nursing, and related health disciplines. Administered annually by the Ministry of Education and Higher Education (MEHE) in coordination with the Center for Educational Research and Development (CRDP / CERD), the official examination is administered in Arabic, French, or English depending on the school's instructional language. Official exams consist of demanding, constructed-response written papers, experimental data evaluations, and multi-step derivations sat over several days. This 108-question practice bank is an independent English-language multiple-choice question (MCQ) study adaptation developed by OpenExamPrep to help students reinforce foundational concepts across neurophysiology, immunology, molecular genetics, organic and physical chemistry, classical mechanics, electromagnetism, calculus, probability, and bioethics.

Exam sponsor: Ministry of Education and Higher Education (MEHE / وزارة التربية والتعليم العالي) & Center for Educational Research and Development (CRDP / CERD). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

The official Lebanese Baccalaureate LS stream consists of written examinations administered nationwide over five examination days. Candidates sit subject papers in Life Sciences, Chemistry, Physics, Mathematics, Philosophy and Civilizations, Arabic Language and Literature, Foreign Language and Literature, History, Geography and Civics. Each paper is marked out of 20 and weighted by an official coefficient, giving maximum marks of 100 for Life Sciences, 80 each for Chemistry, Physics and Mathematics, 50 for Arabic, 40 for the foreign language, 40 for Philosophy, and 30 each for History, Geography and Civics, for a total of 560 points. Official papers are sat in Arabic, French or English; this bank is an English-language MCQ study adaptation by OpenExamPrep.

Time Limit

Written papers are sat over five examination days according to the annual MEHE timetable. In the 2026 session the Life Sciences papers included Life Sciences (3 hours), Chemistry (2 hours), Mathematics (2 hours), Philosophy and Civilizations (2 hours), Arabic Language and Literature (2.5 hours), Foreign Language and Literature (2.5 hours), and Geography, History and Civics (1 hour each).

Passing Score

An overall weighted average of at least 10 out of 20, that is at least 280 of the 560 coefficient-weighted points of the Life Sciences stream.

Exam / Certification Fees

40,000 LBP (nominal public candidate registration fee under MEHE)

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

18% of official marks (100 / 560)

Biology: Neurophysiology, Immunology & Genetics

Electrophysiological properties of neurons (resting potential, action potential, synapse neurotransmission), immunology mechanisms (HLA antigens, humoral and cell-mediated responses, HIV cycle), and molecular genetics (Mendelian crosses, chromosomal mutations, DNA replication, gene expression).

14% of official marks (80 / 560)

Chemistry: Kinetics, Equilibria & Organic Chemistry

Rates of chemical reactions, collision theory, Le Chatelier's equilibrium shifts, acid-base equilibrium calculations, pH titrations, buffer systems, and organic functional groups (alcohols, carbonyls, esters, saponification, amino acids, and proteins).

14% of official marks (80 / 560)

Physics: Mechanics, Oscillations & Electromagnetism

Newtonian dynamics, work, kinetic and potential energy conservation, harmonic oscillators, resonance phenomena, electromagnetic induction (Faraday's and Lenz's laws), AC circuits, and wave-particle duality.

14% of official marks (80 / 560)

Mathematics: Calculus & Discrete Probability

Limits, derivatives, curve analysis, exponential and logarithmic functions, definite integration, area under curves, conditional probability, independent events, and binomial distributions.

23% of official marks (130 / 560)

Philosophy & Bioethics

Ethical considerations in modern biotechnology (genetic editing, human reproductive cloning, clinical trials), the scientific method in life sciences (Claude Bernard's experimental approach, falsificationism), and philosophical textual reasoning.

16% of official marks (90 / 560)

History, Geography & Civics

Three one-hour papers examined in the Life Sciences stream: modern and contemporary Lebanese and Arab history, the physical and human geography of Lebanon including environment and water resources, and civics (the Constitution, state institutions, citizenship, rights and duties).

Preparing for the Lebanese Baccalaureate — Life Sciences (LS) Exam

What You Need to Know

  • Passing score: An overall weighted average of at least 10 out of 20, that is at least 280 of the 560 coefficient-weighted points of the Life Sciences stream.
  • Assessment: The official Lebanese Baccalaureate LS stream consists of written examinations administered nationwide over five examination days. Candidates sit subject papers in Life Sciences, Chemistry, Physics, Mathematics, Philosophy and Civilizations, Arabic Language and Literature, Foreign Language and Literature, History, Geography and Civics. Each paper is marked out of 20 and weighted by an official coefficient, giving maximum marks of 100 for Life Sciences, 80 each for Chemistry, Physics and Mathematics, 50 for Arabic, 40 for the foreign language, 40 for Philosophy, and 30 each for History, Geography and Civics, for a total of 560 points. Official papers are sat in Arabic, French or English; this bank is an English-language MCQ study adaptation by OpenExamPrep.
  • Time limit: Written papers are sat over five examination days according to the annual MEHE timetable. In the 2026 session the Life Sciences papers included Life Sciences (3 hours), Chemistry (2 hours), Mathematics (2 hours), Philosophy and Civilizations (2 hours), Arabic Language and Literature (2.5 hours), Foreign Language and Literature (2.5 hours), and Geography, History and Civics (1 hour each).
  • Exam / certification fees: 40,000 LBP (nominal public candidate registration fee under MEHE) Official sources

Using Our Practice Resources

  • Work through all 108 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

Lebanese Baccalaureate — Life Sciences (LS): Suggested Study Strategy

1Master biological document analysis techniques: practice converting experimental data into hypothesis statements, operational observations, and logical deductions.
2Practice quantitative chemical equilibrium problems regularly, paying close attention to stoichiometric ratios, ICE tables, and logarithmic pH calculations.
3Verify units and vector signs carefully when solving mechanics and electromagnetic induction problems, particularly Lenz's law polarities.
4Review natural logarithm and exponential function derivatives and asymptotic behaviors to ensure rapid solving during calculus sections.
5Structure bioethics arguments with clear distinctions between utilitarian benefits and deontological principles regarding human dignity and genome editing.

Frequently Asked Questions

What is the Lebanese Baccalaureate Life Sciences (LS) stream?

The Lebanese Baccalaureate Life Sciences (LS) stream (فرع علوم الحياة / Sciences de la Vie) is the Grade 12 national secondary credential administered by the Ministry of Education and Higher Education (MEHE). It is the standard prerequisite for university admission to faculties of medicine, pharmacy, biology, biochemistry, dentistry, and allied healthcare disciplines in Lebanon and abroad.

In what languages is the official Lebanese Baccalaureate administered?

Official Lebanese Baccalaureate examinations are administered nationally in Arabic, French, or English. Students in French-track or English-track schools sit their scientific papers (Biology, Chemistry, Physics, Mathematics) in French or English respectively, while Arabic Language and Humanities subjects are administered in Arabic (with General Philosophy offered in French or English for foreign-language tracks). This OpenExamPrep question bank is an English-language MCQ adaptation designed for conceptual study and self-testing.

Are official Lebanese Baccalaureate exams multiple-choice?

No. The official Lebanese Baccalaureate examinations consist entirely of written, constructed-response papers requiring comprehensive derivations, experimental hypothesis testing, document analysis, scientific essays, and handwritten calculations. This practice bank adapts the core curriculum into a 108-question multiple-choice format to support fast diagnostic review and conceptual mastery.

What is the passing score for the Lebanese Baccalaureate?

A candidate must achieve an overall weighted average of at least 10 out of 20, which corresponds to at least 280 of the 560 coefficient-weighted points of the Life Sciences stream, to be awarded the Baccalaureate diploma. Honors mentions (Mention) are awarded for higher averages: Fairly Good (Assez Bien, 12–13.99/20), Good (Bien, 14–15.99/20), and Very Good (Très Bien, 16/20 and above).

What subjects carry the highest weight in the Life Sciences track?

In the Grade 12 Life Sciences stream, Life Sciences (Biology) carries a coefficient of 5, while Chemistry, Physics, and Mathematics each carry a coefficient of 4. These four core scientific disciplines together represent the vast majority of total exam points.

How should students use this 108-question practice bank?

Students should use these questions alongside official CRDP textbooks and past national exam sessions. Each question includes complete rationales explaining the underlying biological, chemical, or physical mechanism, as well as specific explanations for why each distractor is incorrect.

Were the official Lebanese Baccalaureate examinations held in 2026?

For the 2025-2026 school year the Council of Ministers exempted regular school students from the official examinations and issued an official certificate of success (ifadat najah) to candidates whose school average reached at least 9.5/20 on 1 March 2026. A single exceptional written session was held for free candidates, students who fell below that average and voluntary candidates, and it ran over five examination days: 26, 27, 29 and 31 August and 1 September 2026.