100+ Free Bac STL Practice Questions

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When enumerating bacteria by plating, why are only plates showing roughly 30 to 300 colonies usually counted?

It is a legal limit set by the exam board

Plates with many colonies grow faster

Colonies below 30 are always contaminants

Fewer than 30 is statistically unreliable and more than 300 is hard to count accurately

to track

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2026 Statistics

Key Facts: Bac STL Exam

France's laboratory-science bac: two coefficient-16 Terminale specialties (BBB or SPCL, plus Physique-Chimie et Mathematiques), each combining a 3-hour written exam with a 3-hour practical, with 10/20 needed to pass.

Sample Bac STL Practice Questions

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

1In the French Baccalauréat Technologique STL, what does the abbreviation 'STL' stand for?

A.Sciences et Technologies du Laboratoire industriel

B.Sciences, Techniques et Logistique

C.Sciences et Travaux de Laboratoire

D.Sciences et Technologies de Laboratoire

Explanation: STL stands for 'Sciences et Technologies de Laboratoire', a technological track of the French baccalauréat centred on experimental laboratory science. It is administered by the Ministère de l'Éducation nationale.

2In Terminale STL, a student chooses between two specialty pathways for the major laboratory-science specialty. Which pair is correct?

A.Biochimie-Biologie-Biotechnologies (BBB) or Sciences Physiques et Chimiques en Laboratoire (SPCL)

B.Biotechnologies or Génie Industriel

C.Physique Appliquée or Chimie Analytique

D.Microbiologie or Pharmacologie

Explanation: In Terminale STL the major specialty is either Biochimie-Biologie-Biotechnologies (BBB) or Sciences Physiques et Chimiques en Laboratoire (SPCL). Both carry coefficient 16 and combine written and practical assessment.

3What coefficient is assigned to the Terminale STL major specialty (BBB or SPCL) final examination?

A.8

B.12

C.16

D.4

Explanation: The major STL specialty (BBB or SPCL) carries coefficient 16, the same as the Physique-Chimie et Mathématiques specialty. These two coefficient-16 specialties dominate the final score.

4The Terminale STL major specialty exam (BBB or SPCL) is assessed in two parts. What are they?

A.A multiple-choice test and an oral defence

B.A 4-hour essay and a portfolio

C.A continuous-assessment grade only

D.A 3-hour written exam and a 3-hour practical (ECE) exam

Explanation: The major STL specialty is assessed by a 3-hour written exam plus a 3-hour practical laboratory exam (épreuve pratique / ECE). This dual format reflects the experimental focus of the STL series.

5In glycolysis, glucose (a 6-carbon sugar) is converted into which 3-carbon end products?

A.Two molecules of pyruvate

B.Two molecules of lactate only

C.One molecule of acetyl-CoA

D.Two molecules of citrate

Explanation: Glycolysis splits one glucose molecule into two molecules of pyruvate (each 3 carbons), with a net gain of 2 ATP and 2 NADH. Pyruvate's fate then depends on whether the cell respires or ferments.

6During aerobic cellular respiration, where does the electron transport chain (oxidative phosphorylation) take place?

A.In the cytosol

B.In the nucleus

C.On the rough endoplasmic reticulum

D.On the inner mitochondrial membrane

Explanation: The electron transport chain and ATP synthase are embedded in the inner mitochondrial membrane (cristae). The proton gradient created across this membrane drives chemiosmotic ATP synthesis.

7Alcoholic fermentation, used in baking and brewing, converts pyruvate into which two products?

A.Lactate and water

B.Acetyl-CoA and NADH

C.Glucose and oxygen

D.Ethanol and carbon dioxide

Explanation: In alcoholic fermentation, yeast convert pyruvate into ethanol and CO2 while regenerating NAD+ so that glycolysis can continue. This anaerobic pathway yields only the 2 ATP from glycolysis.

8An enzyme increases the rate of a biochemical reaction by which mechanism?

A.By raising the activation energy of the reaction

B.By increasing the temperature of the medium

C.By shifting the equilibrium toward the products

D.By lowering the activation energy of the reaction

Explanation: Enzymes are biological catalysts that lower the activation energy (Ea) of a reaction, allowing it to proceed faster at body temperature. They do not change the position of equilibrium, only the rate at which it is reached.

9In the Michaelis-Menten model, what does the parameter Km represent?

A.The maximum reaction velocity

B.The total enzyme concentration

C.The turnover number of the enzyme

D.The substrate concentration giving half the maximum velocity

Explanation: Km (the Michaelis constant) is the substrate concentration at which the reaction velocity equals Vmax/2. A low Km indicates high apparent affinity of the enzyme for its substrate.

10A competitive inhibitor of an enzyme typically has which effect on the kinetic parameters?

A.Increases apparent Km, Vmax unchanged

B.Decreases Vmax, Km unchanged

C.Decreases both Km and Vmax

D.Increases Vmax, Km unchanged

Explanation: A competitive inhibitor binds the active site and competes with substrate, so more substrate is needed to reach a given rate: apparent Km rises while Vmax stays the same because saturation can still be reached.

About the Bac STL Exam

The Baccalaureat Technologique STL is the French laboratory-science technological track of the baccalaureat, awarded by the Ministere de l'Education nationale. In Terminale, students follow a major specialty, either Biochimie-Biologie-Biotechnologies (BBB) or Sciences Physiques et Chimiques en Laboratoire (SPCL), assessed by a 3-hour written exam and a 3-hour practical (ECE) at coefficient 16, plus a Physique-Chimie et Mathematiques specialty also at coefficient 16. Common-core exams include Philosophie (coefficient 4) and the anticipated Francais written and oral (coefficient 5 each), with a Grand oral at coefficient 14 (12 from the 2027 session). BBB covers enzymes and metabolism, immunity, DNA technologies (PCR, ELISA, electrophoresis), microbiology and bioreactors, while SPCL covers chimie et developpement durable, ondes, and systemes et procedes. The diploma gives access to higher education such as BTS, BUT, CPGE TB/TPC and university science degrees.

Questions

100 scored questions

Time Limit

Specialty: 3h written + 3h practical (ECE); PCM: 3h; Philosophie: 4h

Passing Score

10/20 overall to pass; 8-10/20 resit orals; mentions at 12, 14, 16 out of 20

Exam Fee

Free for candidates enrolled in French public lycees (national diploma, no exam fee) (Ministere de l'Education nationale (French academies))

Bac STL Exam Content Outline

16%

Biochemistry, enzymes and metabolism

Glycolysis, respiration, fermentation, enzyme kinetics (Michaelis-Menten), proteins, lipids and carbohydrates.

16%

Immunology and molecular biology

Self/non-self, innate and adaptive immunity, antibodies, DNA structure and replication, transcription, genetic code, PCR.

14%

Microbiology and bioprocess

Aseptic technique, Gram stain, growth curves, enumeration, antibiograms, sterilisation, selective media and bioreactors.

12%

Laboratory techniques (biotech)

ELISA, electrophoresis, SDS-PAGE, Western blot, chromatography, micropipetting and spectrophotometric quantification.

14%

Chemistry and sustainable development (SPCL)

Acid-base and redox, titration, conductimetry, pH, precipitation, green chemistry, synthesis, yield and purification.

12%

Waves and spectroscopy (SPCL)

Wave relations, refraction, diffraction, IR/UV-visible and emission spectroscopy, photon energy and colour.

Systems, processes and instrumentation

Feedback control, sensors, Ohm's law, signal acquisition (ADC), heat exchangers and pH electrodes.

Measurement, uncertainty and exam structure

Type A/B uncertainty, trueness vs precision, significant figures, lab safety, coefficients and grading.

How to Pass the Bac STL Exam

What You Need to Know

Passing score: 10/20 overall to pass; 8-10/20 resit orals; mentions at 12, 14, 16 out of 20
Exam length: 100 questions
Time limit: Specialty: 3h written + 3h practical (ECE); PCM: 3h; Philosophie: 4h
Exam fee: Free for candidates enrolled in French public lycees (national diploma, no exam fee)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

Bac STL Study Tips from Top Performers

1Master the core formulas: Beer-Lambert (A = e x l x c), the wave relation v = f x lambda, and the bacterial growth model N = N0 x 2 raised to the number of generations.

2For BBB, drill the lab techniques (ELISA calibration curves, electrophoresis, PCR cycles, enzyme kinetics) since the practical ECE rewards protocol understanding.

3For SPCL, practise titration and dilution calculations and learn to read IR and UV-visible spectra to identify functional groups and coloured species.

4Always report measurements with their uncertainty and correct significant figures, and distinguish Type A from Type B evaluations.

5Practise interpreting documents and writing a structured synthesis, as the written specialty paper is built around document study and argued reasoning.

6Link your projet technologique to the Grand oral so you can present a concrete experiment with confidence.

Frequently Asked Questions

What are the two specialty pathways in Terminale STL?

Students follow either Biochimie-Biologie-Biotechnologies (BBB), centred on living systems, biochemistry, microbiology and lab techniques, or Sciences Physiques et Chimiques en Laboratoire (SPCL), centred on chemistry, waves, instrumentation and processes. Both carry coefficient 16.

How is the STL specialty exam structured?

The major specialty (BBB or SPCL) is assessed by a 3-hour written exam (document study plus a synthesis question) and a separate 3-hour practical laboratory exam (ECE). There is no multiple-choice component in the real exam.

What coefficient do the STL specialties carry?

The major laboratory-science specialty (BBB or SPCL) and the Physique-Chimie et Mathematiques specialty each carry coefficient 16, making them the two heaviest-weighted exams of the STL baccalaureat.

What score is needed to pass the baccalaureat?

An overall weighted average of 10/20 awards the baccalaureat. Candidates between 8 and 10 sit oral resit exams (rattrapage). Distinctions are awarded at 12 (assez bien), 14 (bien) and 16 (tres bien).

Is there a fee to sit the Bac STL?

No. The baccalaureat is a free national diploma for candidates enrolled in French public lycees; there is no exam registration fee.

What can you study after a Bac STL?

The Bac STL gives access to higher education including BTS and BUT in laboratory, biology and chemistry fields, the CPGE TB and TPC preparatory classes, and university science degrees.