Free Practice Questions for Basque PAU Biology

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Key Facts: Basque PAU Biology Exam

90 Minutes

Exam time duration

UPV/EHU PAU Commission

EUR 86.33

Ordinary registration fee

UPV/EHU 2026 PAU

0–10 Scale

Grading scale for Bachillerato and PAU exams

Spanish Ministry of Education & UPV/EHU

5 Core Blocks

Biomolecules, Cell Biology, Metabolism, Molecular Genetics, Microbiology & Immunology

2º Bachillerato Biology Syllabus

100 Questions

Practice bank size in OpenExamPrep

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Basque Country PAU Biology (UPV/EHU 2026) is a 90-minute university entrance exam assessing 2º Bachillerato syllabus domains.

Sample Basque PAU Biology Practice Questions

Try these sample questions to review concepts for the Basque PAU Biology exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Why does liquid water have an exceptionally high specific heat capacity compared to other small covalent molecules?

A.Extensive intermolecular hydrogen bonding absorbs thermal energy before increasing kinetic movement.

B.Covalent bonds within water molecules continuously break and reform at room temperature.

C.Water molecules form ionic complexes that retain thermal kinetic energy efficiently.

D.High molecular mass allows water to store vast amounts of rotational kinetic energy.

Explanation: Water possesses a high specific heat capacity (4.184 J/g°C) because a significant portion of absorbed heat energy goes into disrupting hydrogen bonds between adjacent molecules rather than increasing their translation kinetic speed. This property prevents sudden temperature fluctuations in biological fluids and organismal tissues, stabilizing metabolic environments.

2Which physical property of water enables continuous sap transport against gravity in xylem vessels of tall plants?

A.Low surface tension and high compressibility

B.High cohesion and adhesion combined with high tensile strength

C.Maximal density at 4 degrees Celsius and low viscosity

D.High dielectric constant and low specific heat capacity

Explanation: Cohesion (hydrogen bonding between adjacent water molecules) and adhesion (hydrogen bonding between water and xylem cell wall components like cellulose) allow water to form a continuous column under tension. Transpiration pull pulls this cohesive column upward without breaking.

3What happens to a plant cell when it is placed into a hypertonic salt solution?

A.Water enters the vacuole causing the cell to burst via osmotic lysis.

B.Sodium ions enter the cell via simple diffusion until turgor pressure stabilizes.

C.Water leaves the central vacuole causing the plasma membrane to detach from the cell wall (plasmolysis).

D.Solute equilibrium is maintained with no net movement of water across the membrane.

Explanation: In a hypertonic environment, the solute concentration outside the cell exceeds that in the cytoplasm. Osmotic pressure drives net water flow out of the central vacuole and cytoplasm, shrinking the protoplast and pulling the plasma membrane away from the rigid cell wall—a process termed plasmolysis.

4Which functional group distinction differentiates an aldose monosaccharide like D-glucose from a ketose like D-fructose?

A.An aldose cannot form D and L enantiomeric isomers, whereas a ketose can.

B.An aldose has carboxylic acid groups, whereas a ketose contains ester linkages.

C.An aldose forms ring structures with five atoms, whereas a ketose forms rings with seven atoms.

D.An aldose contains a carbonyl group at carbon-1 (aldehyde), whereas a ketose contains a carbonyl at carbon-2 (ketone).

Explanation: Aldoses possess an aldehyde functional group (-CHO) located at the terminal carbon (C-1). Ketoses possess a ketone functional group (C=O) located at an internal carbon atom, typically carbon-2 (C-2). Both glucose and fructose are hexoses with the chemical formula C6H12O6.

5Why is sucrose considered a non-reducing disaccharide, unlike maltose and lactose?

A.The glycosidic bond involves the anomeric carbons of both glucose (alpha-1) and fructose (beta-2), leaving no free anomeric hydroxyl group.

B.Sucrose lacks hydroxyl groups capable of participating in oxidation-reduction reactions.

C.Sucrose is composed exclusively of beta-D-galactose monomers joined by beta-1,4-bonds.

D.Sucrose spontaneously hydrolyzes into free carboxylic acids in aqueous solution.

Explanation: A reducing sugar requires a free anomeric carbon (C-1 in aldoses, C-2 in ketoses) capable of opening into an open-chain aldehyde or ketone to reduce Benedict's or Fehling's reagents. In sucrose, the O-glycosidic bond links C-1 of alpha-D-glucose directly to C-2 of beta-D-fructose, tying up both anomeric carbons.

6What structural difference explains why humans can digest starch but cannot digest structural cellulose?

A.Starch is composed of D-glucose monomers, whereas cellulose is composed of L-galactose monomers.

B.Starch consists of alpha-1,4 and alpha-1,6 glycosidic bonds, whereas cellulose consists of unbranched beta-1,4 glycosidic bonds.

C.Starch contains nitrogenous amino groups, whereas cellulose contains phosphate ester linkages.

D.Starch is a linear protein complex, whereas cellulose is a branched lipid polymer.

Explanation: Human digestive enzymes like alpha-amylase specifically recognize and hydrolyze alpha-1,4 glycosidic bonds found in amylose and amylopectin (starch). Cellulose consists of linear chains of beta-D-glucose joined by beta-1,4 glycosidic bonds, which human enzymes cannot cleavage due to substrate specificity.

7Which heteropolysaccharide serves as a major structural component of animal extracellular matrix and synovial fluid?

A.Amylopectin

B.Glycogen

C.Hyaluronic acid

D.Inulin

Explanation: Hyaluronic acid (hyaluronan) is a non-sulfated glycosaminoglycan (heteropolysaccharide) composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine. It forms high-viscosity gels in animal extracellular matrices, cartilage, and synovial fluid.

8How does the introduction of cis double bonds into hydrocarbon chains affect the melting point of fatty acids?

A.It eliminates hydrophobic interactions, rendering the fatty acid fully water-soluble.

B.It increases molecular linearity, promoting tight hydrophobic stacking and raising the melting point.

C.It enables ionic bonding between chains, converting liquid oils into solid crystalline fats.

D.It introduces kinks that disrupt van der Waals packing, lowering the melting point.

Explanation: Naturally occurring unsaturated fatty acids feature cis double bonds, which introduce fixed 30-degree bends ('kinks') in the hydrocarbon acyl chain. These kinks hinder compact parallel packing of adjacent molecules, weakening intermolecular van der Waals forces and lowering the melting point.

9Which structural feature grants glycerophospholipids their amphipathic property in biological membranes?

A.A hydrophilic polar head group (phosphate + alcohol) attached to a hydrophobic backbone of two fatty acyl chains

B.Three saturated fatty acid chains attached to a polar spherical carbohydrate ring

C.A steroid nucleus esterified to four hydrophilic polypeptide subunits

D.A single non-polar hydrocarbon chain attached to a polar peptide bond

Explanation: Glycerophospholipids possess a glycerol molecule esterified to two non-polar, hydrophobic fatty acid tails and one polar, hydrophilic phosphate group bound to an amino alcohol (like choline or ethanolamine). This amphipathic dual polarity drives spontaneous lipid bilayer self-assembly in aqueous solutions.

10Which parent molecule serves as the biochemical precursor for steroid hormones, vitamin D, and bile salts in animals?

A.Sphingomyelin

B.Cholesterol

C.Triacylglycerol

D.Phosphatidylcholine

Explanation: Cholesterol is an essential amphipathic sterol containing a fused four-ring steroid nucleus (cyclopentanoperhydrophenanthrene). In animal biochemistry, cholesterol is the direct biosynthetic precursor for steroid hormones (cortisol, aldosterone, estrogen, testosterone), vitamin D3, and bile acids.

About the Basque PAU Biology Exam

The Basque Country PAU Biology examination (Unibertsitaterako Sarbide Proba, UPV/EHU 2026) is the official standardized assessment for 2º Bachillerato students seeking university entry in the Basque Country (Euskadi). The exam assesses student mastery across five key biological domains: Biomolecules & Biochemistry, Cell Biology & Division, Metabolism & Cell Energetics, Molecular Genetics & Inheritance, and Microbiology & Immunology. This practice bank provides 100 high-quality questions with comprehensive explanations for all options.

Exam sponsor: PAU Organising Commission of the Basque Country / UPV/EHU. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Written 90-minute standardized exam. Local practice items are an English-language MCQ study adaptation of the official open/semi-constructed Basque Country PAU paper, not an official translation or format simulation.

Time Limit

90 minutes (1.5 hours)

Passing Score

Marked on a 0–10 scale. Minimum 4.0 required in Access Phase to combine with Bachillerato GPA (60% Bachillerato + 40% PAU >= 5.0 to pass).

Exam / Certification Fees

EUR 86.33 ordinary registration fee (UPV/EHU 2026 PAU)

Exam sponsor website

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

Official sources

UPV/EHU - Evaluación para el Acceso a la Universidad (PAU)

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.

20%

Biomolecules & Biochemistry

Chemical composition of living matter, bioelements, water, inorganic salts, carbohydrates, lipids, proteins, enzymes, and nucleic acids.

20%

Cell Biology & Division

Cell structure and function, plasma membrane and transport, endomembrane system, cell organelles, cytoskeleton, cell cycle, mitosis, and meiosis.

20%

Metabolism & Cell Energetics

Enzyme kinetics, catabolism (glycolysis, fermentation, Krebs cycle, oxidative phosphorylation), and anabolism (photosynthetic light and dark reactions, chemosynthesis).

20%

Molecular Genetics & Inheritance

DNA replication, transcription, RNA processing, genetic code, translation, regulation of gene expression, mutations, biotechnology, and mendelian inheritance.

20%

Microbiology & Immunology

Microorganisms (bacteria, viruses, fungi, protozoa), infectious diseases, innate and adaptive immunity, antibodies, cellular vs humoral responses, and immunization.

Preparing for the Basque PAU Biology Exam

What You Need to Know

Passing score: Marked on a 0–10 scale. Minimum 4.0 required in Access Phase to combine with Bachillerato GPA (60% Bachillerato + 40% PAU >= 5.0 to pass).
Assessment: Written 90-minute standardized exam. Local practice items are an English-language MCQ study adaptation of the official open/semi-constructed Basque Country PAU paper, not an official translation or format simulation.
Time limit: 90 minutes (1.5 hours)
Exam / certification fees: EUR 86.33 ordinary registration fee (UPV/EHU 2026 PAU) Official sources

Using Our Practice Resources

Work through all 100 available questions
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Track weak areas and revisit them
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Basque PAU Biology: Suggested Study Strategy

1Master biomolecule structures, chemical bonds (glycosidic, peptide, phosphodiester, ester), and physical properties of water.

2Understand cellular compartmentalization, membrane transport mechanisms, and organelle functions.

3Trace metabolic energy yields (ATP generation in glycolysis vs oxidative phosphorylation) and pathways' subcellular locations.

4Comprehend molecular genetics mechanisms: replication, transcription, translation, operon regulation, and Mendelian/non-Mendelian inheritance.

5Distinguish humoral vs cellular immunity, antibody structures (IgG, IgM, IgA, IgE, IgD), and viral vs bacterial replication.

Frequently Asked Questions

What is the registration fee for PAU Biology in the Basque Country?

The fee is EUR 86.33 for ordinary registration for the PAU at UPV/EHU for 2026.

How is the PAU Biology paper scored?

The paper is scored from 0 to 10 points. A minimum score of 4.0 points in the Access Phase is required to average with Bachillerato grades.

How long is the PAU Biology exam?

The examination duration is 90 minutes (1.5 hours).

What languages are available for the exam at UPV/EHU?

The official exam paper is provided in Basque (Euskara) and Spanish (Castellano).

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