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Exam Review

Key Facts: Extremadura PAU Biology Exam

90 Minutes

Official examination duration

UEx PAU Regulations

Min 4.0

Minimum Access Phase score required

UEx PAU Guidelines

5 Blocks

Biomolecules, Cytology, Metabolism, Genetics, Microbiology & Immunology

2º Bachillerato Biology Syllabus

EUR 78.26

Ordinary registration fee for PAU

UEx Fees

100

Practice questions available in this question bank

OpenExamPrep

Extremadura PAU Biology (UEx 2026) is a 90-minute university entrance exam assessing 2º Bachillerato Biology across 5 core subject blocks.

Sample Extremadura PAU Biology Practice Questions

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

1Which physicochemical property of water enables homeothermic organisms to maintain a stable body temperature through sweat evaporation?
A.High heat of vaporization caused by extensive intermolecular hydrogen bonding.
B.Low boiling point resulting from nonpolar covalent interactions.
C.High density in the solid state relative to the liquid state.
D.Low surface tension facilitating hydrophobic solute aggregation.
Explanation: Water possesses a high heat of vaporization (~540 cal/g) because substantial thermal energy must be absorbed to break intermolecular hydrogen bonds before water molecules can transition into the gas phase. Evaporation of sweat from skin removes this heat, cooling the body.
2What happens to human erythrocytes when they are placed into a hypertonic sodium chloride solution?
A.They absorb water via osmosis until undergoing osmotic lysis (hemolysis).
B.They lose water via osmosis to the external medium and undergo crenation (shriveling).
C.They take up sodium ions by simple diffusion, causing an increase in cell volume.
D.They remain morphologically unchanged because the cell membrane is completely impermeable to water.
Explanation: In a hypertonic solution, the solute concentration outside the red blood cell is higher than inside the cytoplasm. Water leaves the cell down its water potential gradient via osmosis, leading to cell shrinkage and crenation.
3Which hexose monosaccharide serves as the primary metabolic fuel for cellular respiration in human tissues?
A.D-Ribose
B.D-Galactose
C.D-Glucose
D.D-Fructose
Explanation: D-Glucose is an aldohexose that acts as the principal universal substrate for glycolysis and ATP generation in eukaryotic and prokaryotic cells.
4Which chemical feature distinguishes unsaturated fatty acids from saturated fatty acids?
A.The presence of branched hydrocarbon chains with aldehyde functional groups.
B.The presence of phosphate groups attached to the glycerol backbone.
C.The complete absence of carboxylic acid functional groups at the terminal carbon.
D.The presence of one or more carbon-carbon double bonds (C=C) in the hydrocarbon tail.
Explanation: Unsaturated fatty acids contain one (monounsaturated) or more (polyunsaturated) C=C double bonds in their hydrocarbon chains, creating kinks that lower their melting points compared to fully saturated fatty acids.
5What type of chemical covalent bond joins adjacent amino acid residues in a polypeptide chain?
A.Peptide bond (amide bond between alpha-carboxyl and alpha-amino groups).
B.Glycosidic bond between hydroxyl groups.
C.Phosphodiester bond between 3'-OH and 5'-phosphate groups.
D.Ester bond between fatty acid carboxyl and glycerol hydroxyl groups.
Explanation: Amino acids are polymerized via peptide bonds formed by a dehydration condensation reaction between the alpha-carboxyl group of one amino acid and the alpha-amino group of another.
6Which nitrogenous base is present exclusively in RNA and replaces thymine found in DNA?
A.Adenine
B.Uracil
C.Guanine
D.Cytosine
Explanation: Uracil is a pyrimidine base found in RNA that pairs with adenine. In DNA, thymine (5-methyluracil) takes the place of uracil.
7Why is water considered an excellent solvent for ionic compounds such as sodium chloride (NaCl)?
A.Because water molecules form nonpolar van der Waals interactions with uncharged solute ions.
B.Because water has a low dielectric constant that prevents ion separation.
C.Because water molecules are polar dipoles that form hydration shells around Na+ and Cl- ions.
D.Because water undergoes rapid covalent hydrolysis upon contact with inorganic salts.
Explanation: Water's high polarity and high dielectric constant allow its partial negative oxygen atoms to surround Na+ cations and partial positive hydrogen atoms to surround Cl- anions, forming hydration spheres that overcome ionic lattice attraction.
8Which physiological buffer system is primarily responsible for maintaining the pH of human blood plasma around 7.4?
A.Ammonium / Ammonia buffer system.
B.Acetate / Acetic acid buffer system.
C.Biphosphate / Monophosphate intracellular buffer system.
D.Carbonic acid / Bicarbonate buffer system (H2CO3 / HCO3-).
Explanation: The carbonic acid/bicarbonate system (H2CO3/HCO3-) buffers extracellular fluids like blood plasma. Excess H+ ions are neutralized by HCO3- to form H2CO3, which dissociates into CO2 and H2O for respiratory elimination.
9Which pair of monosaccharides forms sucrose through an alpha(1->2) O-glycosidic bond between their anomeric carbons?
A.alpha-D-Glucose and beta-D-Fructose.
B.alpha-D-Glucose and alpha-D-Glucose.
C.beta-D-Galactose and beta-D-Glucose.
D.alpha-D-Galactose and alpha-D-Fructose.
Explanation: Sucrose is a non-reducing disaccharide composed of alpha-D-glucose and beta-D-fructose linked by an alpha(1->2) glycosidic bond involving the anomeric carbon C1 of glucose and C2 of fructose.
10Why is cellulose insoluble in water and structural in function, whereas glycogen is easily mobilized for energy storage?
A.Cellulose contains alpha(1->4) linkages forming helical coils, while glycogen consists of unbranched beta chains.
B.Cellulose consists of linear beta(1->4) D-glucose chains stabilized by interchain hydrogen bonds; glycogen has branched alpha(1->4) and alpha(1->6) bonds.
C.Cellulose is composed of amino sugars with acetyl group modifications, while glycogen lacks hydroxyl groups.
D.Cellulose is synthesized in mitochondria, whereas glycogen is stored in plant cell walls.
Explanation: Cellulose consists of unbranched linear chains of D-glucose linked by beta(1->4) glycosidic bonds. These straight microfibrils pack densely with extensive inter-chain hydrogen bonding. Glycogen contains alpha(1->4) main chains with frequent alpha(1->6) branches, making it compact and readily accessible to glycogen phosphorylase.

About the Extremadura PAU Biology Exam

The Extremadura PAU Biology examination (Pruebas de Acceso a la Universidad 2026) is the official standardized assessment for 2º Bachillerato students seeking university entry in Extremadura (UEx). The exam evaluates student mastery across five key biological domains: Biomolecules & Chemical Basis of Life, Cellular Structure & Membrane Transport, Cell Metabolism, Molecular Genetics & Biotechnology, and Microbiology & Immunology. This practice bank provides 100 high-quality questions with comprehensive explanations for all options.

Exam sponsor: Comisión Organizadora de la PAU de Extremadura (Universidad de Extremadura - UEx / Consejería de Educación de la Junta de Extremadura). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

90-minute written examination (data interpretation, biochemical pathways, problem solving; local questions are an English-language MCQ study adaptation)

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 78.26 ordinary registration fee for PAU (50% discount EUR 39.13 for general large family; full exemption for special large family, disability, or terrorism victims).

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.

20%

Biomolecules & Chemical Basis of Life

Bioelementos, agua y sales minerales, estructura y función de glúcidos, lípidos, proteínas, enzimas y ácidos nucleicos.

20%

Cellular Structure, Organelles & Membrane Transport

Organización celular procariota y eucariota, membrana plasmática, transporte membranoso, sistema de endomembranas, orgánulos, ciclo celular, mitosis y meiosis.

20%

Cell Metabolism: Bioenergetics, Respiration & Photosynthesis

Anabolismo y catabolismo, cinética enzimática, glucólisis, fermentaciones, ciclo de Krebs, cadena de transporte electrónico, fosforilación oxidativa y fotosíntesis.

20%

Molecular Genetics, Gene Expression & Biotechnology

Replicación del ADN, transcripción, traducción, código genético, regulación de la expresión génica, mutaciones, ingeniería genética y biotecnología.

20%

Microbiology, Immunology & Infectious Diseases

Clasificación de microorganismos (virus, bacterias, hongos), microbiología aplicada, inmunidad innata y adaptativa, respuesta humoral y celular, antígenos, anticuerpos y vacunación.

Preparing for the Extremadura 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: 90-minute written examination (data interpretation, biochemical pathways, problem solving; local questions are an English-language MCQ study adaptation)
  • Time limit: 90 minutes (1.5 hours)
  • Exam / certification fees: EUR 78.26 ordinary registration fee for PAU (50% discount EUR 39.13 for general large family; full exemption for special large family, disability, or terrorism victims). Official sources

Using Our Practice Resources

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

Extremadura PAU Biology: Suggested Study Strategy

1Master biomolecule structures and bonds (glycosidic, ester, peptide, phosphodiester) and water's physicochemical properties.
2Review organelle functions, endomembrane trafficking, and passive vs active cell membrane transport mechanisms.
3Trace key metabolic pathways including intracellular locations, substrates, and ATP yields (glycolysis, Krebs cycle, oxidative phosphorylation, Calvin cycle).
4Practice molecular genetics problems (DNA replication, transcription, translation, genetic code) and Mendelian inheritance crosses.
5Differentiate innate vs adaptive immunity, humoral vs cellular responses, and primary vs secondary immunization.

Frequently Asked Questions

What is the format of the Extremadura PAU exam?

The exam is a 90-minute written examination testing Bachillerato subject content.

What score is required to pass?

A minimum score of 4.0 out of 10 in the Access Phase is required to calculate the university admission mark.