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Free Practice Questions for Castilla y León PAU Biology

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Exam Review

Key Facts: Castilla y León PAU Biology Exam

90 min

Exam Time Limit

Comisión Organizadora PAU Castilla y León

0–10

Grading Scale

Junta de Castilla y León

4.0

Min. Access Phase Score

USAL / UVA / UBU / ULE

EUR 76-90

Base Registration Fee

Junta de Castilla y León

5 Blocks

Curriculum Content Areas

2º Bachillerato Biology Syllabus

The Castilla y León PAU Biology exam (Biología) is administered by the public universities of Castilla y León (USAL, UVA, UBU, ULE) and the Junta de Castilla y León for students completing 2nd Bachillerato. The exam lasts 90 minutes and is graded on a 0–10 scale (minimum 4.0 required in the Access Phase). Note that local questions on this platform are an English-language MCQ study adaptation created to help students master the underlying 2nd Bachillerato curriculum.

Sample Castilla y León PAU Biology Practice Questions

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

1Which physical property of water allows it to absorb or release large quantities of thermal energy with minimal change in its own temperature, buffering biological organisms against environmental thermal fluctuations?
A.High specific heat capacity
B.High surface tension
C.Low latent heat of vaporization
D.Maximum density at 0 °C
Explanation: Water possesses a high specific heat capacity (4.184 J/g·°C) due to its extensive intermolecular hydrogen-bonding network. Heat energy supplied to water is predominantly consumed in breaking hydrogen bonds before increasing the kinetic energy of individual water molecules, thus moderating internal body temperatures and aquatic habitats.
2When a red blood cell (erythrocyte) is placed in a hypertonic NaCl solution, water rapidly flows out of the cell across the plasma membrane. What is this cellular response termed in animal cell physiology?
A.Crenation
B.Plasmolysis
C.Hemolysis
D.Turgor
Explanation: In animal cells lacking a cell wall, placement in a hypertonic environment causes osmotic loss of intracellular water, leading to cell shrinkage and a spiky surface appearance known as crenation. In plant cells with rigid cell walls, the equivalent protoplast detachment is termed plasmolysis.
3Which of the following monosaccharides is classified structural-chemically as a ketohexose?
A.D-Fructose
B.D-Glucose
C.D-Galactose
D.D-Ribose
Explanation: D-Fructose is a 6-carbon monosaccharide (hexose) containing a ketone functional group at carbon 2, classifying it as a ketohexose. D-Glucose and D-Galactose are aldohexoses, whereas D-Ribose is an aldopentose.
4Maltose is a disaccharide produced by starch hydrolysis. Which glycosidic linkage connects the two glucose units in maltose?
A.alpha(1 -> 4) glycosidic bond
B.beta(1 -> 4) glycosidic bond
C.alpha(1 -> 2) glycosidic bond
D.alpha(1 -> 6) glycosidic bond
Explanation: Maltose consists of two D-glucopyranose units linked by an alpha(1 -> 4) glycosidic bond formed via a condensation reaction between the anomeric hydroxyl of alpha-D-glucose (C1) and the C4 hydroxyl of another glucose molecule.
5Cellulose serves as a structural component in plant cell walls, whereas starch serves as energy storage. What structural feature accounts for the mechanical rigidity and resistance of cellulose to human digestive enzymes?
A.Linear unbranched chains of D-glucose linked by beta(1 -> 4) glycosidic bonds forming microfibrils
B.Branched polymer chains of D-glucose linked by alpha(1 -> 4) and alpha(1 -> 6) bonds
C.Coiled helical chains of D-glucose linked exclusively by alpha(1 -> 4) bonds
D.Heteropolysaccharide composition containing alternating units of N-acetylglucosamine
Explanation: Cellulose is composed of unbranched linear chains of D-glucose connected by beta(1 -> 4) glycosidic linkages. This geometry allows parallel glucose chains to form extensive interchain hydrogen bonds, creating insoluble microfibrils with high tensile strength that human alpha-amylases cannot hydrolyze.
6Which of the following lipid classes is non-saponifiable because it lacks fatty acid components connected by ester linkages?
A.Steroids (e.g., cholesterol)
B.Triacylglycerols (triglycerides)
C.Glycerophospholipids (phosphatidylcholine)
D.Sphingolipids (sphingomyelin)
Explanation: Steroids are non-saponifiable lipids derived from a tetracyclic cyclopentanoperhydrophenanthrene ring structure. Because they contain no esterified fatty acids, they do not undergo alkaline hydrolysis (saponification) to yield soap (fatty acid salts).
7Phospholipids self-assemble into lipid bilayers when introduced into an aqueous environment. What molecular property drives this spontaneous formation?
A.Amphipathic structure with hydrophilic polar heads and hydrophobic non-polar fatty acid tails
B.Complete hydrophobicity across all regions of the hydrocarbon skeleton
C.High solubility in polar solvents mediated by ionic carboxylate groups
D.Covalent cross-linking between adjacent fatty acid tails
Explanation: Phospholipids are amphipathic molecules containing a polar hydrophilic head (phosphate and attached group) and two non-polar hydrophobic tail regions (fatty acid chains). In water, hydrophobic interactions drive the non-polar tails inward away from water while hydrophilic heads face the aqueous environment, yielding a stable bilayer.
8Oleic acid is a monounsaturated 18-carbon fatty acid with a cis double bond at carbon 9. How does the presence of this cis double bond affect its physical melting point compared to stearic acid (saturated 18C)?
A.It lowers the melting point by creating a kink in the hydrocarbon chain that disrupts intermolecular packing
B.It increases the melting point by enhancing van der Waals packing density
C.It elevates the melting point due to increased molecular weight
D.It has no effect on physical melting temperature
Explanation: A cis double bond introduces a rigid bend (kink) in the fatty acid hydrocarbon chain. This prevents tight, parallel van der Waals packing among acyl chains, lowering the thermal energy required to disrupt the lattice and resulting in a lower melting point (liquid at room temperature).
9At physiological pH (~7.4), a standard amino acid lacking an ionizable side chain exists predominantly in which ionic state?
A.Zwitterion (dipolar ion with protonated -NH3+ and deprotonated -COO-)
B.Fully protonated cation (+1 charge)
C.Fully deprotonated anion (-1 charge)
D.Uncharged neutral non-polar molecule
Explanation: At physiological pH (~7.4), which is between the carboxyl pKa (~2.0) and amino pKa (~9.5), the alpha-carboxyl group loses a proton (-COO-) while the alpha-amino group retains a proton (-NH3+). The amino acid exists as a zwitterion with a net electrical charge of zero.
10Which of the following characteristics accurately describes the chemical nature of the peptide bond joining adjacent amino acid residues in proteins?
A.Planar amide linkage with partial double-bond character that restricts free rotation around the C-N bond
B.Flexible single covalent bond allowing unrestricted 360-degree rotation
C.Weak non-covalent hydrogen bond easily broken by mild temperature increases
D.Ionic interaction formed between positively and negatively charged side chains
Explanation: The peptide bond (-CO-NH-) is a covalent amide linkage formed by condensation. Resonance delocalization of electron pairs between the carbonyl oxygen and amide nitrogen imparts a ~40% double-bond character to the C-N bond, freezing the six backbone atoms in a rigid planar trans conformation.

About the Castilla y León PAU Biology Exam

The Castilla y León PAU Biology exam (Biología 2º Bachillerato) evaluates secondary school graduates across Castilla y León on core life science disciplines including biochemistry, cellular biology, energetics, molecular genetics, microbiology, and immunology. Please note: The official PAU exam features written structured/essay questions in Spanish; the 100 questions provided here are an English-language multiple-choice study adaptation designed for self-assessment and core concept mastery.

Exam sponsor: Comisión Organizadora de las Pruebas de Acceso a la Universidad de Castilla y León (USAL, UVA, UBU, ULE). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

90-minute written examination (traditionally open-ended/structured questions; 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 76.82 base registration fee for PAU Access Phase (plus EUR 10.33 per voluntary subject) set by Junta de Castilla y León.

Exam sponsor website

Reported exam pass rate: High (~85-95% PAU overall pass rate in Castilla y León). This describes exam candidates, not OpenExamPrep users or results from using our resources. 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.

25%

Biomolecules and Chemical Basis of Life

Chemical composition of living matter, water properties, mineral salts, osmotic phenomena, pH buffers, monosaccharides, oligosaccharides, polysaccharides, lipids (saponifiable and non-saponifiable), proteins, amino acid structure, peptide bonds, levels of protein conformation, enzyme catalysts, and nucleic acid structure (DNA double helix and RNA types).

25%

Cell Biology and Cellular Organization

Cell theory, prokaryotic versus eukaryotic structural organization, plasma membrane fluid mosaic model, active and passive transport mechanisms, endomembrane system (ER, Golgi, lysosomes, peroxisomes), mitochondria, chloroplasts, cytoskeleton, nucleus, chromatin, mitosis phases, cytokinesis, and meiosis (crossing over and reductional division).

20%

Metabolism and Cellular Energetics

Anabolism and catabolism concepts, ATP and electron carriers, enzyme kinetics and inhibition, glycolysis, pyruvate oxidation, Krebs cycle, mitochondrial electron transport and oxidative phosphorylation, lactic and alcoholic fermentations, chloroplast light reactions (photolysis, photophosphorylation), and Calvin cycle carbon fixation.

15%

Genetics and Molecular Biology

Semi-conservative DNA replication mechanism and enzymes, transcription in prokaryotes and eukaryotes, RNA splicing, genetic code characteristics, translation initiation, elongation and termination, gene/chromosomal/genomic mutations, and Mendelian inheritance principles.

15%

Microbiology and Immunology

Structure of bacteria, archaea, viruses (lytic vs lysogenic cycles), viroids, and prions; innate barriers and phagocytosis; adaptive cellular and humoral responses; antibody structure and classes (IgG, IgM, IgA, IgE, IgD); MHC complexes; active vs passive immunity; vaccines; hypersensitivity; autoimmunity; and immunodeficiencies.

Preparing for the Castilla y León 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 (traditionally open-ended/structured questions; local questions are an English-language MCQ study adaptation)
  • Time limit: 90 minutes (1.5 hours)
  • Exam / certification fees: EUR 76.82 base registration fee for PAU Access Phase (plus EUR 10.33 per voluntary subject) set by Junta de Castilla y León. 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

Castilla y León PAU Biology: Suggested Study Strategy

1Master biomolecule structures, chemical linkages (glycosidic, ester, peptide, phosphodiester), and physical properties.
2Trace energy and carbon flow step-by-step through glycolysis, Krebs cycle, oxidative phosphorylation, and the Calvin cycle.
3Understand the mechanics of DNA replication, transcription, and translation, including enzyme roles and 5' to 3' polarity.
4Distinguish clearly between innate and adaptive immunity, humoral vs cellular responses, and primary vs secondary immune responses.
5Use diagrams and active recall to practice organelle functions, membrane transport, and stages of cell division.

Frequently Asked Questions

What is the format of the official Castilla y León PAU Biology exam?

The official Castilla y León PAU Biology exam is a 90-minute written examination administered in Spanish across public university centers (USAL, UVA, UBU, ULE), consisting of structured and short-answer questions. Note that the 100 questions available on this site are an English-language multiple-choice practice adaptation developed to help students test their knowledge of the official curriculum.

What is the passing score for Castilla y León PAU Biology?

The exam is graded on a 0–10 scale. In the Access Phase (Fase de Acceso), a minimum score of 4.0 is required to average with the Bachillerato GPA (which counts for 60% of the final university access score, while PAU counts for 40%, requiring a total average of >= 5.0).

What is the registration fee for the PAU exam in Castilla y León?

The registration fee in Castilla y León is set annually by the Junta de Castilla y León, typically ranging between EUR 76.00 and 90.00 for the Access Phase, with exemptions or discounts for large families (familia numerosa), disabled students, or victims of terrorism.

Which universities manage the PAU exam in Castilla y León?

The examination is coordinated by the Commission of Universities of Castilla y León comprising Universidad de Salamanca (USAL), Universidad de Valladolid (UVA), Universidad de Burgos (UBU), and Universidad de León (ULE), under the authority of the Junta de Castilla y León.

Why are the practice questions here in English and in multiple-choice format?

These questions serve as an English-language MCQ study adaptation designed for international students, bilingual program candidates, and revision learners seeking to test core biology concepts tested on the Castilla y León 2nd Bachillerato curriculum.