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Exam Review

Key Facts: Cantabria PAU Biology Exam

90 Minutes

Official examination duration

UNICAN PAU Regulations

Min 4.0

Minimum Access Phase score required

UNICAN PAU Guidelines

6 Blocks

Official saberes: biomolecules, molecular genetics, cell biology, metabolism, biotechnology, immunology

UNICAN Criterios de Corrección PAU Biología 2026

EUR 71.09

Base registration fee for PAU Access Phase

UNICAN Fees

100

Practice questions available in this question bank

OpenExamPrep

Cantabria PAU Biology (UNICAN 2026) is a 90-minute Spanish written exam across six official blocks (biomolecules, molecular genetics, cell biology, metabolism, biotechnology, immunology). This English-language MCQ bank is a study adaptation, not a format simulation.

Sample Cantabria PAU Biology Practice Questions

Try these sample questions to review concepts for the Cantabria 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 allows homeothermic organisms to keep a stable body temperature through evaporation of sweat?
A.High heat of vaporization due to intermolecular hydrogen bonds.
B.Low boiling point caused by nonpolar covalent bonds.
C.Higher density in the solid state than in the liquid state.
D.Low surface tension that favors hydrophobic cohesion.
Explanation: Water has a high heat of vaporization (about 540 cal/g at 100 °C) because a large amount of thermal energy is needed to break its dense network of intermolecular hydrogen bonds before molecules enter the gas phase. That energy absorption cools the body efficiently when sweat evaporates from the skin.
2What happens to a human erythrocyte placed in a saline solution that is hypertonic relative to its cytoplasm?
A.It takes up water by osmosis until it undergoes lysis or hemolysis.
B.It loses water by osmosis to the external medium and undergoes crenation (shriveling).
C.It takes up Na+ ions by simple diffusion, increasing cell volume.
D.It remains unchanged because the membrane is completely impermeable to water.
Explanation: In a hypertonic medium, solute concentration is higher outside than inside the erythrocyte. Water therefore leaves the cell by osmosis down the water-potential gradient, shrinking cytoplasmic volume and producing the wrinkled appearance called crenation.
3What is the main function of the bicarbonate buffer system (HCO3− / H2CO3) in human blood plasma?
A.To catalyze hydrolysis of plasma proteins during physiological exercise.
B.To raise osmotic pressure by irreversibly precipitating calcium phosphate salts.
C.To keep plasma pH within physiological limits (about 7.35–7.45).
D.To transport dietary triglycerides directly to adipose tissue.
Explanation: The bicarbonate buffer dampens pH swings in blood plasma. When proton concentration rises, HCO3− binds H+ to form H2CO3, which dissociates into CO2 and H2O, helping keep physiological pH stable.
4How do the α and β anomers of D-glucopyranose differ structurally in aqueous solution?
A.In the total number of carbon atoms in the hydrocarbon chain.
B.In having a ketone group instead of an aldehyde group in the open-chain form.
C.In the ability to form peptide bonds with aromatic amino acids.
D.In the spatial orientation of the hydroxyl (–OH) attached to the anomeric carbon (C1).
Explanation: When D-glucose cyclizes to glucopyranose, carbonyl carbon C1 becomes a new asymmetric anomeric carbon. If the C1 –OH points down in the Haworth projection (trans to C6), the sugar is the α anomer; if it points up (cis to C6), it is the β anomer.
5Why does sucrose (α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside) lack reducing power toward Fehling’s reagent?
A.Because both anomeric carbons (C1 of glucose and C2 of fructose) are involved in the glycosidic bond.
B.Because it contains only galactose units linked by β(1→4) bonds.
C.Because its structure completely lacks hydroxyl groups on the furanose rings.
D.Because it denatures rapidly at room temperature, releasing carbon monoxide.
Explanation: Reducing power depends on a free carbonyl (aldehyde or ketone) at an anomeric carbon. In sucrose, the dicarbonyl glycosidic link joins the anomeric C1 of α-D-glucose to the anomeric C2 of β-D-fructose, so both anomeric carbons are locked and no free reducing group remains.
6Which structural feature explains cellulose’s high mechanical strength and insolubility compared with starch?
A.Starch has β(1→4) linkages that form very compact branched helices.
B.Cellulose consists of linear β-D-glucose polymers joined by β(1→4) bonds that form interchain hydrogen bonds.
C.Cellulose contains N-acetylglucosamine monomers covalently joined by amide bonds.
D.Starch is a heteropolysaccharide with a strict alternating glucose–ribose pattern.
Explanation: Cellulose is a structural homopolysaccharide of β-D-glucose linked by β(1→4) bonds. That geometry yields straight parallel chains that pack tightly through interchain hydrogen bonds into strong, insoluble microfibrils.
7Why do unsaturated fatty acids with cis double bonds have lower melting points than saturated fatty acids of the same chain length?
A.Because saturated chains form additional hydrogen bonds with surrounding water molecules.
B.Because cis unsaturations completely remove the electrical charge of the terminal carboxyl group.
C.Because cis double bonds kink the hydrocarbon chain and hinder lipid packing.
D.Because unsaturated fatty acids spontaneously polymerize into high-density crystalline networks.
Explanation: Cis double bonds introduce a fixed bend in the hydrocarbon chain. That angular geometry prevents tight linear packing through van der Waals contacts, so less thermal energy is needed to melt them.
8What does saponification of a triacylglycerol (triglyceride) consist of?
A.Dehydrating condensation of three glycerol molecules with one long-chain fatty acid.
B.Catalytic oxidation of double bonds to produce volatile aldehydes and ketones.
C.Enzymatic addition of phosphate groups to glycerol hydroxyls to synthesize nucleotides.
D.Alkaline hydrolysis of the ester bonds between glycerol and fatty acids, releasing glycerol and sodium/potassium fatty-acid salts (soaps).
Explanation: Saponification is hydrolysis of triacylglycerol ester bonds by a strong base (NaOH or KOH). The esters break, releasing one glycerol (propanetriol) and three alkali fatty-acid salts commonly called soaps.
9Which structural property lets glycerophospholipids spontaneously organize into bilayers in water?
A.Their amphipathic nature: a hydrophilic polar head (phosphate and alcohol) and two hydrophobic nonpolar fatty-acid tails.
B.Peptide bonds covalently joining the fatty acids to the polar head.
C.Complete water solubility because they lack hydrocarbon chains longer than three carbons.
D.An exclusive ability to act as photosynthetic pigments that capture infrared light.
Explanation: Phospholipids are amphipathic: a hydrophilic head (glycerol, phosphate, and an amino alcohol) and a hydrophobic region (two fatty-acid tails). In water, tails face inward and polar heads face the aqueous phases, forming the lipid bilayer.
10What is cholesterol’s role in regulating plasma-membrane fluidity in animal cells?
A.It indefinitely increases permeability so large hydrophilic proteins pass freely.
B.It buffers fluidity: at high temperature it reduces lipid mobility, and at low temperature it hinders packing and freezing.
C.It blocks mitochondrial ATP synthesis by inhibiting active proton transport.
D.It completely replaces phospholipids in the outer leaflet of a cellulosic bilayer.
Explanation: Cholesterol acts as a dual fluidity buffer in animal plasma membranes. At higher physiological temperatures its rigid sterol ring restrains excessive fatty-acid motion; at lower temperatures it intercalates between chains and prevents tight packing and crystallization.

About the Cantabria PAU Biology Exam

The Cantabria PAU Biology examination (Pruebas de Acceso a la Universidad 2026) is the official standardized assessment for 2º Bachillerato students seeking university entry in Cantabria (UNICAN). 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: University of Cantabria (UNICAN) PAU Organising Commission. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Official UNICAN PAU Biología 2026 paper: 90 minutes; 13 open/semi-constructed tasks in 6 saberes blocks (A biomolecules, B molecular genetics, C cell biology, D metabolism, E biotechnology, F immunology); candidates answer 8 tasks (1+1+2+2+1+1) worth 1.25 points each. This practice bank is an English-language MCQ study adaptation, not a format simulation.

Time Limit

90 minutes

Passing Score

Marked on a 0–10 scale. Minimum 4.0 required in Access Phase.

Exam / Certification Fees

EUR 71.09 base registration fee for PAU Access Phase.

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.

12.5%

A. Biomolecules

Las biomoléculas — structure/function of water, salts, carbohydrates, lipids, proteins/enzymes, and nucleic acids (official Apartado 1; 1 obligatory task).

12.5%

B. Molecular genetics

Genética molecular — replication, transcription, translation, genetic code, mutation, and gene expression (official Apartado 2; 1 obligatory task).

25%

C. Cell biology

Biología celular — prokaryote/eukaryote organization, membranes, organelles, cytoskeleton, cycle/mitosis/meiosis (official Apartado 3; 2 obligatory tasks).

25%

D. Metabolism

Metabolismo — bioenergetics, glycolysis/fermentations, respiration, photosynthesis, and pathway integration (official Apartado 4; 2 obligatory tasks).

12.5%

E. Biotechnology

Biotecnología — recombinant DNA, restriction enzymes, PCR, and industrial/medical applications (official Apartado 5; 1 obligatory task).

12.5%

F. Immunology

Inmunología — innate/adaptive immunity, antibodies, MHC, complement, vaccines, and immune disorders (official Apartado 6; 1 obligatory task).

Preparing for the Cantabria PAU Biology Exam

What You Need to Know

  • Passing score: Marked on a 0–10 scale. Minimum 4.0 required in Access Phase.
  • Assessment: Official UNICAN PAU Biología 2026 paper: 90 minutes; 13 open/semi-constructed tasks in 6 saberes blocks (A biomolecules, B molecular genetics, C cell biology, D metabolism, E biotechnology, F immunology); candidates answer 8 tasks (1+1+2+2+1+1) worth 1.25 points each. This practice bank is an English-language MCQ study adaptation, not a format simulation.
  • Time limit: 90 minutes
  • Exam / certification fees: EUR 71.09 base registration fee for PAU Access Phase. 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

Cantabria 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

Is this practice bank in the same format as the real exam?

No. The official exam is a 90-minute written examination in Spanish with open-ended and constructed-response tasks. This bank is an English-language multiple-choice study adaptation.