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100+ Free Aragón PAU Biology Practice Questions
Aragón PAU Biology (Biología 2º Bachillerato) practice questions are available now; exam metadata is being verified.
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About 95% of Bachillerato candidates passed the Aragón PAU Access Phase in the June 2025 ordinary sitting (regional reported results). Pass Rate
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2026 Statistics
Key Facts: Aragón PAU Biology Exam
90 min
Exam Time Limit
UNIZAR PAU Commission
0–10
Grading Scale
Gobierno de Aragón / UNIZAR
4.0
Min. Access Phase Score
PAU Access Rules
EUR 75.00
Ordinary Registration Fee
UNIZAR PAU inscription page 2026
6 Blocks
Basic Knowledge Syllabus Areas
2º Bachillerato Biology Curriculum
The Aragón PAU Biology exam (Biología) is organized by the PAU Organising Commission of Aragón and Universidad de Zaragoza (UNIZAR) for 2nd Bachillerato students. The 90-minute exam is scored on a 0–10 scale (minimum 4.0 required in Access Phase). Our 100-question practice set provides an English-language MCQ study tool covering the complete 2nd Bachillerato biology curriculum.
Sample Aragón PAU Biology Practice Questions
Try these sample questions to test your Aragón PAU Biology exam readiness. 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 is primarily responsible for its ability to absorb large amounts of heat energy without experiencing a drastic change in temperature?
A.High specific heat capacity
B.High surface tension
C.Low latent heat of vaporization
D.Maximum density at 0 °C
Explanation: Water has a high specific heat capacity (4.184 J/g·°C) due to its extensive intermolecular hydrogen bonding network. Absorbed thermal energy is initially consumed in breaking these hydrogen bonds rather than immediately increasing molecular kinetic energy, stabilizing intracellular temperatures and aquatic environments.
2The upward movement of water through xylem vessels in tall plants relies on the force of attraction between water molecules and the hydrophilic cell walls of vessel elements. What is this phenomenon called?
A.Adhesion
B.Cohesion
C.Viscosity
D.Plasmolysis
Explanation: Adhesion refers to the attractive forces between water molecules and different polar or charged surfaces, such as the cellulose and lignin in xylem walls. Cohesion is the attraction between water molecules themselves. Together, cohesion and adhesion support transpirational pull under tension.
3What primary buffer system maintains human blood plasma pH within the narrow physiological range of 7.35 to 7.45?
A.Ammonium buffer system
B.Phosphate buffer system
C.Bicarbonate / carbonic acid buffer system
D.Acetate buffer system
Explanation: The carbonic acid-bicarbonate buffer system (H2CO3 / HCO3-) is the primary extracellular buffer in human blood. Excess hydrogen ions are neutralized by bicarbonate to form carbonic acid, which dissociates into water and carbon dioxide exhaled by the lungs.
4When human red blood cells are placed in a concentrated (hypertonic) sodium chloride solution, water leaves the cells by osmosis. What happens to the erythrocytes?
A.Turgor
B.Plasmolysis
C.Hemolysis
D.Crenation
Explanation: In a hypertonic extracellular environment, water exits animal cells down its water potential gradient, causing red blood cells to shrink and form notched, spiny surfaces—a process termed crenation. Hemolysis occurs in hypotonic media.
5Which inorganic bioelement functions as an essential cofactor for chlorophyll and is required for muscle contraction and enzymatic ATP cleavage?
A.Potassium (K+)
B.Calcium (Ca2+)
C.Iron (Fe2+/Fe3+)
D.Magnesium (Mg2+)
Explanation: Magnesium (Mg2+) is the central metal ion in the porphyrin ring of chlorophyll molecules. It also acts as an essential cofactor for kinases and ATPases, stabilizing ATP complexes during enzymatic reactions.
6Which of the following monosaccharides is structurally classified as a ketohexose?
A.D-Galactose
B.D-Fructose
C.D-Ribose
D.D-Glucose
Explanation: D-Fructose contains six carbon atoms (hexose) and a ketone functional group at C2 (ketohexose). In aqueous solution, it predominantly forms a five-membered furanose ring. D-Glucose and D-Galactose are aldohexoses.
7Which disaccharide is non-reducing because its glycosidic bond involves the anomeric carbon atoms of both constituent monosaccharides (alpha-D-glucopyranosyl-(1->2)-beta-D-fructofuranoside)?
A.Lactose
B.Sucrose
C.Cellobiose
D.Maltose
Explanation: Sucrose is formed by an alpha(1->2) glycosidic linkage between C1 of alpha-D-glucose and C2 of beta-D-fructose. Because both anomeric carbons are engaged in the bond, no free hemiacetal or hemiketal group remains to reduce Benedict's or Fehling's reagents.
8Which structural polysaccharide consists of unbranched chains of D-glucose molecules joined by beta-1,4-glycosidic bonds, forming rigid microfibrils in plant cell walls?
A.Cellulose
B.Amylose
C.Glycogen
D.Chitin
Explanation: Cellulose is an unbranched polymer of glucose connected by beta-1,4-glycosidic bonds. Hydrogen bonding between adjacent parallel linear chains forms rigid microfibrils that provide tensile strength to plant cell walls.
9Triacylglycerols (triglycerides) are classified as saponifiable lipids because they contain which chemical linkage between glycerol and three fatty acid chains?
A.Ester linkage
B.Ether linkage
C.Peptide bond
D.Phosphodiester bond
Explanation: Triacylglycerols are formed by condensation reactions establishing three ester linkages between the three hydroxyl groups of glycerol and the carboxyl groups of three fatty acids. Alkaline hydrolysis (saponification) cleaves ester bonds to release glycerol and fatty acid salts (soaps).
10Glycerophospholipids spontaneously assemble into lipid bilayers in aqueous environments due to their amphipathic nature. Which component forms the hydrophilic polar head group?
A.Hydrocarbon tail of a saturated fatty acid
B.Hydrocarbon tail of an unsaturated fatty acid
C.Phosphate group bonded to an alcohol (e.g., choline, ethanolamine, or serine)
D.Glycerol backbone esterified to three fatty acids
Explanation: Glycerophospholipids possess a hydrophilic head consisting of a negatively charged phosphate group linked to a polar head group alcohol (such as choline, ethanolamine, or serine) attached to C3 of glycerol. The two fatty acid chains attached to C1 and C2 constitute the hydrophobic tails.
About the Aragón PAU Biology Practice Questions
Verified exam format metadata for Aragón PAU Biology (Biología 2º Bachillerato) is pending. The practice questions above remain available while official exam length, timing, passing score, fee, and administrator details are reviewed.