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100+ Free Castilla-La Mancha PAU Biology (Biología - UCLM 2026) Practice Questions
Castilla-La Mancha PAU Biology / Biología 2º Bachillerato UCLM 2026 (Pruebas de Acceso a la Universidad) practice questions are available now; exam metadata is being verified.
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2026 Statistics
Key Facts: Castilla-La Mancha PAU Biology (Biología - UCLM 2026) Exam
90 min
Exam duration (1.5 hours)
UCLM PAU Tribunal
0–10
Grading scale
PAU Castilla-La Mancha Regulations
4.0
Minimum mark in Access Phase to average with Bachillerato GPA
Spanish University Access Regulations
100
Practice questions in this OpenExamPrep question bank
OpenExamPrep
Castilla-La Mancha PAU Biology (UCLM 2026) is a 90-minute exam evaluating 2º Bachillerato biology mastery across 5 core topic areas. This English-language multiple-choice bank is a study adaptation of the official written PAU paper, not a replica of it.
Sample Castilla-La Mancha PAU Biology (Biología - UCLM 2026) Practice Questions
Try these sample questions to test your Castilla-La Mancha PAU Biology (Biología - UCLM 2026) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1Which property of water is primarily responsible for its capacity to act as a thermal buffer in living beings?
A.Its high specific heat, which allows it to absorb or release large amounts of heat with little change in its temperature
B.Its low heat of vaporization, which facilitates evaporation at low temperatures
C.Its lower density in the liquid state than in the solid state
D.Its high dielectric constant, which dissolves polar compounds
Explanation: The high specific heat of water is due to the large amount of energy needed to break the hydrogen bonds between its molecules before increasing their kinetic energy. This allows water to function as an excellent thermal buffer, protecting cells against abrupt temperature changes.
2What happens to a human red blood cell when it is placed in a hypotonic solution?
A.It undergoes crenation due to massive loss of water to the exterior
B.Water enters massively by osmosis, increasing its volume until causing its lysis or hemolysis
C.It remains unaltered because the cell membrane is totally impermeable to water
D.It loses mineral salts by active transport until balancing the osmotic pressure
Explanation: In a hypotonic medium (lower solute concentration than the cell interior), water enters the red blood cell along the osmotic gradient. Lacking a rigid cell wall, the animal cell swells and eventually bursts, a process called hemolysis.
3By what type of bond do two monosaccharides join to form a disaccharide with the release of a water molecule?
A.Peptide bond
B.Phosphodiester bond
C.O-glycosidic bond
D.Ester bond
Explanation: The O-glycosidic bond is established between the hydroxyl group (-OH) of the anomeric carbon of one monosaccharide and a hydroxyl group of another monosaccharide, undergoing condensation and releasing a water molecule.
4What is the main energy-reserve polysaccharide in animals?
A.Starch
B.Cellulose
C.Chitin
D.Glycogen
Explanation: Glycogen is a branched polymer of alpha-D-glucose stored in the liver and skeletal muscles of humans and other animals as a fast glucose reserve.
5What chemical components make up a triacylglycerol (triglyceride) molecule?
A.A glycerol molecule joined by ester bonds to three fatty acid molecules
B.Three sphingosine molecules joined to a phosphate group
C.A cholesterol molecule esterified with two isoprene chains
D.Two glucose molecules joined to a saturated hydrocarbon chain
Explanation: Triacylglycerols are neutral saponifiable lipids formed by esterification of the three hydroxyl groups of glycerol (propanetriol) with three fatty acid molecules (same or different).
6What structural property of phospholipids explains the spontaneous formation of the lipid bilayer in aqueous medium?
A.Their capacity to form hydrophobic peptide bonds
B.Their amphipathic character, with a polar hydrophilic head and apolar hydrophobic tails
C.Their high rigidity conferred by the aromatic rings of their fatty acid chains
D.Their total insolubility and absence of electrically charged groups
Explanation: Phospholipids are amphipathic molecules: the head (phosphate and alcohol) is polar and interacts with water, while the tails (hydrocarbon chains of fatty acids) are apolar and hydrophobic. This causes them to self-assemble in water forming lipid bilayers.
7How is the primary structure of a protein defined?
A.The global three-dimensional folding of the polypeptide chain
B.The association of several independent polypeptide subunits
C.The linear sequence of amino acids joined by peptide bonds
D.The local spatial arrangement in alpha helix or beta sheet
Explanation: The primary structure is the most elementary level of protein organization and corresponds to the specific linear order in which amino acids are chained from the amino-terminal end to the carboxyl-terminal end.
8What happens during the denaturation of a protein due to heat or a drastic pH change?
A.Covalent peptide bonds are broken, fragmenting the protein into free amino acids
B.The nucleotide sequence of the gene encoding it is altered
C.The disulfide bridges of the primary structure are hydrolyzed
D.Weak bonds (H bridges, ionic and hydrophobic interactions) break, losing the functional three-dimensional conformation
Explanation: Denaturation involves the loss of secondary, tertiary, and quaternary structures through the rupture of non-covalent bonds and weak interactions. The peptide bonds of the primary structure remain intact.
9How does a competitive inhibitor act on enzyme activity?
A.It binds to the active site of the enzyme preventing substrate binding; its effect is reversed by increasing the substrate concentration
B.It binds to an allosteric site, irreversibly altering the shape of the active site regardless of substrate concentration
C.It binds exclusively to the enzyme-substrate complex, destroying the substrate molecule by oxidation
D.It increases the activation energy of the reaction without altering the affinity for the substrate
Explanation: The competitive inhibitor has a chemical structure similar to that of the substrate and competes for the active site of the enzyme. By increasing the substrate concentration ([S]), the probability that the substrate binds increases and the same Vmax is reached.
10What biological function do the organic cofactors known as coenzymes (e.g. NAD+, FAD) perform?
A.They act as structural components of the plant cell wall
B.They temporarily transport chemical groups, electrons, or protons during oxidation-reduction enzymatic reactions
C.They permanently bind to the substrate to increase the Gibbs free energy
D.They form the transfer RNA mold during gene transcription
Explanation: Coenzymes such as NAD+ (nicotinamide adenine dinucleotide) and FAD are non-protein organic molecules that act as acceptors and donors of electrons and protons in redox metabolic reactions, being reversibly oxidized and reduced.
About the Castilla-La Mancha PAU Biology (Biología - UCLM 2026) Practice Questions
Verified exam format metadata for Castilla-La Mancha PAU Biology / Biología 2º Bachillerato UCLM 2026 (Pruebas de Acceso a la Universidad) is pending. The practice questions above remain available while official exam length, timing, passing score, fee, and administrator details are reviewed.