Basque PAU Biology cheat sheet
Basque PAU Biology · Keep the key ideas within reach.
Biomolecules: water, carbohydrates, lipids, proteins, enzymes, nucleic acids
Water: polar molecule; cohesion and high specific heat (≈4.18 J/g·°C) buffer temperature; high latent heat of vaporisation (≈2260 J/g) aids cooling; solvent for ions and polar molecules; density maximum at 4 °C lets ice float and insulate water bodies.
Carbohydrates: monosaccharides (glucose C6H12O6, ribose C5H10O5) joined by glycosidic bonds (condensation, water released). Disaccharides: maltose = glucose+glucose, sucrose = glucose+fructose, lactose = glucose+galactose. Storage: starch (amylose α-1,4; amylopectin α-1,4 + α-1,6), glycogen; structural: cellulose (β-1,4) and chitin.
Lipids: triglycerides = glycerol + 3 fatty acids via ester bonds; saturated fatty acids have no C=C (solid, animal), unsaturated have C=C (liquid, plant). Phospholipids are amphipathic (hydrophilic head, hydrophobic tails) and form bilayers. Steroids (cholesterol) have four fused rings.
Proteins: amino acids joined by peptide bonds between –COOH and –NH2; primary (sequence), secondary (α-helix, β-sheet via H-bonds), tertiary (3D folding, disulfide bridges, hydrophobic interactions), quaternary (multiple polypeptides, e.g. haemoglobin).
Enzymes: globular protein catalysts lowering activation energy; active site is specific (lock-and-key / induced fit). Factors: temperature (denaturation above optimum, human ≈37 °C), pH (pepsin ≈2, amylase ≈7), substrate concentration, competitive (binds active site) vs non-competitive (binds allosteric site) inhibition.
Nucleic acids: nucleotides = pentose + phosphate + nitrogenous base. DNA: deoxyribose, bases A-T, G-C, double helix, antiparallel, H-bonds (2 A-T, 3 G-C). RNA: ribose, uracil replaces thymine, usually single-stranded.
ATP: adenosine triphosphate; hydrolysis ATP + H2O → ADP + Pi + energy (~30.5 kJ/mol) powers endergonic reactions; regenerated by respiration and photophosphorylation.
Test rules: Benedict's (reducing sugars → brick-red on heating), Fehling's, Lugol/Biuret (proteins → violet), Sudan III (lipids → red), Biuret for peptide bonds.
Cell biology: cell structure, organelles, membranes, transport, cell cycle and division
Prokaryote vs eukaryote: prokaryotes lack membrane-bound nucleus and organelles, have 70S ribosomes, circular DNA, peptidoglycan wall (bacteria); eukaryotes have nucleus, 80S ribosomes, membrane-bound organelles.
Organelles: nucleus (DNA, nucleolus makes rRNA), mitochondria (respiration, own DNA, cristae), chloroplasts (photosynthesis, thylakoids, stroma), rough ER (protein synthesis/transport), smooth ER (lipid synthesis), Golgi (modification/packaging), lysosomes (hydrolytic enzymes), ribosomes (protein synthesis), vacuole (turgor, storage), peroxisomes (catalase, H2O2).
Membrane: fluid mosaic model - phospholipid bilayer + integral/peripheral proteins, cholesterol (fluidity), glycoproteins (recognition). Selective permeability; small nonpolar molecules diffuse freely, ions and polar molecules need channels/carriers.
Transport: passive (diffusion, facilitated diffusion, osmosis - water high to low potential, aquaporins); active transport against gradient using ATP (Na+/K+ pump, 3 Na+ out/2 K+ in); endocytosis/exocytosis for bulk transport.
Osmosis in cells: animal cells lyse in hypotonic, crenate in hypertonic; plant cells become turgid in hypotonic (cell wall) and plasmolyse in hypertonic.
Cell cycle: interphase (G1 growth, S DNA replication, G2 preparation) + M phase (mitosis + cytokinesis). Mitosis: prophase (chromosomes condense), metaphase (align at equator), anaphase (chromatids separate), telophase (nuclear envelope reforms).
Meiosis: two divisions, crossing over in prophase I, independent assortment in metaphase I → four haploid cells; sources of genetic variation.
Checkpoints: G1/S and G2/M regulate cycle; loss of control → uncontrolled division (tumours). Apoptosis is programmed cell death.
Metabolism: catabolism and anabolism, respiration, photosynthesis, enzyme kinetics
Metabolism = catabolism (breakdown, releases energy, e.g. respiration) + anabolism (synthesis, consumes energy, e.g. photosynthesis, protein synthesis). ATP links the two.
Glycolysis: in cytoplasm, glucose → 2 pyruvate, net 2 ATP, 2 NADH.
Aerobic respiration: pyruvate → acetyl-CoA → Krebs cycle (mitochondrial matrix) yields NADH, FADH2, CO2, 2 ATP. Electron transport chain on inner membrane: NADH/FADH2 → ATP via oxidative phosphorylation (chemiosmosis), final electron acceptor O2, total ≈30–32 ATP per glucose.
Anaerobic respiration: in cytoplasm; in muscle pyruvate → lactate (2 ATP, NADH reoxidised); in yeast pyruvate → ethanol + CO2 (fermentation).
Photosynthesis light reactions: thylakoid membranes; photosystems I and II, photolysis of water (O2 released), non-cyclic photophosphorylation produces ATP and NADPH.
Calvin cycle (light-independent): stroma; CO2 fixed by RuBisCO onto RuBP, ATP and NADPH reduce to triose phosphate → glucose.
Limiting factors: light intensity, CO2 concentration, temperature affect photosynthesis rate; graphs plateau when another factor limits.
Enzyme kinetics: Michaelis–Menten, Vmax and Km (substrate concentration at ½ Vmax); rate increases with substrate until saturation; temperature and pH optima; inhibitors lower Vmax (non-competitive) or raise apparent Km (competitive).
Genetics: Mendelian inheritance, linkage, molecular genetics, mutations, gene expression
Mendel's laws: segregation (alleles separate in meiosis) and independent assortment (genes on different chromosomes assort independently). Monohybrid cross Aa × Aa → 3:1 phenotype, 1:2:1 genotype; test cross Aa × aa → 1:1.
Dihybrid cross AaBb × AaBb → 9:3:3:1 phenotype if genes unlinked.
Linkage: genes on the same chromosome tend to be inherited together; crossing over produces recombinants; recombination frequency <50% indicates linkage; 1% recombination ≈ 1 centimorgan.
Sex-linked inheritance: X-linked recessive disorders (e.g. haemophilia) affect males more; carrier females pass to sons.
DNA replication: semi-conservative; helicase unwinds, DNA polymerase adds complementary nucleotides 5'→3', leading (continuous) and lagging (Okazaki fragments) strands.
Transcription: DNA → mRNA by RNA polymerase in nucleus; translation: mRNA codons read by ribosomes with tRNA anticodons; start codon AUG (methionine), stop codons UAA, UAG, UGA; genetic code is degenerate and universal.
Mutations: point (substitution - missense, nonsense, silent), frameshift (insertion/deletion), chromosomal (deletion, duplication, inversion, translocation).
Gene regulation: operon model (lac operon inducible, trp operon repressible); in eukaryotes transcription factors, promoters, enhancers, epigenetic modifications.
Microorganisms, viruses, immunology and biotechnology
Bacteria: prokaryotes, shapes (coccus, bacillus, spirillum), peptidoglycan cell wall, binary fission, conjugation (plasmid transfer), endospores; nutrition autotrophic/heterotrophic.
Viruses: acellular obligate intracellular parasites; nucleic acid (DNA or RNA) + protein capsid, sometimes envelope; replicate only inside host cells; not affected by antibiotics.
Immunology innate: physical barriers (skin, mucous), inflammation, phagocytes, natural killer cells, complement.
Adaptive immunity: B lymphocytes → plasma cells secrete antibodies (humoral); T lymphocytes - helper T (CD4) activate, cytotoxic T (CD8) kill infected cells; memory cells give secondary response.
Antigen–antibody: specific binding, agglutination, neutralisation; primary vs secondary response; vaccines induce memory.
Biotechnology: recombinant DNA (restriction enzymes cut, DNA ligase joins, vectors/plasmids), PCR amplification, gel electrophoresis, gene cloning, transgenic organisms, CRISPR.
Applications: insulin production in bacteria, monoclonal antibodies, gene therapy, bioremediation; ethical and safety considerations.
Microorganisms in industry: fermentation (yeast - bread, beer; bacteria - yoghurt, cheese), antibiotics (Penicillium), sewage treatment.
Reproduction, heredity and evolution: reproduction in living organisms, evolutionary mechanisms
Asexual reproduction: mitosis-based, offspring genetically identical (binary fission, budding, fragmentation, vegetative propagation, parthenogenesis).
Sexual reproduction: meiosis + fertilisation → genetic variation; gametogenesis (spermatogenesis, oogenesis); hermaphroditism; external vs internal fertilisation.
Plant reproduction: alternation of generations (sporophyte/gametophyte); flower structure; pollination; double fertilisation in angiosperms → zygote + endosperm.
Animal reproduction: oestrous/menstrual cycles, hormonal control (FSH, LH, oestrogen, progesterone), embryonic development (cleavage, gastrulation, organogenesis), placenta in mammals.
Heredity: genotype vs phenotype; dominant/recessive; codominance and incomplete dominance; multiple alleles (ABO blood groups); polygenic traits; pedigree analysis.
Evolution evidence: fossil record, comparative anatomy (homologous/analogous structures), embryology, molecular (DNA/protein sequences), biogeography.
Mechanisms: natural selection (variation, differential survival, differential reproduction), mutation as source of variation, genetic drift (bottleneck, founder effect), gene flow, non-random mating.
Speciation: allopatric (geographic isolation) and sympatric; reproductive isolation (pre- and post-zygotic); Hardy–Weinberg equilibrium p² + 2pq + q² = 1, p + q = 1; changes indicate evolution.
Ecology and environment: ecosystems, population dynamics, biodiversity, human impact
Ecosystem components: biotope (abiotic: light, temperature, water, soil) + biocenosis (biotic: producers, consumers, decomposers); trophic levels and food webs; ~10% energy transfer between levels.
Biogeochemical cycles: carbon (photosynthesis, respiration, combustion, decomposition), nitrogen (fixation, nitrification, denitrification), water, phosphorus.
Population dynamics: exponential growth (J-curve) vs logistic growth (S-curve, carrying capacity K); factors: birth/death rates, immigration/emigration, density-dependent and density-independent factors.
Species interactions: predation, competition (intra/interspecific), mutualism, commensalism, parasitism, symbiosis.
Ecological succession: primary (bare substrate) and secondary (after disturbance); pioneer species → climax community.
Biodiversity: genetic, species, ecosystem levels; hotspots; threats - habitat loss, invasive species, pollution, overexploitation, climate change.
Human impact: greenhouse effect and climate change, acid rain, eutrophication, deforestation, desertification, ozone depletion; conservation strategies (protected areas, ex situ conservation, sustainable use).
Population ecology in humans: demographic transition, age pyramids, carrying capacity; sustainable development goals.