Galicia PAU General Sciences cheat sheet

Prokaryotic cells lack a nuclear envelope and membrane-bound organelles; their DNA is a single circular chromosome plus optional plasmids, and ribosomes are 70S (50S + 30S subunits), whereas eukaryotic cytoplasmic ribosomes are 80S (60S + 40S).

Mitochondrial ATP yield per glucose: glycolysis (cytosol) gives 2 ATP and 2 NADH; the pyruvate dehydrogenase link reaction and Krebs cycle give 2 ATP (GTP), 8 NADH and 2 FADH2; oxidative phosphorylation yields about 26-28 ATP, so the textbook total is roughly 30-32 ATP.

Mendelian test-cross ratios: monohybrid Aa x aa gives 1:1; dihybrid AaBb x aabb gives 1:1:1:1; selfing AaBb gives 9:3:3:1. Deviations indicate linkage, epistasis, or lethal genotypes.

Sex-linked recessive traits (e.g. haemophilia, red-green colour blindness) appear far more often in males because they carry one X chromosome; a carrier mother x unaffected father gives 50% of sons affected and 50% of daughters carriers.

DNA replication is semiconservative: helicase unwinds, primase lays RNA primers, DNA polymerase III extends 5' to 3' on the leading strand continuously and on the lagging strand as Okazaki fragments joined by ligase. Transcription uses RNA polymerase and uracil instead of thymine.

Human cardiac cycle at rest: about 0.8 s per beat (75 bpm), systole about 0.3 s and diastole about 0.5 s; cardiac output = heart rate x stroke volume, roughly 70 mL x 75 min-1 = about 5.25 L/min.

Nephron handling: glomerular filtration (ultrafiltration driven by blood pressure), then tubular reabsorption of glucose, amino acids and most water, then tubular secretion (H+, K+, drugs); ADH increases collecting-duct water permeability, aldosterone increases Na+ reabsorption.

Blood glucose regulation is antagonistic: beta cells of the islets of Langerhans secrete insulin (lowers glycaemia, promotes glycogen synthesis and cellular uptake), alpha cells secrete glucagon (raises glycaemia by glycogenolysis and gluconeogenesis).

Kinematics with constant acceleration: v = v0 + at, s = v0 t + at^2/2, v^2 = v0^2 + 2as. Free fall near Earth uses g = 9.8 m/s^2 downward; horizontal projectile motion separates constant-velocity x from uniformly accelerated y.

Newton's second law as a vector sum: sum F = ma. On an incline of angle theta the driving component is mg sin(theta) and the normal reaction is mg cos(theta); friction force magnitude is mu N.

Energy and momentum: Ek = mv^2/2, Ep (gravitational near surface) = mgh, elastic = kx^2/2, work W = F d cos(theta). Momentum p = mv is conserved in collisions; kinetic energy is conserved only in elastic ones.

Uniform circular motion: angular velocity omega = 2 pi/T, linear speed v = omega r, centripetal acceleration a = v^2/r = omega^2 r, centripetal force F = mv^2/r. Gravitational field g = GM/r^2 outside a spherical mass.

Simple harmonic motion: restoring force F = -kx, period of a mass-spring system T = 2 pi sqrt(m/k), period of a pendulum T = 2 pi sqrt(L/g); period is independent of amplitude for small oscillations.

Waves: v = lambda f, period T = 1/f. Snell's law n1 sin(theta1) = n2 sin(theta2) with n = c/v; total internal reflection occurs beyond the critical angle sin(theta_c) = n2/n1 when n1 > n2.

Electric circuits: Ohm's law V = IR, power P = VI = I^2 R = V^2/R. Resistors in series add; in parallel 1/R = sum 1/Ri. Kirchhoff's rules: node currents sum to zero, and loop voltage drops sum to zero.

Electromagnetic induction and fields: Faraday's law emf = -d(Phi)/dt with flux Phi = B A cos(theta), Lenz's law fixes the induced current direction opposing the change; force on a current-carrying wire F = B I L sin(theta).

Mole relations: n = m/M, n = N/N_A (N_A = 6.022e23 mol-1), molar gas volume at STP (273 K, 1 atm) is 22.4 L. Concentration c = n/V in mol/L; dilution satisfies c1 V1 = c2 V2.

Electron configuration follows Aufbau, Pauli and Hund rules; orbital order 1s 2s 2p 3s 3p 4s 3d. Periodicity: atomic radius decreases across a period and increases down a group; ionisation energy and electronegativity rise across a period.

Bond type decision rule: metal + non-metal gives ionic; two non-metals give covalent (polar if electronegativity difference is roughly 0.4-1.7); metallic bonding in metals. VSEPR predicts geometry: 2 pairs linear, 3 trigonal planar, 4 tetrahedral, 4 with one lone pair trigonal pyramidal.

Acid-base definitions: Arrhenius (H+ in water), Bronsted-Lowry (proton donor/acceptor), Lewis (electron-pair acceptor/donor). pH = -log[H3O+], pOH = -log[OH-], pH + pOH = 14 at 25 C; strong acid/base fully dissociates, weak ones obey Ka or Kb.

Equilibrium and Le Chatelier: Kc for aA + bB <=> cC + dD is [C]^c[D]^d/([A]^a[B]^b). Raising pressure shifts toward fewer gas moles, raising temperature shifts in the endothermic direction, and a catalyst changes only the rate, not K or the position.

Redox and electrochemistry: oxidation is loss of electrons, reduction is gain. In a galvanic cell the anode (oxidation) is negative, the cathode (reduction) is positive, and cell emf E = E(cathode) - E(anode) from standard reduction potentials.

Thermochemistry: enthalpy change of reaction = sum bond enthalpies broken - sum bond enthalpies formed; Hess's law allows adding stepwise enthalpies. Exothermic reactions have negative delta H; bond formation releases energy.

Organic functional groups and isomerism: alkanes (C-C), alkenes (C=C), alcohols (-OH), aldehydes (-CHO), ketones (C=O between carbons), carboxylic acids (-COOH), esters (-COO-), amines (-NH2). Isomers may be chain, positional, functional or geometric (cis/trans about a C=C).

Earth's layered structure by composition: crust (oceanic basaltic, about 5-10 km; continental granitic, up to about 70 km), mantle (peridotite, to 2900 km depth) and core (iron-nickel, outer liquid, inner solid). The Mohorovicic discontinuity separates crust from mantle.

Plate tectonics: divergent boundaries (mid-ocean ridges, rifts) create new lithosphere with shallow earthquakes; convergent boundaries give subduction zones with deep earthquakes, volcanic arcs and trenches, or continental collision belts; transform boundaries give strike-slip faults such as the San Andreas.

Seismic waves: P waves are longitudinal and fastest, travel through solids and liquids; S waves are transverse, slower, and cannot pass liquids, which proves the outer core is liquid. Epicentre is the surface point above the focus; the S-P interval estimates distance to the epicentre.

Rock cycle classification: igneous (plutonic coarse-grained, volcanic fine-grained), sedimentary (detrital, chemical, organic; strata, fossils) and metamorphic (foliation and recrystallisation under heat and pressure, e.g. limestone to marble, shale to slate).

Relative dating principles: superposition, original horizontality, lateral continuity, cross-cutting relationships and faunal succession. An unconformity marks a gap in the record; index fossils give narrow time ranges for correlation.

Geological time: Precambrian about 4600-541 Ma, Palaeozoic 541-252 Ma ending with the Permian-Triassic extinction, Mesozoic 252-66 Ma ending with the Cretaceous-Palaeogene extinction, Cenozoic 66 Ma to present including the Quaternary glaciations.

Weathering and erosion: physical (freeze-thaw, thermal, salt), chemical (hydrolysis, carbonation of limestone, oxidation) and biological. Karst landscapes form by carbonation of limestone; river profiles show V-shaped valleys upstream and meanders and floodplains downstream.

Galicia-specific geology: the Hercynian (Variscan) orogeny produced the granitic and metamorphic basement of the Iberian Massif; Galicia lies at the boundary of the Eurasian and African plates, with NW-SE faults and the Galicia Interior Basin offshore; coastal rias are drowned river valleys formed during post-glacial sea-level rise.

Hypothesis-testing structure: observation, question, hypothesis, prediction, controlled experiment, data analysis, conclusion, communication. A hypothesis must be falsifiable; a theory is a well-tested explanatory framework, not a guess.

Variable control: the independent variable is manipulated, the dependent variable is measured, and controlled variables are held constant. A control group receives no treatment or a placebo; randomisation and blinding reduce bias.

Measurement quality: accuracy is closeness to the true value, precision is reproducibility of repeated measurements. Random errors scatter and are reduced by averaging; systematic errors shift all readings and require calibration or correction.

Error propagation and reporting: absolute uncertainty of a sum or difference adds absolute uncertainties; for products and quotients relative uncertainties add. Result written as value +/- uncertainty with consistent significant figures.

Graphing rules: independent variable on the x-axis, dependent on the y-axis, labelled axes with units, appropriate scale, best-fit line. A linearised graph (e.g. T^2 versus L for a pendulum) tests proportionality through the slope.

Laboratory safety and technique: goggles and lab coat, fume hood for volatile reagents, acid added to water (never water to acid), pipette never by mouth, waste segregated. Read meniscus at eye level; burette readings to 0.05 mL.

Standard separation and analysis techniques: filtration (insoluble solid), decantation, centrifugation, distillation (boiling-point difference), chromatography (differential adsorption), and spectroscopy or titration for quantitative determination.

Data interpretation and ethics: distinguish correlation from causation, identify outliers and state limitations, cite sources, avoid fabrication or plagiarism, and report results including those that contradict the hypothesis.