Galicia PAU Biology cheat sheet

Condensation forms glycosidic, ester and peptide bonds; hydrolysis reverses them.

Reducing-sugar test interpretation requires suitable assay conditions and controls; hydrolysis can change sucrose test results.

Cellulose = β-1,4 glucose, straight H-bonded microfibrils; starch and glycogen = α-glucose.

Triglyceride = glycerol + 3 fatty acids; phospholipid = phosphate head + 2 tails, amphipathic.

Enzymes lower activation energy; specificity comes from active-site shape.

Simple reversible competition increases apparent Km without changing Vmax; pure noncompetitive inhibition lowers Vmax without changing Km.

Prokaryotes lack a membrane-bound nucleus; bacterial peptidoglycan walls are not universal and archaeal walls differ.

Fluid mosaic membranes contain a lipid bilayer and proteins; sterol and carbohydrate composition depends on the cell.

Facilitated diffusion is passive; primary active transport may use ATP directly and secondary transport uses a gradient.

Water potential ψ = ψs + ψp; water moves from higher (less negative) to lower ψ.

Mitosis (P-M-A-T) after S-phase replication maintains chromosome number.

Cytokinesis: cleavage furrow in animals, cell plate in plants.

A–T has 2 hydrogen bonds, G–C has 3; strands are antiparallel with 3′–5′ phosphodiester bonds.

Semi-conservative replication: helicase, DNA polymerase (5′→3′), ligase on the lagging strand.

The standard code is triplet and degenerate, nearly universal; AUG is a common start codon with biological exceptions.

Meiosis I separates homologues; crossing over in prophase I produces recombinants.

A test cross is with a homozygous recessive to reveal an unknown genotype.

Informative linked-locus crosses often give excess parentals; recombination percentage approximates short map distances, not all intervals exactly.

En modelos simples: competitivo reversible aumenta Km aparente sin cambiar Vmax; no competitivo puro baja Vmax sin cambiar Km.

Glucólisis en el citosol: 2 ATP netos, 2 NADH y 2 piruvato por glucosa.

Krebs: por vuelta 3 NADH, 1 FADH₂, 1 ATP y 2 CO₂; dos vueltas por glucosa.

Cadena respiratoria: quimiosmosis, ATP sintasa y O₂ como aceptor final de electrones.

Fase luminosa produce ATP y NADPH; el O₂ viene de la fotólisis del agua.

Ciclo de Calvin: RuBisCO fija CO₂ y consume ATP y NADPH para sintetizar glúcidos.

Hypothesis = testable prediction; theory = broad supported explanation; law = consistent regularity.

Independent variable is manipulated; dependent is measured; controls are held constant.

Random assignment supports experimental causal inference; an observed association alone does not establish causation.

Accuracy = closeness to truth; precision = repeatability.

Replication and sample size reduce the influence of random chance.

Los virus son acelulares; los ciclos lítico y lisogénico son modelos de determinados bacteriófagos, no de todos los virus.

Retrovirus: retrotranscriptasa convierte ARN en ADN e integra el provirus.

Muchas bacterias tienen peptidoglicano; pared, plásmidos y otros rasgos deben comprobarse en cada organismo.

Linfocitos B → células plasmáticas → anticuerpos; CD4 ayudan y CD8 citotóxicos matan células infectadas.

La memoria adaptativa puede acelerar la respuesta; el predominio de IgG depende del contexto de la respuesta sistémica.

PCR: N0 por 2^n solo con duplicación ideal; en el mismo gel, ADN lineal pequeño suele migrar más lejos.

PCR copies a selected DNA region; ideal N0 times 2^n requires perfect doubling.

Positive, no-template and extraction controls test different potential failures.

DNA fragment length is not the same as nucleotide sequence identity.

Genomic DNA presence does not by itself establish gene expression.

A genetic change requires suitable evidence before its phenotype is inferred.