Cameroon GCE O-Level 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.

Negative feedback reverses a deviation; positive feedback amplifies and must terminate.

Surface area to volume ratio drives the need for specialized exchange surfaces.

Pulmonary arteries carry deoxygenated blood away from the heart.

Xylem moves water up (cohesion–tension); phloem moves sugars by pressure flow.

Insulin lowers blood glucose; glucagon raises it - both are negative feedback.

Selection, mutation, gene flow, and drift are the mechanisms of allele frequency change.

Hardy-Weinberg is an idealized null model; q squared gives recessive phenotype frequency only under the stated two-allele dominance and penetrance assumptions.

p + q = 1 and p² + 2pq + q² = 1; heterozygotes are 2pq.

Homologous structures reflect ancestry; analogous structures reflect convergent evolution.

Allopatric speciation can follow geographic isolation; prezygotic barriers act before fertilization.

Water potential includes solute and pressure effects.

Xylem flow is explained through water-potential gradients and cohesion-tension.

Phloem follows source-sink organization, not a universal downward direction.

Loading mechanisms and stomatal timing can vary among plant species.

Stomatal closure trades reduced water loss against carbon-dioxide access.

Ruhepotential beruht auf K⁺-Leckkanälen und der Na⁺/K⁺-ATPase (3 Na⁺ raus, 2 K⁺ rein).

Aktionspotentiale folgen unter gleichen Bedingungen dem Alles-oder-nichts-Prinzip; Frequenz, Zeitpunkt und Populationsaktivität können Information tragen.

Myelinisierung beschleunigt die Leitung durch saltatorische Erregung.

EPSP und IPSP werden am Axonhügel summiert; erst das Summensignal entscheidet über ein Aktionspotential.

Licht hyperpolarisiert den Fotorezeptor und senkt die Glutamatfreisetzung.

Gifte immer einer Ebene zuordnen: Freisetzung, Rezeptor, Abbau oder Weiterleitung.

Logistic growth includes carrying capacity K; exponential growth does not.

Energy flows through ecosystems; 10 percent trophic transfer is an illustrative approximation, not a universal efficiency.

Most organisms require fixed nitrogen; phosphorus lacks a major atmospheric reservoir in the standard school-cycle model.

Mark–recapture: N = (marked first × total second) ÷ marked second.

Primary succession starts on bare rock; secondary succession starts where soil remains.