Foundations

The mammalian urea cycle combines nitrogen from ammonia and aspartate with bicarbonate-derived carbon to form urea.

De novo purine synthesis builds a ring on activated ribose toward IMP, then branches toward AMP and GMP.

In the stated reversible single-substrate Michaelis–Menten model, competitive inhibition increases apparent Km while leaving Vmax unchanged.

Metabolic flux responds to substrate/product availability, allosteric effectors, covalent enzyme modification and cellular demand.

For an autosomal diploid two-allele locus, random union of gametes with frequencies p and q gives genotype proportions p², 2pq and q².

The neutral diploid Wright–Fisher model samples 2N gene copies independently from the previous generation.

In a specified population model, narrow-sense heritability is the ratio of additive genetic variance to phenotypic variance.

Likelihood phylogenetics compares how probable an aligned sequence dataset is under candidate trees, branch lengths and substitution models.

Magnification enlarges an image; resolution determines whether adjacent structures can be distinguished.

PCR repeatedly separates template DNA, anneals sequence-directed primers and extends them with a suitable DNA polymerase.

Molecular cloning inserts a selected DNA fragment into a replicating vector for propagation or study.

Sanger sequencing detects terminated DNA products produced when extension incorporates a nucleotide lacking the required 3′ hydroxyl.

SDS-PAGE uses denaturing detergent treatment to separate suitable proteins primarily by apparent size.

A biological experiment tests a stated hypothesis using measured outcomes and comparisons that address alternative explanations.

Bacteria and archaea have distinct cell-envelope and molecular organizations despite both lacking a membrane-enclosed nucleus.

Phototrophy and chemotrophy describe energy sources; lithotrophy and organotrophy describe electron donors; autotrophy and heterotrophy describe carbon sources.

Viruses depend on host-cell systems for replication.

Fungi are eukaryotic absorptive heterotrophs that secrete enzymes and take up released nutrients.

Protist is a convenient description for diverse eukaryotes outside the familiar animal, plant and fungal categories rather than one natural monophyletic group.

Plant meristems supply dividing cells for growth; apical and lateral meristems contribute to length and girth in the stated vascular-plant model.

Plant growth responds to interacting chemical and environmental signals.

In the sexual seed-plant life cycle, reduced gametophytes participate in pollen-mediated reproduction and ovules develop into seeds following the appropriate fertilization sequence.

Epithelial, connective, muscle and nervous tissues contribute different structural and functional roles in animal organs.

In the neuronal model, voltage-dependent ion conductances create regenerative action potentials followed by refractory behaviour.

Animal embryogenesis includes division of the zygote, tissue rearrangement and differentiation.

Community composition depends on interactions and environmental conditions.

A food web represents multiple feeding connections, including detrital pathways.

Nitrogen fixation converts N₂ toward biologically usable reduced nitrogen; ammonification, nitrification and denitrification transform nitrogen among distinct chemical pools.

Biodiversity includes genetic, species and ecosystem dimensions.

Stress describes force per area on a specified plane; strain describes deformation.