Biology,
one step at a time.

Ribosomes translate mRNA into polypeptides. Ribosomes on rough endoplasmic reticulum commonly make proteins destined for secretion or membranes, allowing the growing polypeptide to enter the endoplasmic-reticulum lumen for folding and transport.

Watch for: Do not name a biological process without explaining the mechanism. For Cell structure, link the relevant structure or condition to the resulting effect.

On heating, a reducing sugar reduces blue copper(II) ions in Benedict's reagent to copper(I) oxide, producing an orange or brick-red precipitate at high concentration. The other observations correspond to tests for starch, protein and lipid.

Watch for: Do not name a biological process without explaining the mechanism. For Biological molecules, link the relevant structure or condition to the resulting effect.

A non-competitive inhibitor binds at a site other than the active site and reduces the activity of enzyme molecules. Increasing substrate cannot restore those molecules' catalytic activity, so Vmax falls while Km is unchanged in the idealised pure case.

Watch for: Do not name a biological process without explaining the mechanism. For Enzymes, link the relevant structure or condition to the resulting effect.

Cholesterol fits between phospholipid tails. It restricts excessive movement at high temperature, reduces close packing at low temperature and lowers permeability to some small water-soluble molecules, thereby stabilising membrane fluidity.

Watch for: Do not name a biological process without explaining the mechanism. For Cell membranes and transport, link the relevant structure or condition to the resulting effect.

Following accurate DNA replication, mitosis distributes one copy of each chromosome to each daughter nucleus. Repeated cell division therefore increases cell number without changing chromosome number or normally changing genotype.

Watch for: Do not name a biological process without explaining the mechanism. For The mitotic cell cycle, link the relevant structure or condition to the resulting effect.

RNA polymerase binds near a gene, uses the transcribed DNA strand as a template and joins complementary RNA nucleotides. The RNA sequence is complementary to the template and matches the non-transcribed strand except U replaces T.

Watch for: Do not name a biological process without explaining the mechanism. For Nucleic acids and protein synthesis, link the relevant structure or condition to the resulting effect.

Sieve tube elements have little cytoplasm and no nucleus at maturity. Adjacent companion cells have nuclei, many mitochondria and membrane transport proteins, providing metabolic support for active loading and unloading.

Watch for: Do not name a biological process without explaining the mechanism. For Transport in plants, link the relevant structure or condition to the resulting effect.

As ventricular muscle contracts, ventricular pressure exceeds atrial pressure. The pressure difference forces atrioventricular valves shut, preventing backflow into the atria; semilunar valves open once ventricular pressure exceeds arterial pressure.

Watch for: Do not name a biological process without explaining the mechanism. For Transport in mammals, link the relevant structure or condition to the resulting effect.

Respiring tissues load carbon dioxide into blood, so blood arriving at pulmonary capillaries has a higher carbon dioxide partial pressure than alveolar air. Carbon dioxide diffuses down this gradient across the thin barrier.

Watch for: Do not name a biological process without explaining the mechanism. For Gas exchange, link the relevant structure or condition to the resulting effect.

Finding infectious cases and completing an appropriate combination of antibiotics reduces the infectious reservoir and selection for resistance. Ventilation, reduced overcrowding, contact tracing and vaccination where used can further limit spread.

Watch for: Do not name a biological process without explaining the mechanism. For Infectious diseases, link the relevant structure or condition to the resulting effect.

When a large proportion of a population is immune, an infected person is less likely to contact a susceptible host. Transmission chains are interrupted, reducing pathogen prevalence and indirectly protecting some people who cannot be vaccinated.

Watch for: Do not name a biological process without explaining the mechanism. For Immunity, link the relevant structure or condition to the resulting effect.

Equal masses or numbers of organisms are equilibrated at controlled temperatures. Oxygen uptake per unit mass and time is measured, non-respiring controls account for pressure changes, and replicates support a mean and anomaly check.

Watch for: Do not name a biological process without explaining the mechanism. For Energy and respiration, link the relevant structure or condition to the resulting effect.

Light intensity is the independent variable; temperature, CO₂ availability and plant material should be controlled. After equilibration, oxygen volume or a calibrated probe gives a better rate than bubble size, and replicates permit a mean and anomaly check.

Watch for: Do not name a biological process without explaining the mechanism. For Photosynthesis, link the relevant structure or condition to the resulting effect.

The afferent arteriole is wider than the efferent arteriole, helping create high hydrostatic pressure. Water and small solutes cross fenestrated endothelium, basement membrane and podocyte filtration slits; cells and most proteins remain in blood.

Watch for: Do not name a biological process without explaining the mechanism. For Homeostasis, link the relevant structure or condition to the resulting effect.

Sodium channels inactivate while potassium channels open. K⁺ leaves, repolarising the membrane; slow closure can cause hyperpolarisation, and pumps plus diffusion restore the resting ion distribution during the refractory period.

Watch for: Do not name a biological process without explaining the mechanism. For Control and coordination, link the relevant structure or condition to the resulting effect.

Each bivalent can orient in either direction independently of other bivalents. Consequently, homologues assort into daughter cells in many combinations; random orientation of sister chromatids at metaphase II adds further variation after crossing over.

Watch for: Do not name a biological process without explaining the mechanism. For Inheritance, link the relevant structure or condition to the resulting effect.

Breeders use yield records and progeny performance to select parents with high genetic merit. Across generations, alleles associated with higher milk yield become more common, while management still affects the observed phenotype.

Watch for: Do not name a biological process without explaining the mechanism. For Selection and evolution, link the relevant structure or condition to the resulting effect.

Seed banks preserve plant seeds, while frozen zoos store gametes, embryos or tissues. These ex-situ resources retain alleles for future breeding or restoration, but functioning habitats and ecological interactions still require in-situ conservation.

Watch for: Do not name a biological process without explaining the mechanism. For Classification, biodiversity and conservation, link the relevant structure or condition to the resulting effect.

A pathogenic dominant HTT expansion strongly predicts future disease and can reveal information relevant to relatives. Consent, the right not to know, confidentiality, psychological support and possible discrimination are important considerations.

Watch for: Do not name a biological process without explaining the mechanism. For Genetic technology, link the relevant structure or condition to the resulting effect.

A scientific conclusion links relevant raw and processed evidence to the prediction, considers variability, anomalies and statistical results, and states the extent of support. A finite experiment supports or fails to support; it does not prove universally.

Watch for: Do not name a biological process without explaining the mechanism. For Practical, planning, analysis and evaluation skills, link the relevant structure or condition to the resulting effect.