Reference

Glossary

Plain-language definitions for the biology and chemistry terms you’ll encounter on Virisource. Every entry links to its source — mostly Wikipedia. We aggregate definitions; we don’t rewrite them.

AMPKAMP-activated protein kinase: An enzyme that acts as a cellular energy sensor: when cellular ATP falls and AMP rises, AMPK switches on catabolic (energy-generating) pathways and shuts down anabolic (energy-consuming) ones. Activation of AMPK is associated with improved metabolic health, insulin sensitivity, and autophagy induction.
Antioxidant: A molecule that neutralizes reactive oxygen species (ROS) directly or by triggering cellular antioxidant defense pathways. Dietary antioxidants include polyphenols, carotenoids, and vitamins C and E. Mechanisms often involve gene-signaling (e.g., activating Nrf2) rather than direct chemical scavenging.
Autophagy: A cellular "recycling" process in which damaged proteins, organelles, and aggregates are packaged into vesicles and delivered to lysosomes for degradation. Induced by fasting, caloric restriction, exercise, and specific compounds like spermidine; considered a core longevity mechanism.
Carotenoid: A class of red, orange, and yellow lipid-soluble pigments made by plants, algae, and some bacteria. Examples include lycopene (tomatoes), beta-carotene (carrots), and astaxanthin (algae, salmon). Several have antioxidant and light-protective roles in human tissues.
Epigenetics: Heritable or stable changes in gene expression that do not alter the DNA sequence itself — including DNA methylation, histone modification, and non-coding RNA. Epigenetic patterns shift with age and form the basis of several "biological age" clocks.
Flavonoid: A large group of plant polyphenols with characteristic ring structures, including flavones, flavanols, anthocyanins, and isoflavones. Found widely in berries, tea, citrus, cocoa, and vegetables; studied for cardiovascular and cognitive effects.
Glycation: The non-enzymatic attachment of a sugar to a protein or lipid, forming advanced glycation end-products (AGEs) that stiffen tissues and impair signaling. Elevated glycation is associated with aging, diabetes, and cardiovascular disease.
Isothiocyanate: A class of sulfur-containing compounds released when glucosinolates in cruciferous vegetables (broccoli, kale, cabbage, broccoli sprouts) are chewed or chopped. Sulforaphane is the best-known example; activates the Nrf2 antioxidant pathway.
Methylation: The transfer of a methyl group (CH₃) to DNA, RNA, proteins, or small metabolites. DNA methylation regulates gene expression and homocysteine clearance; methylation patterns change with age and underlie biological-age clocks like the Horvath clock.
Mitochondrial biogenesis: The process by which cells make new mitochondria, typically in response to increased energy demand, exercise, or caloric restriction. PGC-1α is the master regulator. Declining biogenesis is considered a hallmark of aging.
Mitophagy: A selective form of autophagy that targets damaged or dysfunctional mitochondria for degradation. Essential for maintaining a healthy mitochondrial pool; impaired mitophagy is associated with neurodegeneration and aging.
mTORMechanistic Target of Rapamycin: A protein kinase that integrates nutrient and growth signals to regulate cell growth, protein synthesis, and metabolism. Chronic mTOR activation inhibits autophagy; its pharmacological inhibition (e.g., by rapamycin) extends lifespan in yeast, worms, flies, and mice.
NAD⁺Nicotinamide adenine dinucleotide: A coenzyme essential for redox reactions in metabolism and a required substrate for sirtuins, PARPs, and CD38. Tissue NAD⁺ levels decline with age. Dietary precursors include nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN).
Nrf2Nuclear factor erythroid 2–related factor 2: A transcription factor that regulates hundreds of antioxidant and detoxification genes. Activation by compounds such as sulforaphane increases cellular resistance to oxidative and electrophilic stress.
Oxidative stress: An imbalance between reactive oxygen species (ROS) production and the cell’s ability to detoxify them. Chronic oxidative stress damages DNA, proteins, and membranes and is implicated in many age-related diseases.
Polyamine: A family of small organic compounds (spermidine, spermine, putrescine) with multiple amino groups. Polyamines are involved in cell growth, DNA stability, and autophagy induction. Dietary sources include wheat germ, aged cheese, mushrooms, and natto.
Polyphenol: A broad category of plant secondary metabolites with multiple phenol rings, including flavonoids, stilbenes, lignans, and tannins. Found in tea, coffee, berries, olive oil, and red wine. Studied for cardiovascular, metabolic, and longevity effects.
Senolytic: A compound that selectively induces death in senescent cells — cells that have permanently stopped dividing but remain metabolically active and secrete pro-inflammatory factors (the senescence-associated secretory phenotype, or SASP). Senescent-cell burden rises with age; fisetin and quercetin are the best-studied food-sourced senolytic candidates.
Sirtuin: A family of NAD⁺-dependent protein deacetylases (SIRT1–SIRT7) that regulate metabolism, DNA repair, and stress response. Activation of sirtuins is a leading hypothesis for how caloric restriction extends lifespan.
Telomere: Repetitive DNA sequences that cap the ends of linear chromosomes, protecting them from deterioration. Telomeres shorten with each cell division; critically short telomeres trigger senescence or apoptosis. Telomere attrition is a hallmark of aging.

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