Energy & Metabolism
30 mechanisms in this category
Adaptive Thermogenesis
A newborn rabbit exposed to 40°F cold activates brown fat immediately, producing a 5× heat increase, maintaining 98°F body temperature despite a 58°F...
Autophagy
When nutrients are scarce, cells transform from construction sites into recycling centers. This is autophagy - literally 'self-eating' - and it's one...
Behavioral Thermoregulation
Behavioral thermoregulation uses environmental positioning and movement to control body temperature. The Namib Desert beetle creates its own microclim...
Circadian Rhythms
Circadian rhythms are internal biological clocks that synchronize organisms to Earth's 24-hour rotation. In mammals, a master clock in the suprachiasm...
Countercurrent Heat Exchange
Countercurrent heat exchange occurs when arteries carrying warm blood run parallel to veins carrying cold blood, allowing heat to transfer between the...
Disposable Soma Theory
Proposed by Thomas Kirkwood (1977), disposable soma theory explains aging as an allocation strategy rather than a defect. Natural selection optimizes...
Ectothermy
Ectotherms (cold-blooded animals) regulate body temperature through external sources and behavioral thermoregulation. The desert iguana maintains 100°...
Endothermy
Endotherms (warm-blooded animals) maintain body temperature through metabolic heat generation. A hummingbird maintains 104°F body temperature with fly...
Entrainment
Entrainment is the process by which external cues (zeitgebers) synchronize internal biological rhythms to the environment. In mammals, light is the pr...
Freeze Tolerance
Freeze tolerance allows organisms to survive partial freezing by controlling where ice forms. The Wood Frog freezes solid in winter - 65% of body wate...
Gigantothermy
Gigantothermy is heat retention through large body size - low surface-to-volume ratio reduces heat loss. The 1,000-pound Leatherback Sea Turtle mainta...
Glycolysis
Glycolysis happens in the cytoplasm. It breaks glucose into pyruvate, producing a small amount of ATP quickly. This is the sprint metabolism - fast bu...
Hydraulic Limits
Above approximately 100-130 meters, water column tension in the xylem exceeds what the vascular system can sustain, causing cavitation (air bubbles th...
Jet Lag
Jet lag occurs when external time (local time zone) mismatches internal time (circadian rhythm). The SCN requires approximately 1 day per time zone to...
Kleiber's Law
In 1932, Swiss agricultural scientist Max Kleiber at UC Davis discovered that biology's most fundamental accounting doesn't follow intuition. Metaboli...
Krebs Cycle
The Krebs Cycle (or citric acid cycle) happens in mitochondria. It takes the pyruvate from glycolysis and completely oxidizes it, harvesting high-ener...
Metabolic Pathway Organization
Cellular metabolism is organized into modular pathways: sequences of reactions that convert starting substrates into end products through defined inte...
Nitrogen Fixation
Legumes and alders harbor symbiotic bacteria that convert atmospheric nitrogen to forms accessible to plants, enriching nitrogen-poor soils. Subsequen...
Non-Shivering Thermogenesis
Non-shivering thermogenesis generates heat through hormonal activation (thyroid, adrenaline) increasing cellular metabolism 50%. Every cell generates...
Oxidative Phosphorylation
Oxidative phosphorylation happens in the mitochondrial membrane. It uses those high-energy electrons to drive the production of most of your ATP - rou...
Regional Heterothermy
Regional heterothermy allows different body regions to operate at different temperatures. Bluefin tuna swim in 50°F water but maintain red muscle at 8...
Rete Mirabile
The rete mirabile (Latin: 'wonderful net') is a specialized blood vessel network that retains heat in specific body regions. In bluefin tuna, this net...
Shivering Thermogenesis
Shivering thermogenesis generates heat through involuntary muscle contractions at 10-20 Hz, producing 5× resting metabolic rate with 100% efficiency (...
Sirtuins
Every cell experiences 10,000 DNA lesions per day from oxidative damage, spontaneous depurination, and copying errors. Sirtuins are the repair crew -...
Social Thermogenesis
Social thermogenesis occurs when organisms cluster together for warmth. Naked mole rat colonies of 100+ cluster together, with members rotating from w...
Square-Cube Law
Galileo articulated it first in 1638: giant animals couldn't simply be scaled-up versions of small animals. The math is unforgiving. As organisms grow...
Supercooling
Supercooling prevents ice crystal formation despite sub-freezing temperatures by eliminating ice nucleation sites. The Arctic ground squirrel's body t...
Thermal Runaway
Thermal runaway is a physics term describing when heat generation accelerates faster than cooling mechanisms can compensate, leading to uncontrolled t...
Thermal Windows
Thermal windows are body structures with high surface area and minimal insulation that allow selective heat dissipation. The Toucan's bill (30-40% of...
Thermoregulation
Temperature regulation is the process by which organisms maintain optimal internal temperature despite external conditions. Every chemical reaction ha...