anaerobica

Anaerobica refers to conditions, organisms, or processes that occur in the absence of oxygen. The term is used across biology, ecology, medicine, and exercise science to distinguish activities that do not require oxygen from those that do.

Biological contexts distinguish obligate anaerobes, which cannot tolerate oxygen, from facultative anaerobes, which can use oxygen when it is present but continue to function anaerobically when it is not. Metabolism under anaerobic conditions occurs mainly through fermentation or anaerobic respiration. Fermentation produces energy by substrate-level phosphorylation and converts pyruvate into end products such as lactate in animals or ethanol and carbon dioxide in yeast and some bacteria. Anaerobic respiration uses inorganic compounds like nitrate or sulfate as terminal electron acceptors and can yield more energy than fermentation but less than aerobic respiration.

In exercise science, anaerobic activity refers to high‑intensity efforts that last for seconds to a few minutes and rely on energy systems that do not require immediate oxygen delivery, producing rapid but limited energy and often lactate accumulation. Training can increase anaerobic power and the lactate tolerance of muscles.

Industrial and environmental applications include anaerobic digestion, a microbial process that decomposes organic matter in oxygen-free conditions to produce biogas and a digestate used as fertilizer. In food production, anaerobic fermentation is used to produce products such as yogurt, cheese, beer, and wine. Understanding anaerobic processes also informs medical discussions of infections caused by obligate anaerobes.