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Anaerobic cellular respiration and fermentation generate ATP in very different ways, and the terms should not be treated as synonyms. Cellular respiration (both aerobic and anaerobic) uses highly reduced chemical compounds such as NADH and FADH 2 (for example produced during glycolysis and the citric acid cycle) to establish an electrochemical gradient (often a proton gradient) across a membrane.
Anaerobic respiration is used by microorganisms, either bacteria or archaea, in which neither oxygen (aerobic respiration) nor pyruvate derivatives (fermentation) is the final electron acceptor. Rather, an inorganic acceptor such as sulfate ( SO 2− 4 ), nitrate ( NO − 3 ), or sulfur (S) is used. [ 16 ]
Cellular waste products are formed as a by-product of cellular respiration, a series of processes and reactions that generate energy for the cell, in the form of ATP. One example of cellular respiration creating cellular waste products are aerobic respiration and anaerobic respiration. Each pathway generates different waste products.
As dissimilatory nitrate reduction to ammonium is an anaerobic respiration process, marine microorganisms capable of performing DNRA are most commonly found in environments low in O 2, such as oxygen minimum zones (OMZs) in the water column, or sediments with steep O 2 gradients. [11] [12] The oceanic nitrogen cycle with the role of DNRA.
Typically, the complete breakdown of one molecule of glucose by aerobic respiration (i.e. involving glycolysis, the citric-acid cycle and oxidative phosphorylation, the last providing the most energy) is usually about 30–32 molecules of ATP. [16] Oxidation of one gram of carbohydrate yields approximately 4 kcal of energy. [3]
Methanogenesis is the final step in the anaerobic decay of organic matter. During the decay process, electron acceptors (such as oxygen , ferric iron , sulfate , and nitrate ) become depleted, while hydrogen (H 2 ) and carbon dioxide accumulate.
The energy yield of anaerobic respiration and fermentation (i.e. the number of ATP molecules generated) is less than in aerobic respiration. [8] This is why facultative anaerobes, which can metabolise energy both aerobically and anaerobically, preferentially metabolise energy aerobically.
Dissimilatory metal-reducing microorganisms are a group of microorganisms (both bacteria and archaea) that can perform anaerobic respiration utilizing a metal as terminal electron acceptor rather than molecular oxygen (O 2), which is the terminal electron acceptor reduced to water (H 2 O) in aerobic respiration. [1]