Anaerobic respiration

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Anaerobic respiration

Anaerobic respiration is the process of generating energy through cellular respiration (cellular respiration being the process in which organic molecules, generally glucose, are broken down by the body's cells in order to release energy for the use of the cell), without the use of oxygen.

bic respiration is defined as a membrane-bound biological process coupling the oxidation of electron donating substrates (e.g.

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Aerobic respiration in prokaryotes

Aerobic respiration is defined as a membrane-bound biological process coupling the oxidation of electron donating substrates (e.g. sugars and other organic compounds, but also inorganic molecules like hydrogen, sulfide/sulfur, ammonia, metals or metal ions) to the reduction of suitable external electron acceptors other than molecular oxygen. In contrast, in fermentation

Fermentation (biochemistry)

Fermentation is the process of deriving energy from the Redox of organic compounds, such as carbohydrates, using an Endogeny electron acceptor, which is usually an organic compound....
the oxidation of molecules is coupled to the reduction of an internally-generated electron acceptor, usually pyruvate. Hence, scientists who study prokaryotic physiology

Physiology

Physiology is the study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided between plant physiology and animal and all living things physiology but the principles of physiology are universal, no matter what particular organism is being studied....
view anaerobic respiration and fermentation as distinct processes and therefore do not use the terms interchangeably.

In aerobic respiration, as the electrons from the electron donor are transported down the electron transport chain

Electron transport chain

An electron transport chain couples a chemical reaction between an electron donor and an electron acceptor to the transfer of proton across a Cell membrane, through a set of mediating biochemical reactions....
to the terminal electron acceptor, protons are translocated over the cell membrane

Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
from "inside" to "outside", establishing a concentration gradient across the membrane which temporarily stores the energy released in the chemical reactions. This potential energy is then converted into ATP by the same enzyme used during aerobic respiration, ATP synthase

ATP synthase

An ATP synthase is a general term for an enzyme that can synthesize adenosine triphosphate from adenosine diphosphate and inorganic phosphate by using some form of energy....
. Possible electron acceptors for anaerobic respiration are nitrate, nitrite, nitrous oxide, oxidised amines and nitro-compounds, fumarate, oxidised metal ions, sulfate, sulfur, sulfoxo-compounds, halogenated organic compounds, selenate, arsenate, bicarbonate or carbon dioxide (in acetogenesis and methanogenesis).

In Plants

Equation:

C₆H₁₂O₆? 2CH₃CH₂OH + 2CO₂ + 118kJ of Energy

Examples of anaerobic respiration

glucose + 3NO₃^- + 3H₂O 6HCO₃^- + 3NH₄⁺, ?G⁰' = -1796 kJ

glucose + 3SO₄^2- + 3H⁺ 6HCO₃^- + 3SH^-, ?G⁰' = -453 kJ

glucose + 12S + 12H₂O 6HCO₃^- + 12HS^- + 18H⁺, ?G⁰' = -333 kJ

All of these terminal electron acceptors have larger reduction potential

Reduction potential

Reduction potential is the tendency of a chemical species to acquire electrons and thereby be redox. Each species has its own intrinsic reduction potential; the more positive the potential, the greater the species' affinity for electrons and tendency to be reduced....
s than O₂, meaning that less energy is released per oxidised molecule of primary electron donor

Electron donor

An electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process....
than in aerobic respiration (i.e. it is less energetically efficient). The ?G⁰' of aerobic respiration is -1234 kJ.

Fermentation is the process by which yeast cells carry out anaerobic respiration, producing ethanol and CO2 as a by-product. Example: wine grapes

Commercial applications of anaerobic respiration

Anaerobic digestion
Anaerobic digestion

Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is widely used to treat wastewater sludges and biodegradable waste because it provides volume and mass reduction of the input material....
Mechanical biological treatment
Mechanical biological treatment

A mechanical biological treatment system is a form of waste processing facility that combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion....