anaerobic respiration

Examples of anaerobic respiration in the following topics:

• Electron Donors and Acceptors in Anaerobic Respiration

  • In anaerobic respiration, a molecule other than oxygen is used as the terminal electron acceptor in the electron transport chain.
  • Anaerobic respiration is the formation of ATP without oxygen.
  • Many different types of electron acceptors may be used for anaerobic respiration.
  • Organic compounds may also be used as electron acceptors in anaerobic respiration.
  • A molecule other than oxygen is used as the terminal electron acceptor in anaerobic respiration.

• Anaerobic Cellular Respiration

  • Some prokaryotes and eukaryotes use anaerobic respiration in which they can create energy for use in the absence of oxygen.
  • However, many organisms have developed strategies to carry out metabolism without oxygen, or can switch from aerobic to anaerobic cell respiration when oxygen is scarce.
  • Both methods are called anaerobic cellular respiration, where organisms convert energy for their use in the absence of oxygen.
  • Certain prokaryotes, including some species of bacteria and archaea, use anaerobic respiration.
  • Eukaryotes can also undergo anaerobic respiration.

• Slow-Twitch and Fast-Twitch Muscle Fibers

  • The ATP required for slow-twitch fibre contraction is generated through aerobic respiration (glycolysis and Krebs cycle) whereby 30 molecules of ATP are produced from each one of glucose in the presence of oxygen.
  • The reaction is slower than anaerobic respiration, which is why it is not suited to rapid movements, but much more efficient which is why slow-twitch muscles do not tire quickly.
  • Unlike slow-twitch fibers fast twitch-fibers rely on anaerobic respiration (glycolysis alone) to produce two molecules of ATP per molecule of glucose.
  • Whilst much less efficient than aerobic respiration it is not rate limited by a requirement for oxygen making it ideal for rapid bursts of movement.
  • A by-product of anaerobic respiration is lactate (lactic acid) which accumulates in the muscle tissue reducing the pH (making it more acidic, and producing the stinging feeling in muscles when exercising) which inhibits further anaerobic respiration.

• Proton Reduction

  • Anaerobic respiration utilizes highly reduced species - such as a proton gradient - to establish electrochemical membrane gradients.
  • This then drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen, or alternative receptors for anaerobic respiration.
  • Cellular respiration (both aerobic and anaerobic) utilizes highly reduced species such as NADH and FADH2 to establish an electrochemical gradient (often a proton gradient) across a membrane, resulting in an electrical potential or ion concentration difference across the membrane.
  • The reduced species are oxidized by a series of respiratory integral membrane proteins with sequentially increasing reduction potentials, the final electron acceptor being oxygen (in aerobic respiration) or another species (in anaerobic respiration).
  • Proton reduction is important for setting up electrochemical gradients for anaerobic respiration.

• Transforming Chemical Energy

  • Cellular respiration is the process of transforming chemical energy into forms usable by the cell or organism.
  • Respiration occurs within the cytoplasm of prokaryotes.
  • Several prokaryotes and a few eukaryotes use an inorganic molecule other than oxygen to drive the oxidation of their nutrients in a process called anaerobic respiration.
  • Electron acceptors for anaerobic respiration include nitrate, sulfate, carbon dioxide, and several metal ions.
  • The energy released during cellular respiration is then used in other biological processes.

• Nitrate Reduction and Denitrification

  • Denitrification is a type of anaerobic respiration that uses nitrate as an electron acceptor.
  • In anaerobic respiration, denitrification utilizes nitrate (NO3-) as a terminal electron acceptor in the respiratory electron transport chain.
  • Denitrification is a widely used process; many facultative anaerobes use denitrification because nitrate, like oxygen, has a high reduction potential
  • In general, it occurs where oxygen is depleted and bacteria respire nitrate as a substitute terminal electron acceptor.
  • When faced with a shortage of oxygen, some rhizobia species are able to switch from O2-respiration to using nitrates to support respiration.

• Syntrophy and Methanogenesis

  • Bacteria that perform anaerobic fermentation often partner with methanogenic archea bacteria to provide necessary products such as hydrogen.
  • A frequently cited example of syntrophy are methanogenic archaea bacteria and their partner bacteria that perform anaerobic fermentation.
  • Methanogenesis in microbes is a form of anaerobic respiration, performed by bacteria in the domain Archaea.
  • Unlike other microorganisms, methanogens do not use oxygen to respire; but rather oxygen inhibits the growth of methanogens.
  • Without methanogenesis, a great deal of carbon (in the form of fermentation products) would accumulate in anaerobic environments.

• Internal Respiration

  • Internal respiration refers to two distinct processes.
  • The oxygen supply for cellular respiration comes from the external respiration of the respiratory system.
  • The net formula for cellular respiration is:
  • Cellular respiration can occur anaerobically without oxygen, such as through lactic acid fermentation.
  • This process however is very inefficient compared to aerobic respiration, as without oxidative phosphorylation, the cell cannot produce nearly as much ATP (2 ATP compared to 38 during cellular respiration).

• Oxygen

  • Obligate aerobes require oxygen for aerobic cellular respiration.
  • In a process known as cellular respiration, these organisms use oxygen to oxidize substrates (for example sugars and fats) in order to obtain energy.
  • Facultative anaerobes can use oxygen, but also have anaerobic (i.e. not requiring oxygen) methods of energy production.
  • An anaerobic organism or anaerobe is any organism that does not require oxygen for growth.
  • And finally, facultative anaerobes, which can grow without oxygen but can utilize oxygen if it is present.

• Respiration and Proton Motive Force

  • Respiration is one of the key ways a cell gains useful energy to fuel cellular activity.
  • Respiration is one of the key ways a cell gains useful energy to fuel cellular activity .
  • Chemically, cellular respiration is considered an exothermic redox reaction.
  • Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism, which yields two molecules ATP per one molecule glucose.
  • Glycolysis takes place in the cytosol, does not require oxygen, and can therefore function under anaerobic conditions.