aerobic respiration

Examples of aerobic respiration in the following topics:

• Pyruvic Acid and Metabolism

  • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration); when oxygen is lacking, it ferments to produce lactic acid.
  • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactic acid when oxygen is lacking (fermentation).

• Oxygen

  • An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.
  • Several varietis of aerobes exist .
  • 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.
  • Aerobically different bacteria behave differently when grown in liquid culture: 1) Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. 2) Obligate anaerobic bacteria gather at the bottom to avoid oxygen. 3) Facultative bacteria gather mostly at the top, since aerobic respiration is advantageous (ie, energetically favorable); but as lack of oxygen does not hurt them, they can be found all along the test tube. 4) Microaerophiles gather at the upper part of the test tube but not at the top.

• Fermentation Without Substrate-Level Phosphorylation

  • In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen, via an electron transport chain.
  • The antibiotic activity of Hops also inhibits aerobic metabolism in Yeast.
  • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactic acid when oxygen is lacking (fermentation).

• Proton Reduction

  • Anaerobic respiration utilizes highly reduced species - such as a proton gradient - to establish electrochemical membrane gradients.
  • The reverse reaction, respiration, oxidizes sugars (loses an electron) to produce carbon dioxide and water.
  • 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.

• Sulfate and Sulfur Reduction

  • Sulfate reduction is a type of anaerobic respiration that utilizes sulfate as a terminal electron acceptor in the electron transport chain.
  • Sulfate reduction is a type of anaerobic respiration that utilizes sulfate as a terminal electron acceptor in the electron transport chain.
  • Compared to aerobic respiration, sulfate reduction is a relatively energetically poor process, though it is a vital mechanism for bacteria and archaea living in oxygen-depleted, sulfate-rich environments.
  • The hydrogen produced during fermentation is actually what drives respiration during sulfate reduction.

• The Energetics of Chemolithotrophy

  • ., carbon dioxide fixation) or energy conservation via aerobic or anaerobic respiration.
  • The electron acceptor can be oxygen (in aerobic bacteria), but a variety of other electron acceptors, organic and inorganic, are also used by various species.

• Respiration and Proton Motive Force

  • 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 reactions require oxygen for ATP generation.
  • During aerobic conditions, the pyruvate enters the mitochondrion to be fully oxidized by the Krebs cycle.
  • Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism, which yields two molecules ATP per one molecule glucose.

• Electron Donors and Acceptors in Anaerobic Respiration

  • Anaerobic respiration is the formation of ATP without oxygen.
  • These molecules have a lower reduction potential than oxygen; thus, less energy is formed per molecule of glucose in anaerobic versus aerobic conditions.
  • 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.

• Gas Requirements

  • Often, they respire oxygen as rapidly as it is supplied, keeping the amount of free oxygen low. 3) Aerobes that require oxygen to grow, yet their nitrogenase is still debilitated if exposed to oxygen. 4) Oxygenic photosynthetic bacteria generate oxygen as a by-product of photosynthesis, yet some are able to fix nitrogen as well. 5) And finally, Anoxygenic photosynthetic bacteria that do not generate oxygen during photosynthesis as they have only a single photosystem which cannot split water.

• Iron Oxidation

  • Under aerobic, moderate pH conditions ferrous iron is oxidized spontaneously to the ferric (Fe3+) form and is hydrolyzed abiotically to insoluble ferric hydroxide (Fe(OH)3).
  • Biochemically, aerobic iron oxidation is a very energetically poor process which therefore requires large amounts of iron to be oxidized by the enzyme rusticyanin to facilitate the formation of proton motive force.
  • Although ferric iron is the most prevalent inorganic electron acceptor, a number of organisms (including the iron-reducing bacteria mentioned above) can use other inorganic ions in anaerobic respiration.