Cellular respiration

Cellular respiration is the process of oxidizing biological fuels using an inorganic electron acceptor, such as oxygen, to drive production of adenosine triphosphate (ATP), which contains energy.

Cellular respiration may be described as a set of metabolic reactions and processes that take place in the cells of organisms to transfer chemical energy from nutrients to ATP, and then release waste products.

Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity.

The products of this process are carbon dioxide and water, and the energy transferred is used to make bonds between ADP and a third phosphate group to form ATP (adenosine triphosphate), by substrate-level phosphorylation, NADH and FADH2.

[5] However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP per glucose.

They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation.

The PDC contains multiple copies of three enzymes and is located in the mitochondria of eukaryotic cells and in the cytosol of prokaryotes.

Isocitrate is modified to become α-ketoglutarate (5 carbons), succinyl-CoA, succinate, fumarate, malate and, finally, oxaloacetate.

[14] The net gain from one cycle is 3 NADH and 1 FADH2 as hydrogen (proton plus electron) carrying compounds and 1 high-energy GTP, which may subsequently be used to produce ATP.

It comprises the electron transport chain that establishes a proton gradient (chemiosmotic potential) across the boundary of the inner membrane by oxidizing the NADH produced from the Krebs cycle.

[15] The table below describes the reactions involved when one glucose molecule is fully oxidized into carbon dioxide.

When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis.

[19] Including one H+ for the transport reactions, this means that synthesis of one ATP requires 1 + 10/3 = 4.33 protons in yeast and 1 + 8/3 = 3.67 in vertebrates.

[20] The total ATP yield in ethanol or lactic acid fermentation is only 2 molecules coming from glycolysis, because pyruvate is not transferred to the mitochondrion and finally oxidized to the carbon dioxide (CO2), but reduced to ethanol or lactic acid in the cytoplasm.

The pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell.

This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate.

For multicellular organisms, during short bursts of strenuous activity, muscle cells use fermentation to supplement the ATP production from the slower aerobic respiration, so fermentation may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting.

Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor, such as oxygen, to produce large amounts of energy and drive the bulk production of ATP.

[21] Such organisms could be found in unusual places such as underwater caves or near hydrothermal vents at the bottom of the ocean.,[8]: 66–68  as well as in anoxic soils or sediment in wetland ecosystems.

In July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms which live 7900 feet (2400 meters) below the surface.

Typical eukaryotic cell
Out of the cytoplasm it goes into the Krebs cycle with the acetyl CoA. It then mixes with CO 2 and makes 2 ATP, NADH, and FADH. From there the NADH and FADH go into the NADH reductase, which produces the enzyme. The NADH pulls the enzyme's electrons to send through the electron transport chain. The electron transport chain pulls H + ions through the chain. From the electron transport chain, the released hydrogen ions make ADP for an result of 32 ATP. Lastly, ATP leaves through the ATP channel and out of the mitochondria.
Stoichiometry of aerobic respiration and most known fermentation types in eucaryotic cell. [ 17 ] Numbers in circles indicate counts of carbon atoms in molecules, C6 is glucose C 6 H 12 O 6 , C1 carbon dioxide CO 2 . Mitochondrial outer membrane is omitted.