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| == Summary of Core Energy Metabolism lecture series == | | [[Image:BB-Bioblast.jpg|left|30px|link=http://www.bioblast.at/index.php/Bioblast:About|Bioblast wiki]] |
| | == Popular Bioblast page == |
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| [http://www.bioblast.at/index.php?title=Talk:MitoCom_Network&action=purge#Core_Energy_Metabolism_-_an_interactive_lecture_series|Core Energy Metabolism lecture series]
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| | == [[Bioblast alert]] [[Bioblast_alert_2013#Bioblast_alert_2013.2801.29:_2013-07-08|2013(01): 2013-07-08]] == |
| '''Core Energy Metabolism''' implies processes such as [[Respiration]] and [[Fermentation]], both of which are involved in [[ATP]] production.
| | ::::* MitoGlobal project: The '''[[Mitochondrial Global Network]] (MitoGlobal)''' initiates a joint publication to review the state-of-the-art terminology in the rapidly expanding field of mitochondrial respiratory physiology. From the [[MitoPedia: Respiratory states|present start]] there is a long way to go, and we invite experts in the field to a joint walk, asking for your suggestions - [mailto:erich.gnaiger@mitophysiology.org Email to Erich Gnaiger]. |
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| Respiration is the process of oxidative phosphorylation, where a chemisosmotic potential drives ATP synthesis.
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| Fermentation is the process of substrate-level phosphorylation, whereby ATP is derived from internally produced electron acceptors without a chemisomotic gradient.
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| Both processes are functionally related to maintain REDOX balance.
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| Whereas respiration involving burning of oxygen leads to profound heat production, fermentation is less effective due to lower enthropy.
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| In humans, in internal cell respiration, electrons are transferred from reduced Carbon substrates to the final electron acceptor oxygen.
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| Aerobic fermentation can proceed in the presence of oxygen. Negative effects of fermentation are acidification and energy deprivation.
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| Oxic and anoxic are terms to describe oxygen conditions in an environment.
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| Aerobic and anaerobic are terms used to refer to cell metabolism.
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| '''Chemisomotic coupling''' is one of the earliest events in single cells, i.e. bacteria, in evolution.
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| All single cells have a membrane-bound ATP-synthase.
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| ATP is produced by using gradients, whereby a chemisomotic potential is generated by Na- and proton pumps.
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| Protons are expelled into the cytosol, then move back into the intermembrane space. ATP is pulled out by [[ANT]].
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| '''LEAK''' vs. '''SLIP''' hypothesis | |
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| Electron transport can be partially uncoupled, loosely coupled, dyscoupled or uncoupled. Protons are pumped out of the matrix and outside compartment. Where is the LEAK and how does it take place against a gradient? Different hypotheses exist on the nature vs. the quantification of LEAK. Is it dependent on oxygen flux?
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| Whereas LEAK seems to be a property of the membrane, SLIP seems to be a property of the pump, continuing at high ATP concentrations.
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| Temperature occurs to influence these properties, as membrane fluidity is affected. Experiments at 25°C favor SLIP - experiments at 37°C favor LEAK.
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| Sports reserach experiments are done at 22°C, although they rather should be done at 40°C implying high heat production inside myocytes during exercise.
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| '''Coupling states'''
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| Understanding and evaluation of coupling states can give you information on organ or species differences, tissue injuries,...
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| CI, CII and CIV are pumps that pump protons out; uncouplers such as FCCP are protonophores, making protons flow back so that membrane potential eventually collapses. Every uncoupler also inhibits respiration at a certain concentration.
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| Substrates are actively transported across the mitochondrial membrane needing a gradient. Yeast mitochondria can also utilize cytosolic NADH, which is also produced in the TCA cycle, feeding electrons into the Q-junction via CI.
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| CI, CII & CIV as well as CII, CII & CIV are referred to as "membrane-bound Electron Transfer System" [[ETS]].
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| To find out what is limiting flux, you first have to take away any other limitations, e.g. substrates.
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| If submitochondrial particles are generated via e.g. sonication, the membrane structure disrupts and aligns spontaneously, possibly resulting in an inverted alignment, where NADH can be accessed from the outside, leading to a much larger ETS capacity.
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| Using the O2k, always the total ETS, incl. added substrates and transporters, is evaluated, which has to be differentiated from the membrane-bound ETS (pumps) that is mentioned in textbooks.
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| When looking at a coupling control protocol in intact cells [[Gnaiger 2008 POS]], at first, without any manipulation, cells respire according to their routine ATP demand - [[ROUTINE]].
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| [[File:IntactCells Gnaiger2008POS.JPG]]
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| By adding oligomycin, an inhibitor of ATP-synthase, a [[LEAK]] state is induced.
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| ATPase has 2 rotors. ATP has to be actively transported outside from the matrix space via AdenineNucleotideTranslocase ANT. ATP has a higher charge than ADP, and thus needs an electric gradient for transport.
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| Titrations of FCCP lead to an increase in respiration, reach a plateau (which is then marked as ETS, i.e. max. respiration) and then decrease respiration, due to inhibition. At ETS max. respiration, the high proton gradient does not have any feedback control on respiration.
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| Titrations of FCCP show the dynamics of respiration, giving rise to uncoupler kinetics.
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| FCCP, which is dissolved in Ethanol, can penetrate membranes. As more oxygen is dissolved in EtOH, O<sub>2</sub> concentrations might slightly increase after FCCP titrations.
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| By titration of ADP, OXPHOS capacity can be maximized. The proton gradient is utilized to phosphorylate ADP. To evaluate OXPHOS capacity, one needs saturating ADP concentrations, which ''in vivo'' may or may not occur. When ADP is saturating, no flux increase occurs.
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| ATPase can also be added experimentally, which then regenerates ADP, thereby imitating a ROUTINE state.
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| Adding an uncoupler in an ADP-stimulated maximum OXPHOS state, can tell you about the limitation of OXPHOS.
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| If the "PHOS capacity", i.e. the utilizator, is bigger that the ETS, then you are probably dealing with an experimental artefact, as this can not be the case.
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| The maximum P/e ratio can only be 1.
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| If it is smaller than one, then the phosphorylation system is limiting.
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