Search by property

Property "Has-20abstract" (as page type) with input value "We-20have-20seen-20that-20there-20is-20no-20simple-20answer-20to-20the-20question-20'what-20controls-20respiration-3F'-20The-20answer-20varies-20with-20(a)-20the-20size-20of-20the-20system-20examined-20(mitochondria,-20cell-20or-20organ),-20(b)-20the-20conditions-20(rate-20of-20ATP-20use,-20level-20of-20hormonal-20stimulation),-20and-20(c)-20the-20particular-20organ-20examined.-20Of-20the-20various-20theories-20of-20control-20of-20respiration-20outlined-20in-20the-20introduction-20the-20ideas-20of-20Chance-20-26-20Williams-20(1955,-201956)-20give-20the-20basic-20mechanism-20of-20how-20respiration-20is-20regulated.-20Increased-20ATP-20usage-20can-20cause-20increased-20respiration-20and-20ATP-20synthesis-20by-20mass-20action-20in-20all-20the-20main-20tissues.-20Superimposed-20on-20this-20basic-20mechanism-20is-20calcium-20control-20of-20matrix-20dehydrogenases-20(at-20least-20in-20heart-20and-20liver),-20and-20possibly-20also-20of-20the-20respiratory-20chain-20(at-20least-20in-20liver)-20and-20ATP-20synthase-20(at-20least-20in-20heart).-20In-20many-20tissues-20calcium-20also-20stimulates-20ATP-20usage-20directly-3B-20thus-20calcium-20may-20stimulate-20energy-20metabolism-20at-20(at-20least)-20four-20possible-20sites,-20the-20importance-20of-20each-20regulation-20varying-20with-20tissue.-20Regulation-20of-20multiple-20sites-20may-20occur-20(from-20a-20teleological-20point-20of-20view)-20because:-20(a)-20energy-20metabolism-20is-20branched-20and-20thus-20proportionate-20regulation-20of-20branches-20is-20required-20in-20order-20to-20maintain-20constant-20fluxes-20to-20branches-20(e.g.-20to-20proton-20leak-20or-20different-20ATP-20uses)-3B-20and-2For-20(b)-20control-20over-20fluxes-20is-20shared-20by-20a-20number-20of-20reactions,-20so-20that-20large-20increases-20in-20flux-20requires-20stimulation-20at-20multiple-20sites-20because-20each-20site-20has-20relatively-20little-20control.-20Control-20may-20be-20distributed-20throughout-20energy-20metabolism,-20possibly-20due-20to-20the-20necessity-20of-20minimizing-20cell-20protein-20levels-20(see-20Brown,-201991).-20The-20idea-20that-20energy-20metabolism-20is-20regulated-20by-20energy-20charge-20(as-20proposed-20by-20Atkinson,-201968,-201977)-20is-20misleading-20in-20mammals.-20Neither-20mitochondrial-20ATP-20synthesis-20nor-20cellular-20ATP-20usage-20is-20a-20unique-20function-20of-20energy-20charge-20as-20AMP-20is-20not-20a-20significant-20regulator-20(see-20for-20example-20Erecinska-20et-20al.,-201977).-20The-20near-2Dequilibrium-20hypothesis-20of-20Klingenberg-20(1961)-20and-20Erecinska-20-26-20Wilson-20(1982)-20is-20partially-20correct-20in-20that-20oxidative-20phosphorylation-20is-20often-20close-20to-20equilibrium-20(apart-20from-20cytochrome-20oxidase)-20and-20as-20a-20consequence-20respiration-20and-20ATP-20synthesis-20are-20mainly-20regulated-20by-20(a)-20the-20phosphorylation-20potential,-20and-20(b)-20the-20NADH-2FNAD+-20ratio.-20However,-20oxidative-20phosphorylation-20is-20not-20always-20close-20to-20equilibrium,-20at-20least-20in-20isolated-20mitochondria,-20and-20relative-20proximity-20to-20equilibrium-20does-20not-20prevent-20the-20respiratory-20chain,-20the-20proton-20leak,-20the-20ATP-20synthase-20and-20ANC-20having-20significant-20control-20over-20the-20fluxes.-20Thus-20in-20some-20conditions-20respiration-20rate-20correlates-20better-20with-20-5BADP-5D-20than-20with-20phosphorylation-20potential,-20and-20may-20be-20relatively-20insensitive-20to-20mitochondrial-20NADH-2FNAD+-20ratio." contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.

Showing below up to 0 results starting with #1.

View (previous 50 | next 50) (20 | 50 | 100 | 250 | 500)