Level flow

From Bioblast
Jump to: navigation, search
Bioblasts - Richard Altmann and MiPArt by Odra Noel
MitoPedia     Terms and abbreviations     Preprints and history     MiP and biochemistry     Concepts and methods     MitoPedia: SUIT     MitoPedia: O2k


Level flow


E.jpg Level flow is a steady state of a system with an input process coupled to an output process (coupled system), in which the output force is zero. Clearly, energy must be expended to maintain level flow, even though output is zero (Caplan and Essig 1983; referring to zero output force, while output flow may be maximum).

Abbreviation: E

Communicated by Gnaiger E 2011-02-27, edited 2014-04-23.

Level flow and State 3

Level flow in mitochondrial respiration can define:
(i) A state of (incompletely) coupled respiration at zero (minimum) phosphorylation potential (and saturating ADP and Pi) supported by an excess of defined reduced substrates, which is OXPHOS capacity, P, at minimum levels of ATP (to maintain the output force or Gibbs force of phosphorylation near zero);
(ii) A state of noncoupled respiration at low mt-membrane potential supported by an excess of defined reduced substrates, which is ET capacity, E, defining the collapsed protonmotive force as (near-zero) output force (independent of ADP and ATP concentrations and the corresponding value of the Gibbs force of phosphorylation).
Since E may be higher or equal to P, level flow does not sufficiently define a mitochondrial respiratory state, but refers only to the general boundary conditions of a low ouput force. State 3 is a state of ‘high ADP’ (Chance and Williams 1955), without restriction to ‘saturating ADP’. State 3 respiration, therefore, may be less than level flow, if limited by non-saturating ADP concentrations (State 3 respiration < P) or by the capacity of the phosphorylation system (State 3 respiration < E).
» For comparison and references, see Static head.

Why not 'State 3u'?

Electron transfer-pathway versus electron transport chain

Biochemical coupling efficiency: from 0 to <1

MitoPedia concepts: Respiratory state, Find, Ergodynamics 

MitoPedia topics: EAGLE