Cell ergometry

{{MitoPedia |description=Biochemical cell ergometry aims at measurement of J_O2max (compare V_O2max or V_O2peak in exercise ergometry of humans and animals) of cell respiration linked to phosphorylation of ADP to ATP. The corresponding OXPHOS capacity is based on saturating concentrations of ADP, [ADP], and inorganic phosphate [Pi] available to the mitochondria. This is metabolically opposite to uncoupling of respiration, which yields ET capacity. The OXPHOS state can be established experimentally by selective permeabilization of cell membranes with maintenance of intact mitochondria, titrations of ADP and P_i to evaluate kinetically saturating conditions, and establishing fuel substrate combinations which reconstitute physiological TCA cycle function. Uncoupler titrations are applied to determine the apparent ET-pathway excess over OXPHOS capacity ([[E-P control efficiency |E-P control efficiency) and to calculate the P-L control efficiency j_P-L and E-L coupling efficiency j_E-L. These normalized flux ratios are the basis to calculate the ergometric or ergodynamic efficiency, ε = j · f, where f is the normalized force ratio.

» MiPNet article |info=Gnaiger 2020 BEC MitoPathways, Oxygen flux }}

Cell ergometry and OXPHOS

Gnaiger E (2015) Cell ergometry and OXPHOS. Mitochondr Physiol Network 2015-01-18.

Oroboros (2015) MiPNet

Abstract: Spiroergometry on the organismic level is compared to cell ergometry as OXPHOS analysis on the cellular level.

• O2k-Network Lab: AT Innsbruck Gnaiger E

Spiroergometry

V_O2max or V_O2peak in cycle or treadmill spiroergometry is expressed in units of [mL O₂·min^-1·kg^-1] body mass. 1 mL oxygen at STPD is equivalent to 22.392 mmol O₂. Therefore, multiply by 1000/(22.392·60)=0.744 to convert V_O2max to J_O2max expressed in SI units [nmol·s^-1·g^-1]:

1 mL O2·min-1·kg-1 = 0.744 µmol·s-1·kg-1

V_O2max (J_O2max) typically declines from 70 to 25 mL O₂·min^-1·kg^-1 (50 to 20 µmol·s^-1·kg^-1) in the range of healthy trained to obese untrained humans.

Keywords

• Expand Bioblast links to Cell ergometry

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  The Blue Book 2020
  

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  OXPHOS-, ROUTINE-, ET-, and LEAK states; respiratory capacities (P, R, E, L) corrected for residual oxygen consumption Rox.

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  4-compartmental OXPHOS model. (1) ET capacity E of the noncoupled electron transfer system ETS. OXPHOS capacity P is partitioned into (2) the dissipative LEAK component L, and (3) ADP-stimulated P-L net OXPHOS capacity. (4) If P-L is kinetically limited by a low capacity of the phosphorylation system to utilize the protonmotive force pmF, then the apparent E-P excess capacity is available to drive coupled processes other than phosphorylation P» (ADP to ATP) without competing with P».

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  (P-L)/P is the OXPHOS P-L control efficiency. The biochemical coupling efficiency is independent of kinetic control by the phosphorylation system when expressed as the E-L coupling efficiency, (E-L)/E. (E-P)/E is the kinetic E-P control efficiency.

Bioblast links: Coupling control - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>

1. Mitochondrial and cellular respiratory rates in coupling-control states

» Baseline state

Respiratory rate	Defining relations	Icon
OXPHOS capacity	P = P´-Rox		mt-preparations
ROUTINE respiration	R = R´-Rox		living cells
ET capacity	E = E´-Rox		» Level flow
			» Noncoupled respiration - Uncoupler
LEAK respiration	L = L´-Rox		» Static head
			» LEAK state with ATP
			» LEAK state with oligomycin
			» LEAK state without adenylates
Residual oxygen consumption Rox	L = L´-Rox

• Chance and Williams nomenclature: respiratory states

» State 1 —» State 2 —» State 3 —» State 4 —» State 5

2. Flux control ratios related to coupling in mt-preparations and living cells

» Flux control ratio

» Coupling-control ratio

» Coupling-control protocol

FCR	Definition	Icon
L/P coupling-control ratio	L/P		» Respiratory acceptor control ratio, RCR = P/L
L/R coupling-control ratio	L/R
L/E coupling-control ratio	L/E		» Uncoupling-control ratio, UCR = E/L (ambiguous)
P/E control ratio	P/E
R/E control ratio	R/E		» Uncoupling-control ratio, UCR = E/L
net P/E control ratio	(P-L)/E
net R/E control ratio	(R-L)/E

3. Net, excess, and reserve capacities of respiration

Respiratory net rate	Definition	Icon
P-L net OXPHOS capacity	P-L
R-L net ROUTINE capacity	R-L
E-L net ET capacity	E-L
E-P excess capacity	E-P
E-R reserve capacity	E-R

4. Flux control efficiencies related to coupling-control ratios

» Flux control efficiency j_Z-Y

» Background state

» Reference state

» Metabolic control variable

Coupling-control efficiency		Definition		Icon	Canonical term
P-L control efficiency	jP-L	= (P-L)/P	= 1-L/P		P-L OXPHOS-flux control efficiency
R-L control efficiency	jR-L	= (R-L)/R	= 1-L/R		R-L ROUTINE-flux control efficiency
E-L coupling efficiency	jE-L	= (E-L)/E	= 1-L/E		E-L ET-coupling efficiency » Biochemical coupling efficiency
E-P control efficiency	jE-P	= (E-P)/E	= 1-P/E		E-P ET-excess flux control efficiency
E-R control efficiency	jE-R	= (E-R)/E	= 1-R/E		E-R ET-reserve flux control efficiency

5. General

» Basal respiration

» Cell ergometry

» Dyscoupled respiration

» Dyscoupling

» Electron leak

» Electron-transfer-pathway state

» Hyphenation

» Oxidative phosphorylation

» Oxygen flow

» Oxygen flux

» Permeabilized cells

» Phosphorylation system

» Proton leak

» Proton slip

» Respiratory state

» Uncoupling

MitoPedia concepts: MiP concept, Ergodynamics 

MitoPedia methods: Respirometry 

Labels:

Regulation: Coupling efficiency;uncoupling  Coupling state: LEAK, OXPHOS, ET  Pathway: N, S, NS, ROX  HRR: Theory