How hot are single cells?

Balaban, Robert S.

doi:10.1085/jgp.202012629

Cited by 15 publications

(9 citation statements)

References 39 publications

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“…30,31 The key parameters in this equation are the mass of gamma subunit (𝑀 𝛾 ) which is 30,337 dalton, 60 and the rate of proton translocation through the intact (complete) ATP synthase (𝑛̇) which is roughly 1200 protons/s (or ~ 1 proton/0.00083 s). 36 Eqn (6) suggests that 𝛼 ≪ 1, that is, 𝛼 is negligible in comparison with unity (but 𝛼 is not zero). The smallness of 𝛼 implies that the axle (spring) is torsionally soft.…”

Section: Thermal Conductance Of Atp Synthase As a Maxwell's Demonmentioning

confidence: 99%

“…5 2 Hence, in a nutshell, the first step undertaken by Nasr et al, and which is a qualitative examination of the consistency of the available evidence with Chrétien's claim of a hotter mitochondrion, appears to reinforce this claim (see also discussions in Refs. [3][4][5][6][7][8]. The more challenging task, that of providing a quantitative estimation of the temperature gradient from an alternative route to confirm, refute, or modify the 10 o C temperature difference, remains an open question.…”

Section: Introductionmentioning

confidence: 99%

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The hot mitochondrion paradox: reconciling theory and experiment

Fahimi

Matta

2022

Trends in Chemistry

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Experiments by Chrétien and coworkers suggest that mitochondria are 10°C hotter than their surroundings. Steady-state theoretical estimates place this difference at a maximum of 10 −5 °C. This millionfold disagreement may be called the 'hot mitochondrion paradox'. It is suggested that every proton translocated via ATP synthase sparks a picosecond temperature-difference spike of the order of magnitude measured by Chrétien et al. Time averaging of these spikes recovers the theoretical value. Further, a temporal and spatial superposition of the fluorescence intensity of a very large number of molecular thermometer molecules in the sample can give the appearance of a steady signal. The inner mitochondrial membrane appears to be flanked by temperature differences fluctuating in time and along the membrane's surface, with 'hot' and 'cold' spots as ultrashort temperature spikes. An apparent millionfold disagreement of theory and experiment HighlightsExperiments suggest a 10°C temperature difference between the mitochondrion and its surroundings in a millionfold disagreement with steadystate theoretical estimates.Both experiment and theory appear to be solidly founded, so we have a paradox.ATP synthase is modelled as a modified Feynman ratchet engine coupling two separate heat baths.The paradox is resolved by understanding that the appearance of the steady measurement of a temperature difference is the result of continually recording sharp, picosecond spikes of temperature difference the time averaging of which leads to the theoretical value.

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Section: Thermal Conductance Of Atp Synthase As a Maxwell's Demonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The hot mitochondrion paradox: reconciling theory and experiment

Fahimi

Matta

2022

Trends in Chemistry

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“…83 Several issues have been raised in opposition of these findings, such as: (i) methodological concerns specific to research utilizing fluorescent probes for determination of cellular temperatures that includes possibly confounding influence(s) of the surrounding environment (ie pH, reactive oxygen species, membrane potential, viscosity and ionic strength); (ii) thermodynamic modelling of the cell describing the so-called "10 −5 gap" theory that renders intracellular temperature gradients as all but impossible and (iii) biological improbabilities of such high in vivo temperatures that would challenge human biological function as we understand it. [96][97][98] Thus, considerations for appropriate temperature corrections range from a minimum that reflects the cellular temperature specific to the tissue being analysed when taking into account the metabolic state also being measures (ie basal vs maximal metabolic states) to a maximum of 10°C above that minimum value. As noted previously, temperature corrections used to reflect the temperature of the exercising muscle (eg 38°C) are still lower than in vivo methodologies identify.…”

Section: Aim 3a: Temperature Correcting Standardized Hrr Measures Wmentioning

confidence: 99%

Contextualizing the biological relevance of standardized high‐resolution respirometry to assess mitochondrial function in permeabilized human skeletal muscle

Jacobs

Lundby

2021

Acta Physiologica

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Aim This study sought to provide a statistically robust reference for measures of mitochondrial function from standardized high‐resolution respirometry with permeabilized human skeletal muscle (ex vivo), compare analogous values obtained via indirect calorimetry, arterial‐venous O2 differences and 31P magnetic resonance spectroscopy (in vivo) and attempt to resolve differences across complementary methodologies as necessary. Methods Data derived from 831 study participants across research published throughout March 2009 to November 2019 were amassed to examine the biological relevance of ex vivo assessments under standard conditions, ie physiological temperatures of 37°C and respiratory chamber oxygen concentrations of ~250 to 500 μmol/L. Results Standard ex vivo‐derived measures are lower (Z ≥ 3.01, P ≤ .0258) en masse than corresponding in vivo‐derived values. Correcting respiratory values to account for mitochondrial temperatures 10°C higher than skeletal muscle temperatures at maximal exercise (~50°C): (i) transforms data to resemble (Z ≤ 0.8, P > .9999) analogous yet context‐specific in vivo measures, eg data collected during maximal 1‐leg knee extension exercise; and (ii) supports the position that maximal skeletal muscle respiratory rates exceed (Z ≥ 13.2, P < .0001) those achieved during maximal whole‐body exercise, e.g. maximal cycling efforts. Conclusion This study outlines and demonstrates necessary considerations when actualizing the biological relevance of human skeletal muscle respiratory control, metabolic flexibility and bioenergetics from standard ex vivo‐derived assessments using permeabilized human muscle. These findings detail how cross‐procedural comparisons of human skeletal muscle mitochondrial function may be collectively scrutinized in their relationship to human health and lifespan.

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“…Many articles consider whether temperature gradients can be maintained within single cells 34,35 . The current consensus suggests that significant intracellular gradients are unlikely because heat diffuses too quickly within cells and across membranes 36,37 .…”

Section: Heat Flow and Spatial Scalementioning

confidence: 99%

Metabolic Heat in Microbial Conflict and Cooperation

Frank¹

2020

Preprint

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Many microbes live in habitats below their optimum temperature. Retention of metabolic heat by aggregation or insulation would boost growth. Generation of excess metabolic heat may also provide benefit. A cell that makes excess metabolic heat pays the cost of production, whereas the benefit may be shared by neighbors within a zone of local heat capture. Metabolic heat as a shareable public good raises interesting questions about conflict and cooperation of heat production and capture. Metabolic heat may also be deployed as a weapon. Species with greater thermotolerance gain by raising local temperature to outcompete less thermotolerant taxa. Metabolic heat may provide defense against bacteriophage attack, by analogy with fever in vertebrates. This article outlines the theory of metabolic heat in microbial conflict and cooperation, presenting several predictions for future study.

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How hot are single cells?

Abstract: Large changes in energy metabolism are associated with minimal alterations in surface temperature of isolated mammalian cells.

Cited by 15 publications

References 39 publications

The hot mitochondrion paradox: reconciling theory and experiment

The hot mitochondrion paradox: reconciling theory and experiment

Contextualizing the biological relevance of standardized high‐resolution respirometry to assess mitochondrial function in permeabilized human skeletal muscle

Metabolic Heat in Microbial Conflict and Cooperation

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