Hot Mitochondria and the Second Law of Thermodynamics

Hot Mitochondria and the Second Law of Thermodynamics | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hot Mitochondria and the Second Law of Thermodynamics Alexei Tkachenko, Belem Yoval-Sánchez, Alexander Galkin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8744427/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Mitochondria are central hubs of cellular bioenergetics, converting chemical free energy into ATP while inevitably releasing heat during respiration. Fluorescence-based thermometry has been interpreted to show intracellular “hot spots” more than 10 °C above the bulk physiological temperature, implying that mitochondria might operate far outside conventional thermal bounds. Such claims, however, appear inconsistent with basic biophysics: the small size of mitochondria, their aqueous and highly conductive environment, and their limited power output all argue against large steady-state temperature gradients. This discrepancy has prompted renewed scrutiny of both the physical limits of intracellular heat transfer and the biological interpretation of nanoscale thermal measurements. A key open question is whether nonequilibrium biochemical processes, such as respiration-driven proton pumping, could act as nanoscale heat pumps that maintain higher local temperatures than allowed by passive diffusion alone. Here, we develop a model-independent thermodynamic analysis based solely on the Second Law of Thermodynamics to bound the maximal temperature difference that any biochemically driven mechanism can sustain across the inner mitochondrial membrane and show that even under idealized conditions the achievable temperature rise is restricted to a small fraction of a degree, effectively closing this loophole. Biological sciences/Biophysics Biological sciences/Cell biology Physical sciences/Physics Biological sciences/Physiology Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 15 Apr, 2026 Reviews received at journal 27 Mar, 2026 Reviews received at journal 06 Mar, 2026 Reviewers agreed at journal 03 Mar, 2026 Reviewers agreed at journal 18 Feb, 2026 Reviewers invited by journal 17 Feb, 2026 Editor assigned by journal 04 Feb, 2026 Submission checks completed at journal 03 Feb, 2026 First submitted to journal 30 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8744427","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":593383711,"identity":"85232db2-2461-4789-9104-4669b8abce39","order_by":0,"name":"Alexei Tkachenko","email":"","orcid":"","institution":"Brookhaven National Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Alexei","middleName":"","lastName":"Tkachenko","suffix":""},{"id":593383714,"identity":"586891b1-597a-4592-8cd3-4a2fd01546e3","order_by":1,"name":"Belem Yoval-Sánchez","email":"","orcid":"","institution":"Weill Cornell Medicine","correspondingAuthor":false,"prefix":"","firstName":"Belem","middleName":"","lastName":"Yoval-Sánchez","suffix":""},{"id":593383717,"identity":"a20fc563-23e5-4199-880d-b472844fef8f","order_by":2,"name":"Alexander Galkin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIiWNgGAWjYDACdgbGB4l//ssBmQZQEeYGBgY2PFqYGZgNPjYwGyO0MDMS1MImObOBObGBaC38zewXpHl3sKWvbW/ewPCj4l4eP0jLh7LDOLVIHOYpMOY9w5O77cyxAsaeM8XFks2MDYwzzuHWwnCYJyGZh00id9uNHANmxraExA2HGRuYedtwa5EHajnMw2aQbnb/DUTLfpCWv3i0GBxmP9g4sy0hwewGD9QWoF+ADNxaDA/zMDN8OHPAcNuZtIKDPWcSEmcAbTnYcy4dpxa54+3PfyRUHJA3O35444MfFQmJ/e3NBx/8KLPG7X0GHgM48wAGAztgf4BffhSMglEwCkYBAKrTWyqqq5ylAAAAAElFTkSuQmCC","orcid":"","institution":"Weill Cornell Medicine","correspondingAuthor":true,"prefix":"","firstName":"Alexander","middleName":"","lastName":"Galkin","suffix":""}],"badges":[],"createdAt":"2026-01-30 19:23:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8744427/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8744427/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103050594,"identity":"ab55374f-8406-4237-b6f7-d7470f2db9dd","added_by":"auto","created_at":"2026-02-20 07:50:43","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":268386,"visible":true,"origin":"","legend":"","description":"","filename":"Mitochondria.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8744427/v1_covered_1e94e380-060e-40ef-9bc4-414f974d8626.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hot Mitochondria and the Second Law of Thermodynamics","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-biological-physics-and-mechanics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [npj Biological Physics and Mechanics](https://www.nature.com/npjbiolphysmech)","snPcode":"44341","submissionUrl":"https://submission.springernature.com/new-submission/44341/3","title":"npj Biological Physics and Mechanics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"NPJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8744427/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8744427/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Mitochondria are central hubs of cellular bioenergetics, converting chemical free energy into ATP while inevitably releasing heat during respiration. 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