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Related Concept Videos

Diversity in Cell Signaling Responses01:22

Diversity in Cell Signaling Responses

The physiological function of a cell and cellular communication are outcomes of a range of extrinsic signals, intracellular signaling pathways, and cellular responses. No two cell types express the same repertoire of signaling components. Receptors are highly selective for their cognate ligands, but once activated, they can alter multiple cellular processes such as DNA transcription, protein synthesis, and metabolic activity. 
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Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Cell Signaling Feedback Loops01:07

Cell Signaling Feedback Loops

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An important concept in studying metabolism and energy is that of chemical equilibrium. Most chemical reactions are reversible. They can proceed in both directions, releasing energy into their environment in one direction, and absorbing it from the environment in the other direction. The same is true for the chemical reactions involved in cell metabolism, such as the breaking down and building up of proteins into and from individual amino acids, respectively. Reactants within a closed system...
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Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
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Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
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Related Experiment Video

Updated: Jun 6, 2026

Measuring Microbial Mutation Rates with the Fluctuation Assay
07:44

Measuring Microbial Mutation Rates with the Fluctuation Assay

Published on: November 28, 2019

Fluctuation and response in biology.

Ben Lehner1, Kunihiko Kaneko

  • 1EMBL-CRG Systems Biology Unit, ICREA, CRG, UPF, Barcelona, Spain. ben.lehner@crg.es

Cellular and Molecular Life Sciences : CMLS
|December 1, 2010
PubMed
Summary

Albert Einstein's fluctuation-response relationship from physics may explain biological systems. This principle links random motion to responsiveness, suggesting biological evolution is influenced by noise and perturbations.

Area of Science:

  • Physics
  • Evolutionary Biology
  • Systems Biology

Background:

  • Albert Einstein's 1905 work established a fluctuation-response relationship in physics, linking random motion (stochastic behavior) to resistance to macroscopic motion (non-stochastic behavior).
  • This fundamental principle has primarily been applied within physics, exploring the connection between system fluctuations and their responsiveness to external forces.

Purpose of the Study:

  • To propose and explore the relevance of Einstein's fluctuation-response relationship in the context of evolved biological systems.
  • To present a biological 'fluctuation-response relationship' that accounts for perturbations in biological systems.

Main Methods:

  • Theoretical argument extending the fluctuation-response concept from physics to biology.
  • Analysis of existing biological observations and in silico evolution experiments.

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  • Examination of the relationship between gene expression noise and evolvability.

    • Main Results:

    • Biological systems exhibit a fluctuation-response relationship, similar to physical systems.
    • This relationship is consistent with biological systems being canalized against stochastic, environmental, and genetic perturbations.
    • 'Noisy' gene expression correlates with increased responsiveness and evolvability.

    Conclusions:

    • Einstein's fluctuation-response insight is applicable to understanding evolved biological systems.
    • Biological systems demonstrate a capacity to respond to and evolve from perturbations, influenced by inherent noise.
    • Macroscopic theories, focusing on general system behavior over molecular details, are crucial for biological understanding.