Is a cell more like a solid or a liquid?

Neither alone; cells are viscoelastic, behaving elastically over short times and flowing over longer ones, because their cytoskeletal networks combine elastic and viscous responses.

Where does the force inside cells come from?

Largely from molecular motors that convert the chemical energy of ATP into mechanical steps along cytoskeletal filaments, and from the assembly and contraction of those filament networks.

Biomechanics

How biological matter generates, transmits, and responds to mechanical force—from the molecular motors that produce movement to the elastic networks that give cells and tissues their shape.

Definition

Biomechanics is the study of how biological systems produce, transmit, and respond to mechanical forces and deformations, from single molecules to tissues.

Scope

This area covers the mechanics of living matter at the molecular, cellular, and tissue scales: the elastic and viscoelastic properties of cells and tissues, the mechanics of the cytoskeleton, force generation by molecular motors, and the conversion of mechanical signals into biochemical responses. It treats biological structures as mechanical materials and machines, while leaving whole-organism locomotion and clinical orthopaedics to other fields.

Sub-topics

Core questions

What mechanical properties characterise cells and tissues, and how are they measured?
How does the cytoskeleton give cells their stiffness and shape?
How do molecular motors convert chemical energy into directed force and motion?
How do cells sense mechanical force and convert it into biochemical signals?

Key theories

Motors as mechanochemical cycles: Molecular motors couple a cycle of nucleotide binding and hydrolysis to conformational changes that produce discrete force-generating steps along a track, as measured directly for single myosin molecules.
Cells as viscoelastic, prestressed materials: Cellular mechanics is governed by cytoskeletal polymer networks under tension whose elastic and viscous responses, rather than a simple solid or fluid, set how cells deform and recover.

Mechanisms

Force in cells originates largely from molecular motors that step along cytoskeletal filaments by coupling ATP hydrolysis to conformational change, and from the assembly and contraction of filament networks. These networks behave as viscoelastic, often prestressed materials, so cells and tissues respond to deformation with both elastic recoil and viscous flow. Mechanical signals are not only transmitted but sensed: force-sensitive molecules change conformation under load, converting mechanics into chemistry and feeding back on the structures that bear the load.

Clinical relevance

Mechanical properties and force sensing influence development, wound healing, cardiovascular function, and cancer progression, so the biomechanics here is educational background for mechanobiology and physiology rather than clinical recommendation.

History

Continuum biomechanics of tissues, advanced by Fung among others, was joined in the late twentieth century by single-molecule mechanics—exemplified by direct measurement of myosin steps—and by the recognition that cells actively sense force, uniting molecular and tissue scales into modern mechanobiology.

Key figures

Jonathon Howard
James Spudich
Donald Ingber
Y. C. Fung

Seminal works

finer1994
howard2001
boal2012

Frequently asked questions

Is a cell more like a solid or a liquid?: Neither alone; cells are viscoelastic, behaving elastically over short times and flowing over longer ones, because their cytoskeletal networks combine elastic and viscous responses.
Where does the force inside cells come from?: Largely from molecular motors that convert the chemical energy of ATP into mechanical steps along cytoskeletal filaments, and from the assembly and contraction of those filament networks.