Cytoplasmic streaming: Helical shear flows in giant algal cells and their implications for molecular transport

Condensed Matter lunchtime seminar

Cytoplasmic streaming: Helical shear flows in giant algal cells and their implications for molecular transport

  • Event time: 1:00pm
  • Event date: 21st January 2008
  • Speaker: Jan Willem van de Meent (DAMTP University of Cambridge)
  • Location: Room 2511,

Event details

Found in many large eukaryotic cells, particularly in plants, cytoplasmic streaming is the circulation of their contents driven by fluid entrainmentfrom organelles carried by molecular motors at the cell periphery. In the more than 2 centuries since its discovery, streaming has frequently been conjectured to aid in transport and mixing of molecular species in the cytoplasm, and, by implication, in cellular homeostasis, yet no mechanism quantifying this enhancement has been demonstrated.

We solve the flow and its associated advection-diffusion equations for the archetypal ''rotational streaming'' found in Characean algae, where the cytoplasm streams up and down along helical bands on the cylindrical surface of giant ''internodal'' cells with lengths as large as 10 cm. We find that the spiralling flow induces a secondary circulation, reminiscent of Dean vortices found at higher Reynolds numbers, which leads to the formation of a high-flux boundary layer allowing faster uptake and response to changes in external concentration. This effect constitutes a novel example of how high Peclet number flows can facilitate diffusive transport and mixing at the micro-scale.

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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