Document Detail


Diffusion theory, the cell and the synapse.
MedLine Citation:
PMID:  9544405     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The possibility exists that the cell internum is far more highly organised right down to the molecular level than was hitherto appreciated, to the point where ideas of a relatively solid-state chemistry model have been entertained (Coulson, R.A., 1993. The flow theory of enzyme kinetics--a role of solid geometry in the control reaction velocity in live animals. Int. J. Biochem. 25, 1445-1474). This contrasts sharply with the traditional dogma that diffusion is the mechanism by which molecules interact within an aqueous solution of the cell internum, although it should have been clear from an early stage that diffusion could not play other than a very restricted role in metabolic regulation. When physicists began to question certain aspects of the fundamental Law of Heat Conductance formulated over 170 years ago by Fourier, Diffusion Theory was also implicated (Maddox, J., 1989. Heat conductance is a can of worms. Nature 338, 373), and application of Fick's Laws of Diffusion to living systems criticised (Agutter P.S., Malone, P.C., Wheatley, D.N., 1995. Intracellular transport mechanisms: a critique of diffusion theory. J. Theoret. Biol. 176, 261-272). While we have argued (Wheatley, D.N., Malone, P.C., 1993. Heat conductance, diffusion theory and intracellular metabolic regulation. Biol. Cell 79, 1-5) that diffusion cannot be prevented from occurring, we found that, irrespective of whether it was a valid theory, diffusion was of little relevance in most actively metabolising cell systems. However, diffusion is still perceived as essential for interacting molecules to demonstrate their specificities. Any new model of the internal state of the living cell has to resolve this dilemma. The question also relates to molecular movement and ligand-receptor interactions outside the cell. In looking at this situation, attention was paid to one site in the body in which diffusion has long been assumed to be essential, namely in the passage of the chemical transmitter between one neurone and the next across the synaptic cleft. A detailed examination of this assumption has helped to identify one possible place in which the importance of diffusion over a distance of no more than 20-30 nm occurs, although objections to diffusion being involved have been raised. The outcome, however, only re-enforces the conviction that diffusion has little role in metabolic activity and is normally 'assisted' in almost all aspects of cell physiology.
Authors:
D N Wheatley
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Bio Systems     Volume:  45     ISSN:  0303-2647     ISO Abbreviation:  BioSystems     Publication Date:  1998 Feb 
Date Detail:
Created Date:  1998-06-01     Completed Date:  1998-06-01     Revised Date:  2009-09-29    
Medline Journal Info:
Nlm Unique ID:  0430773     Medline TA:  Biosystems     Country:  IRELAND    
Other Details:
Languages:  eng     Pagination:  151-63     Citation Subset:  IM    
Affiliation:
Cell Pathology Unit, University Medical School, Foresterhill, Aberdeen, UK. wheatley@abdn.ac.uk
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MeSH Terms
Descriptor/Qualifier:
Action Potentials / physiology
Animals
Cell Physiological Phenomena*
Diffusion
Models, Neurological*
Movement
Synapses / physiology*
Synaptic Transmission / physiology
Grant Support
ID/Acronym/Agency:
//Wellcome Trust

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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