It is easy to forget how crowded cells are. The criss-crossing cytoskeletal network is punctuated by organelles and macromolecules so that the only molecules that can freely diffuse between the structures are small molecules. But the organisation of complex cellular environments is determined by cellular function. While all types of muscle produce movement by contraction,the differing speeds and strength of contractions, as well as their voluntary or involuntary control, determines their underlying structure. Research has found, however, that the diffusion of metabolites across muscle fibres occurs in much the same way, whether the muscle comes from lobster, fish or mammals(p. 3377).
Stephen Kinsey and Timothy Moerland follow the movement of metabolites in intact muscle fibres using pulsed-field gradient nuclear magnetic resonance. Using this popular technique, Kinsey and Moerland calculate the displacement of molecules in the fibre by magnetically labelling their position and tracking them over time. `Time is...
