Biological complexity: molecular transport in cells (Introduction)

by David Turell , Thursday, November 05, 2015, 15:52 (3306 days ago) @ David Turell

Kinesin walks across microtubules carrying the molecule:-http://phys.org/news/2015-11-ministry-silly-cells.html-"Intracellular transport takes place along the fibres of the cytoskeleton, a structure developed by eukaryotic cells (possessing a cell nucleus). The fibres forming the network - microtubules - are made of polymers of the protein tubulin twisted spirally into long tubes. Since each 'brick' of the polymer, i.e., each monomer, consists of a pair of alpha-tubulin and beta-tubulin. Along the microtubule, the alpha and beta domains are arranged alternately, like the black-and-white squares along the length of a chessboard if it were rolled up into a tube.-"The microtubules are the roads along which the intracellular tractors, the kinesin molecules, move. One part of kinesin is equipped with fragments that bind to molecules in order to transport them, while the driving part consists of a flexible connector, the so-called linker, fastening together the two 'legs', i.e. the movable domains that step along the 'chess fields' of the microtubules. In addition, the legs are so large that kinesin can only step on every second monomer (that is, fields of the same colour).-"'Kinesin walks along the microtubules. But how? In order to understand the problem, one needs only to realize that kinesin does not wander along the microtubules like a man does along the pavement. Its movements are more reminiscent of what a mountain climber does when scaling a vertical wall without any safeguards: one mistake, and he falls off," says Prof. Robert Holyst (IPC PAS). "How does kinesin know it can free one leg without risking detachment from the microtubules? It isn't an animal equipped with eyes and a brain, it's just a simple molecule. Where does it get the energy to take the step?'"-Comment: Play the video to really understand what this process looks like. Of course chance invention cannot create this.