Tuesday, December 1, 2009

importance of water in cell-2nd unit-cellbiology-btechbiotechnology

the water inside the cell affects its function:

1. The water mostly acts as an uncomplicated environment for the cellular processes, which are determined by the structure of the macromolecules only. Although this view seems the one most promoted in current textbooks by default, it is rapidly losing favour due to its inability to explain natural processes.
2. The water forms polarised multi-layers over extended protein surfaces, as proposed for many years by Gilbert Ling [1]. There is much experimental support for the foundations of this theory but little experimental support for the required structural changes in the proteins or the involvement of extended protein surfaces, as proposed.
3. The water is involved in intracellular changes between ‘sol’ and ‘gel’ states as more recently promoted by Gerald Pollack [2]. This is an interesting and useful idea but without a clear molecular mechanism.
4. The water actively changes the density of its hydrogen bonded structuring to enable diverse intracellular processes, in a manner compatible with the basic ideas of both Gilbert Ling and Gerald Pollack.
The differences in intracellular and extracellular environments of cells is primarily due to the extensive surface area and high intracellular concentration of solutes that promote the low-density clustering of water and restricted diffusion inside cells. The extensive surface of cellular membranes (e.g., each liver cell contain ~100 000 mm2 membrane surface area) favours the formation of low-density water inside cells, as the membrane lipids contain hydrophilic head groups that encourage this organization of the associated interfacial water. Other surfaces attract the water, so stretching the hydrogen-bonded water contained by the confined spaces within the cells.
importance of physical, as well as biochemical, processes of the cell, which focus attention on such straightforward elementary questions as position and relationship in space of cell components. In this communication these questions are examined in terms of a new model of water structure. A radically new feature of this model is that water clusters have long-term rather than flickering existence and are as large as the macromolecular components of the cell. These properties allow the clusters and other components to pack together spatially so giving rise to integrated, large-scale, subcellular structures.
role of water
1. Acts as an environment for cellular processes (metabolism etc.)
2.Essential for ensuring that various structures (proteins especially) are properly shaped. This is due to its polar nature.
3. Acts as a mode of transport by providing a solution that maintains a concentration gradient between the cell and its extracellular space. (Essential for transport into and out of cells)
* Intracellular water favours K+ ions over Na+ ions.
* Freely rotating proteins create zones of higher density water, which tend towards a lower density clustering if the rotation is prevented.
* Static charge-dense intracellular macromolecular structures prefer K+ ion pairs to freely soluble K+ ions.
* Ion paired K+-carboxylate groupings prefer local clathrate water structuring.
* Clathrate water prefers local low density water structuring.
* Low density water structuring can reinforce the low-density character of neighbouring site water structuring.
* Na+ and Ca2+ ions can destroy the low density structuring in a cooperative manner.

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