The Importance Of Water

Water

Water is one of the most outstanding molecules known to man and also one of the most important to biological systems. Not only does water exist in nature in all three states of matter (solid, liquid, gas), it also covers 75 percent of the earth and composes approximately 78 percent of the human body.The distinctiveness of water comes from its molecular structure. Because it is a polar covalent molecule, it has a slight positive and slight negative charge on opposite ends.

Properties Of Water

Property Remarks Importance to the environment

Physical state Only substance occurring naturally in all three phases as solid, liquid, and gas on Earth's surface Transfer of heat between ocean and atmosphere by phase change

Dissolving ability Dissolves

The hydrophobic effect and hydrogen bonds are of chief importance and water is essential in these contributions to protein structure and stability. The hydrophobic effect is usually considered to be the main driving force for the folding of globular proteins. It results in the burial of the hydrophobic amino acid side-chains in the core of the protein. Water tends to form ordered cages around non-polar groups (hydrophobic hydration) which leads to a decline in entropy of the system. These water molecules gain entropy when they are released after hydrophobic surfaces are put in touch with each other. This contributes in a very positive way to the free energy of stabilisation of the protein. Water is therefore essential in protein folding because of its role in defining hydrophobic

Phosphate-phosphate electrostatic repulsion is diminished in water by the high dielectric constant of water. As in proteins, water is a fundamental part of nucleic acid structures. A shell of hydration, impermeable to cations, is located around DNA double helices . It consists of about 18-19 water molecules per nucleotide in B-DNA and of about 13-14 in A-DNA. Like for proteins this shell of hydration has a major role in recognition processes .

5)Role of water in molecular recognition involving bio-molecules

Binding processes are everywhere in biological systems ranging from the binding of minute molecules like drugs to binding of proteins to DNA. Water is a highly versatile element at the boundary of biomolecular complexes. It can operate both as a hydrogen bond donor and acceptor, commanding few steric constraints on bond formation and can take part in several hydrogen bonds.

Water in protein-ligand interactions can for example act as an extension of protein structure allowing various ligands to be accommodated in a given binding site or increasing affinity for particular