How Water Contributes To The Structure And Behavior Of Biological Molecules

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Introduction

Water,H2O, is one of the most important chemical compounds on earth, and is commonly referred to as the basis of life on earth, because it is used in all type of chemical and biological processes, e.g. solvent, protein folding, stability of nucleic acids etc. Water is found in 3 states (solid, liquid, and gas), and is the most abundant naturally occurring substance on earth, covering 75% of the earth surface.

Structure

Water consists of 2 hydrogen atoms and 1 oxygen atoms, (held together by covalent bonds between the O-H atoms) and 2 lone pair of electrons on the oxygen atom, resulting in the formation of a bent shape with a bond angle of 104.5⁰. These 2 lone pair of electrons means that water has a tetrahedral
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The oxygen atom in water molecules contain 2 lone pair of electrons which have a negative charge and therefore repel each other, thus they move further apart. This consequence of this movement of lone pair is the O-H bonds move closer together and due to water’s bent shape ‘the distortion of charge is asymmetric’ (Quotes from Biochemistry, 2011 page 8). However, this means the hydrogen atoms now have a slightly positive charge (δ+), meaning that water is a polar molecule (Figure 2). This property is highly important in allowing water to carry out its many functions.(Biochemistry, 2011)

Non-polar molecules cannot form hydrogen or ionic bonds. When in solution water surrounds non-polar molecules which become well ordered and therefore have lower entropy, unlike free water molecules in solution. However, when two non-polar molecules surrounded by water molecules come together, the water ‘cages’ (Quotes from Biochemistry, 2011 page 9) join together and some water molecules are released, increasing the entropy of the system (Biochemistry, 2011). The ability for non-polar molecules to join together in water is more favorable than with less polar solvents. This is known as the hydrophobic effect, and is one of the most important properties of water, because it allows water to be used as a universal solvent, used in protein folding etc (Wikipedia- hydrophobic effect). The hydrophobic effect is a importance part of the

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