As Biology - Biological Molecules - Water

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Four functions of water:

  • Water is a reactant in loads of important chemical reactions, like photosynthesis, and hydrolysis reactions.
  • Water is a solvent, which means some substances dissolve in it. Most biological reactions take place in solution, so water's pretty essential.
  • Water transports substances. The fact that it's a liquid and a solvent means it can easily transport all sorts of materials, like glucose and oxygen, around plants and animals.
  • Water helps with temperature control. It carries away heat energy when it evaporates from a surface. This cools the surface and helps to lower the temperature.

Simple structure:

  • A molecule of water is one atom of oxygen joined to two molecules of hydrogen by shared electrons.
  • Because the shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of each hydrogen atom is left with a slight positive charge.
  • The unshared negative electrons on the oxygen atom give it a slight negative charge.
  • This makes water a polar molecule - it has a negative charge on one side and a positive charge on the other.


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