Water

• Structure of water

  H20:

  • O is slightly negatively charged
  • H is slightly positively charged
  • Molecule is dipolar
  • Creates hydrogen bonding
• Water as a metabolite

  Many metabolic reactions involve a condensation or hydrolysis reaction

  • hydrolysis reactions requires a molecule of water to break a bond
  • a condensation reaction releases a molecule of water as a new bond is formed
• Good solvent

  Many biological reactions are ionic, meaning they're made from oppositely charged atoms

  • because water is slightly polar, the charged sides of the water molecule will be attracted to oppositely charged atoms, making it useful as a solvent and able to dissolve ions
  • this means that living organisms can take up useful substances dissolved in water, and transport them around the body
• High latent. heat of vaporisation

  Water evaporates when hydrogen bonds holding water molecules together are broken.

  • Takes a lot of energy to break the hydrogen bonds between water molecules, so a lot of energy so used when water evaporates
  • this is useful for living organisms because they can use water loss through evaporation to cool down without loosing much water
• High specific heat capacity

  Hydrogen bonds give water a high specific heat capacity ( the energy required to raise the temp of 1 gram of a substance by 1 degree celcius)

  • when water is heated, alot of energy used to break hydrogen bonds
  • this means theres less energy to actually increase temp of water
  • useful for organisms because means water doesnt experience rapid temperature changes
  • good habitat as water temp is more stable then land
• Cohesive

  Cohesion is the attraction between molecules of the same type

  • H20 is very cohesive because theyre polar
  • strong cohesion helps water to flow, good at transporting substances
  • for example up the xylem
• High surface tension

  When in contact with air

  • helps sweat droplets form, which evaporate from the skin to cool down an organisms
  • allows some insects to talk on surface of a pond