1.7 Water

• water is a dipolar molecule as it has 2 charges, hydrogen atoms being slightly positive and oxygen atoms are slightly negative
• Properties of water-

  • metabolite
  • large latent heat of vaporisation
  • high specific heat capacity
  • strong cohesion
  • solvent
• non polar molecules like lipids don’t dissolve in water
• high specific heat capacity

  • it takes a lot to heat water 1 degree due to large number of hydrogen bonds
  • therefore lots of energy is required to break these bonds so small temperature rise
  • useful for organisms as it reduces fluctuations in internal temperatures
  • prevents denaturing of proteins
• large latent heat of vaporisation

  • a lot of energy is required to convert water into a gas
  • a lot of energy is required to break the hydrogen bonds
  • useful for organisms because it enables them to regulate temperatures
  • when water evaporates the thermal energy is carried away so it cools the body
• water is a metabolite in these reactions

  • condensation
  • hydrolysis
  • photosynthesis
• cohesive

  • hydrogen bonds make water molecules stick together
  • important in plants- transpiration stream and molecules dissolve in water through the xylem via capillary action
  • important in animals- water sticks together so transport of water in the blood and provides surface extension to water so insects can live on the surface
• solvent

  • being dipolar, water dissolves charged, polar molecules
  • hydrates ionic molecules, form solvation shells- water surrounds charged particles pulling them into solution