water

• functions of water:

  • metabolite: important in many metabolic reactions- condensation & hydrolysis
  • solvent: substances can dissolve in it. the metabolic reaction is the solution (e.g. cytoplasm) so water involved
  • help's temperature control: high latent heat of vapourisation & high specific heat capacity
  • cohesive (stick together): helps water transport in plants and transport in other organisms
• water structure:

  • one O atom and two H atoms, share electrons
  • H atoms slightly positive, O atoms slightly negative charge, has positive and negative charge so is dipolar
  • slight delta negative charge on O atoms attract slightly delta positive charge H atoms on other H2O molecules: forms H bonds between O and H atoms
• water in metabolism:

  • involve condensation & hydrolysis
  • chemical reaction in aqueous medium
  • H2O major in photosynthesis
• water has high latent heat of vaporisation:

  • takes lots of energy to break H bonds between H2 molecules
  • lots of heat used to vaporise: high latent heat of vapourisation
  • useful for organisms, because water loss through evaporation to cool down without losing to much H2O
• water acts as a buffer:

  • resists changes in temp
  • H bonds between H2O molecules can absorb a lot of energy
  • high specific heat capacity- takes lots energy to heat up
  • useful for organisms: water doesn't have rapid changes in temp; good habitat as stable temp, help maintain constant internal body temp
• water is good solvent:

  • readily dissolve into:
  • gases : O & CO2
  • wastes: NH3 and urea
  • inorganic ions and small hydrophillic molecules e.g. AA, monosaccharides and ATP
  • enzymes, reaction take place in solution
• strong cohesion between H2O molecules:

  • H2O very cohesive: polar
  • strong cohesion= H2O flow easily, good for transport substances. e.g. H2O travels in columns of xylem
  • strong cohesion= high surface tension when in contact with air