water

• why is water biologically important

  • Between 70% to 95% of the mass of a cell is water.
  • It is the medium in which all metabolic reactions take place in cells.
  • As 71% of the Earth’s surface is covered in water it is a major habitat for organisms.
• structure of water

  .

  A) oxygen

  B) polar covalent bond

  C) hydrogen

  D) hydrogen

  
• structure of water

  • water is composed of atoms of hydrogen and oxygen. one atoms of oxygen combines with 2 atoms of hydrogen by covalent bonding
  • although water as a whole is electrically neutral. the sharing of the electron is uneven between the oxygen and hydrogen atoms
  • the oxygen atom attracts the electrons more strongly than the hydrogen atoms resulting in weak, negatively charged region on the oxygen atom and a weak positively charged region on the hydrogen atoms, this also results in asymmetrical shape
• structure of water

  the seperation of charge due to the electrons in the covalent bonds being unevenly shared is called dipole. when a molecule has one end that is negatively charged and one end that is positively charged it is also a polar molecule
• structure of hydrogen bonds


  • hydrogen bonds form between water molecules
  • as a result of the polarity of water, hydrogen bonds form between the positively and negatively charged regions of adjacent water molecules
  • hydrogen bonds are weak, when there are a few so they are constantly breaking and reforming. however when there are large numbers present they form a strong structure
• properties hydrogen bonds contribute to in water


  • excellent solvent
  • relatively high specific heat capacity
  • relatively high latent heat of vaporisation
  • water is less dense when a solid
  • what has high surface tension and cohesion