Molecules, Transport and health

• Structure of the water molecule

  1. Water molecule contains one atom of oxygen chemically bonded to two atoms of hydrogen

  2. Oxygen atom has a small negative charge and hydrogen atoms have a small positive charge

  3. Water is a polar molecule with opposite charges attracting each other

  4. Hydrogen bonds are weak but have a large effect on water properties
• Water is one of the most important molecules in biology
• Properties of water


  1. Water has a very high specific heat capacity

  2. Heat energy goes towards weakening or breaking hydrogen bonds rather than increasing kinetic energy

  3. Water acts as a buffer against rapid temperature changes

  4. Water is a habitat for aquatic organisms

  5. Ice is less dense than liquid water, so it floats and acts as a habitat for organisms

  6. Ice insulates the water below and prevents it from freezing

  7. Water has a high latent heat of vaporization, allowing organisms to cool themselves without losing much water
• Heat energy goes towards weakening or breaking hydrogen bonds


  Instead of increasing the kinetic energy of water molecules
• Ice is less dense than liquid water


  Ice floats and acts as a habitat for organisms
• Ice insulates the water below and prevents it from freezing


  Allowing organisms to continue living in the water under the ice
• Water has a high latent heat of vaporization


  Allows organisms to cool themselves without losing much water