Biological molecules

• What makes a molecule polar

  One end that is negatively charged and one that is positively charged
• What makes water so important to living organisms?

  • Excellent solvent
  • High specific heat capacity
  • High latent heat of vaporisation
  • Less dense when solid
  • High surface tension
  • Good adhesion and cohesion
  • Acts as a reagent
• what substances can dissolve in water?

  Covalently bonded polar substances
• why is water being a good solvent important?

  • Allows chemical reactions to occur within cells (dissolved substances are more reactive)
  • Metabolites can be transported efficiently
• why is water having a high specific heat capacity important?

  • A relatively large amount of energy is needed to raise its temperature (due to many hydrogen bonds)
  • Provides suitable habitats with a constant temperature (also important for enzyme activity).
  • Water in blood plasma and tissue fluid transfers heat around the body
• Why is water having a high latent heat of vaporisation important?

  • Large amount of thermal energy must be absorbed to change from liquid to gas (due to hydrogen bonds)
  • Little water is required to evaporate to lose a great amount of heat which provides a cooling effect eg in transpiration or sweat