water and inorganic ions

• dipolar molecule - oxygen atom has slightly negative charge and hydrogen atom has slightly positive charge
• due to its dipole nature, water molecules can form hydrogen bonds with other water molecules (delta +ve hygrogen attracted to delta -ve oxygen)
• water has a high specific heat capacity

  • takes more energy to heat a given mass of water
  • water can act as a buffer against sudden temperature variations
  • organisms are mostly water, so it buffers them against sudden temperature changes
• high latent heat of vaporisation

  • lot of energy needed to evaporate 1 gram of water
  • effective means of cooling, as body heat is used to evaporate water
• cohesion and surface tension

  • large cohesive forces, allows it so be pulled up through a tube (xylem)
  • surface tension is strong enough to support small organisms (habitats)
• water in metabolism

  • used to break down complex molecules (hydrolysis)
  • produced in condensation reactions
  • chemical reactions take place in aqueous mediums
  • water is raw material in photosynthesis
• water as a solvent

  • dissolve oxygen and carbon dioxide
  • dissolves wastes such as urea and ammonia
  • dissolves inorganic phosphates and hydrophilic molecules
• iron ions :

  • found in haemoglobin, where they play a role in the transport of oxygen
• phosphate ions:

  • structural role in DNA
  • role in storing energy in ATP
• hydrogen molecules:

  • important in determining the pH of solutions and therefore the functioning of enzymes
• sodium ions:

  • used in the transport of glucose and amino acids across plasma membranes (co-transport)