New Biology Revision

• Water


  Dipolar molecule with slight positive charge on hydrogen atoms and slight negative charge on oxygen atom

  
• Water


  • Excellent solvent
  • High surface tension
  • High latent heat of vaporization
  • High specific heat capacity
  • Unusual density properties
• Water is a covalent compound of hydrogen and oxygen

  
• Hydrogen bonding


  Bonds that form between water molecules

  
• Hydrogen bonding in water


  Leads to high melting and boiling point
• Polarity of water molecule

  Oxygen has partial negative charge, hydrogen has partial positive charge

  
• Water is a polar molecule with opposite ends having opposite charges

  
• Universal solvent


  Almost all substances can dissolve in water due to its dipolar nature
• Substances that can dissolve in water


  • Polar or ionic substances
  • Non-polar substances forming colloids, emulsions or suspensions

  
• Dissolving sodium chloride in water


  Positive and negative ions separate and become surrounded by water molecules

  
• Importance of water's dipolar nature for living organisms


  • Ability to form hydrogen bonds
  • Ability to dissolve and transport polar molecules
  • Cohesion and adhesion leading to high surface tension
  • High specific heat capacity and latent heat of vaporization helping maintain temperature

  
• High surface tension


  Property of liquid where it behaves like a stretched membrane, due to hydrogen bonding

  
• Importance of high surface tension


  • Enables some animals to stand, walk or run on water
  • Provides excellent capillary action
• Latent heat of vaporization


  Amount of heat energy needed to convert 1kg of water to vapour at constant temperature
• Importance of high latent heat of vaporization


  • Makes water a good coolant
  • Helps stabilize temperatures in organisms and bodies of water
  • Prevents overheating
• Latent heat of fusion


  Amount of heat energy needed to convert 1kg of ice into water or water into ice at constant temperature
• Importance of high latent heat of fusion


  • Ensures water bodies don't freeze easily in cold climate
  • Prevents cytoplasm from freezing at low temperatures
• Density and freezing properties of water


  • Most dense at 4°C, contracts until 4°C, then expands from 4°C to 0°C
  • Ice is less dense than water and floats
• Importance of water's density and freezing properties


  • Prevents water from freezing from the bottom up
  • Allows aquatic organisms to live underneath ice
• Specific heat capacity of water


  Amount of heat energy needed to increase temperature of 1kg of water by 1°C (4200J/kg)
• Importance of high specific heat capacity


  • Prevents sudden fluctuations in temperature of aquatic environments
  • Helps organisms maintain steady internal temperature
• Water is an effective molecule for transporting other molecules around living organisms
• Water is a solvent
• Water is slightly charged/dipolar
• Polar molecules can dissolve in water by forming hydrogen bonds

  
• Cohesion and adhesion lead to high surface tension which helps in plant transport
• Water as a liquid assists in mass flow
• Dipolar


  Having a slight positive charge at one end and a slight negative charge at the other end
• Solvent


  A substance that can dissolve other substances
• Hydrogen bonds


  Bonds that form between water molecules

  
• Latent heat of vaporization


  Amount of heat energy needed to convert 1kg of liquid to its vapour state at constant temperature
• Specific heat capacity


  Amount of heat energy needed to increase the temperature of 1kg of a substance by 1°C
• Glycogen


  Not coiled
• Amylose


  • Has only 1,4 glycosidic bonds
• Glycogen


  • Has 1,4 and 1,6 glycosidic bonds
• Difference between a monosaccharide and a polysaccharide
• Difference between the structure of lactose and the structure of starch
• Starch


  Composed of glucose only
• Lactose


  Composed of glucose and galactose
• Starch


  • Has 1,4 and 1,6 glycosidic bonds