2.2:BIOLOGICAL MOLECULES

• Biological molecules contain carbon hydrogen and oxygen
• Water is a polar molecule due to uneven distribution of charge
• Hydrogen bonds are weak bonds form between hydrogen and oxygen
• the four key properties of water are water as a solvent, water as a transport medium, water has a coolant and water as a habitat
• Polar molecules or charged molecules dissolve readily in water as water is a polar molecule making it a good solvent
• Polar substances dissolve and are easily transported in water around animals and plants either in the blood of animals or the xylem of plants making water a good transport medium
• Cohesion is water molecules sticking together by hydrogen bonds
• due to cohesion when water moves up the xylem it is as a continuous column of water
• water has a high specific heat capacity this means lots of energy is required to increase the temperature of water this is due to the energy required to break the hydrogen bonds between molecules
• Water having a high specific heat capacity is an advantage as the internal temperature of organism stays relatively constant this is important so the enzyme do not denature or reduce in activity
• water has a large latent heat of evaporation this means a lot of energy is required to convert water into a gas this is due to the energy required to break the hydrogen bonds between water molecules
• Water having a large latent heat of evaporation is an advantage as it is good for cooling in animals through sweating
• cohesion provides a surface tension on water this provides animals like small invertebrates a habitat
• water buffers temperature meaning it provides a stable environment for aquatic organisms