Biological molecules

Question 1

What are the functions of water

Answer 1

• Reactant in chemical reactions e.g. hydrolysis
• Solvent, most biological reactions take place in solution
• Transports substances like glucose and oxygen around plants and animals
• Helps with temperature control due to high specific heat capacity and high latent heat of evaporation
• Habitat for many organisms

Question 2

Describe the structure of water

Answer 2

• Water is a polar molecule – has regions of negativity and regions of positivity
• Water molecules bond together by H bonds between a slightly positive hydrogen on one water molecule and slightly negative oxygen on another water molecule

Question 3

What are the properties of water

Answer 3

• High specific heat capacity: H bonds absorb a lot of energy so takes a lot of energy to heat up
• High latent heat of evaporation: takes a lot of energy to break H bonds so a lot of energy is used up when H2O evaporates (sweat cools you down)
• Cohesive: very cohesive as polar so helps water flow for transport
• Low density when solid: Water molecules held far apart in ice lattice so less dense – floats on lakes and ponds insulating water below to maintain temperature as stable habitat
• Good solvent: water’s polar so attracts oppositely charged ions so the ions will be completely surrounded by H2O and dissolve