Water (3.1.7)

Question 1

what is water?

Answer 1

a major component of cells

Question 2

what are they key properties of water?

Answer 2

1. metabolite in many metabolic reactions
2. important solvent in which metabolic reactions occur
3. relatively high specific heat capacity
4. relatively large latent heat of vaporisation
5. strong cohesion between water molecules

Question 3

properties of water - metabolite?

Answer 3

breaks down complex molecules during hydrolysis reactions
produced in condensation reactions

Question 4

properties of water - solvent?

Answer 4

dissolves substances like:
gases eg. CO2
waste products eg. urea
enzymes
inorganic ions and small hydrophilic molecules

Question 5

properties of water - specific heat capacity?

Answer 5

large amounts of energy are needed to increase temperature of 1g of water by 1 degree celsius due to hydrogen bonding between molecules
means it is a liquid at most temperatures on Earth, so life can exist
allows it to buffer changes in temperature

Question 6

properties of water - latent heat of vaporisation?

Answer 6

large amounts of energy are needed to evaporate 1g due to hydrogen bonding between molecules
allows it to have cooling effect
eg. cools body down during exercise - water carries away lots of heat energy when it evaporates from the skin as sweat, cooling the body’s surface and lowering body temperature

Question 7

properties of water - cohesion and surface tension?

Answer 7

hydrogen bonding means water molecules have large cohesive forces (tendency to stick together)
this supports columns of water in the tube-like transport cells of plants ie. xylem
it also produces surface tension when water meets air (molecules have tendency to be pulled back into water body instead of escape from it)
surface tension allows water surface to support small organisms