1B - Water Flashcards
How much of a cell is water?
80%
What are the properties of water?
Metabolite Solvent High latent heat of vaporisation High specific heat capacity Cohesive
How does water being a metabolite help living organisms?
Used in metabolic reactions including condensation and hydrolysis reactions keeping the organism alive.
Hydrolysis requires water when a bond is broken and condensation release water as a new bond is formed.
E.g. Amino acids are joined in a condensation reaction to form polypeptides. Energy from ATP is released through as hydrolysis reaction.
How does water being a solvent help living organisms?
Substances can dissolve in it and most metabolic reactions take place in solution (e.g. the cytoplasm).
How does water having a high latent heat of vaporisation help living organisms?
Helps with temperature control - use water loss through evaporation to cool down (sweat), without losing too much water.
Takes a lot of energy to break the hydrogen bonds between water molecules so a lot of water is used up when water evaporates.
What does it mean if water is cohesive?
The water molecules stick together which helps water transport in plants as well as transport in other organisms.
Describe the structure of water
1 molecule = 2 H atom and 1 O atom.
Because the shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of each hydrogen is left with a slightly positive charge.
The unshared negative electrons on the oxygen atom give a slightly negative charge.
This makes water a polar molecule as it has a partial negative charge on one side and a partial positive charge on the other.
The slightly negatively-charged oxygen atoms attract the slightly positively-charged hydrogen atoms of other water molecule.
This attraction is called hydrogen bonding.
How can water buffer (resist) changes in temperature?
The hydrogen bonds can absorb a lot of energy.
So water has a high specific heat capacity - it takes a lot of energy to heat it up.
Means that water doesn’t experience rapid temperature changes making water a good habitat because the temperature underwater is likely to be more stable than on land. Also means inside organisms the temperature remains pretty stable - helping to maintain a constant internal body temperature.
Why is water a solvent?
Most metabolic substances (reactants) are ionic and because water is polar this means the ions will get totally surrounded by water molecules and they’ll dissolve.
What does strong cohesion mean for water?
Water has a high surface tension.
