Water Flashcards
How do hydrogen bonds form between water molecules?
Water is polar: O more electronegative than H, so attracts electron density in covalent bond more strongly.
Forms O d- (slightly negative) & H + (slightly positive).
There are intermolecular forces of attraction between a lone pair on O d- of one molecule & H d+ on an adjacent molecule.
Explain why ice floats on water. Why is this important for organisms?
Ice is less dense than water because H-bonds hold molecules in fixed positions further away from each other.
Insulates water in arctic climates so aquatic organisms can survive. Water acts as a habitat.
Why is water an important solvent for organisms?
Polar universal solvent dissolves & transports charged particles involved in intra & extracellular reactions e.g. PO
3-
4
for DNA synthesis.
Why are the high specific heat capacity and latent of vapourisation of water important for organisms?
Acts as a temperature buffer which enables endotherms to resist fluctuations in core temperature to maintain optimum enzyme activity.
Cooling effect when water evaporates from skin surface as sweat/ from mouth when panting.
What happens in condensation and hydrolysis reactions?
Condensation: chemical bond forms between 2 molecules & a molecule of water is produced.
Hydrolysis: a water molecule is used to break a chemical bond between 2 molecules e.g. peptide bonds in proteins, ester bonds between fatty acids & glycerol in lipids.
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