3.2 - Water Flashcards
How do hydrogen bonds form between water molecules?
• water is polar, O is more electronegative than H so attract electron density in a covalent bond more strongly
• forms O delta negative and H delta positive
• there are intermolecular forces of attraction between a lone pair on O delta negative of one molecule & hydrogen delta positive on an adjacent molecule
State 7 biologically important properties of water
• reaches maximum density at 4°c
• high surface tension
• incompressible
• metabolite solvent for chemical reactions in the body
• high specific heat capacity
• high latent heat of vaporisation
• cohesion between molecules
Why is the incompressible nature of water important for organisms?
• provides turgidity to plant cells
• provides hydrostatic skeleton fot some small animals eg. Earth worms
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 the high surface tension of water important for organisms?
• slows water loss due to transpiration in plants
• water rises unusually high in narrow tubes lowering demand on root pressure
• some insects can skim across the surface of water
Why are the high specific heat capacity and latent of vapourisation of water important for organisms?
• acts as a temperature buffer which enables endothermic to resist fluctuations in core temperature to maintain optimum enzyme activity
• cooling effect when water evaporates from skin surface as sweat/ mouth when panting
Define monomer and give a example
•monomer = smaller units that join together to form larger molecules
•Eg. Monosaccharides ( glucose, fructose, galactose, ribose )
• amino acids
• nucleotides
Define polymer and give examples
•Polymer = molecules formed when many monomers join together
• polysaccharides
• proteins
• DNA/RNA
What happens in condensation and hydrolysis reactions?
• condensation- chemical bond forms between 2 molecules and a molecule of water is produced
• hydrolysis- water molecule is used to break a chemical bond between 2 molecules eg. Peptide bonds in protein,
Ester bonds between fatty acids and glycerol in lipids
What is a transport medium and give a example
Water is a transport medium and transports substances such as glucose and oxygen
What is specific heat capacity?
Amount of thermal energy required to rise the temperature of 1Kg of a substance by 1°c
What is waters specific heat capacity
4200 J/kg °c
Why is waters specific heat capacity so high ?
• many hydrogen bonds - takes a lot of thermal energy to break these bonds and a lot of energy to build them thus the temperature of water does not fluctuate greatly
