Water Flashcards
What shape is water? What charges are on the molecules?
-Linear molecule w a bent shape - asymmetric distribution of electron density
-Highly electronegative oxygen pulls the electrons closer and gains partial neg charge so hydrogen has partial pos charge
-Unequal charge so considered polar
What are hydrogen bonds?
Strong dipole-dipole or charge-dipole interactions between a covalently cound hydrogen and lone pair of electrons
-Involve 2 electronegative atoms - nitrogen and oxygen
What does the possible 4 H-bonds per water molecule give water?
-Unusually high boiling point
-Uncharacteristically high melting point
-Unusually large surface tension
What is water a good or bad solvent for?
Good solvent for charged and polar sunbstances e.g amino acids and peptides, small alcohols, carbs
Poor solvent for nonpolar substances e.g nonpolar gases, aromatic moieties, aliphatic chains
Whta does the hydrophobic effect refer to and what is this a main factor behind?
Refers to the interaction of nonpolar molecules or components of molecules in aqueous solution
Main factors behind
-protein folding
-protein-protein association
-formation of lipid micelles
-binding of steroid hormones to their receptors
Does water surrounding nonpolar solutes have lower or higher entropy?
Low entropy
-This is thermodynamically unfavourable thus hydrophobic solutes have low solubility
What can occur with high enough concentrations of amphipathic molecules?
Complete aggregation into micelles - polar group on outside which can interact w water and non polar on the inside
Colligative vs non colligative properties
Colligative - boiling point, melting point, osmolarity - do not depend on nature of solute just concentration
Non colligative properties - viscosity, surface tension,taste, colour - depend on chemical nature of solute
What happens if a cell is in a hypertonic solution?
-Water moves out and cell shrinks
What happens if cell is in a hypotonic solution?
Water moves in, creating outward pressure, cell swells and may burst
What is the auto-ionization of water?
When hydrogen ions are spontaneously generated in pure water by dissociation (ionisation) of a small percentage of water molecules.
-dissociation of water is a rapid reversible process
What way can O-H bonds dissociate?
O-H bonds are polar amd can dissociate hetero-lytically
-Products are a proton and a hydroxide ion
What does the extent of water dissociation depend on?
Temperature
What happens proton ions in solution?
-Do not exist free in solution so rapily hydrated to form hydronium ions
What is a hydronium ion?
A water molecule w a proton associated w on eof the non-bonding electron pairs
