Properties of water (Dr.Miles TAMU) Flashcards
What type of geometry is water and what other properties does it have?
- Tetrahedral and is SP^3 hybridized
- bent
- gives dipole moments
Mutual reinforcement
The formation of the first hydrogen bond facilitates the second which upon forming facilitates forming the third which facilitates making the fourth. Thus the formation of hydrogen bonds is cooperative.
What makes ice have a low density
Each water molecule acts as a donor for two H-bonds and as acceptors for two more. This causes an open structure
Why are ionic salts soluble in water
Dipoles of water interact with cations and anions causing these ions to be hydrated which means surrounded by water molecules in hydration shells
What charges can water solvate and how do the lone pairs do this?
both positive and negative
-Water orients its lone pairs of electrons towards positive charges and orients the partially positive hydrogens at negative charges (greater charge greater solubility)
Water is an excellent solvent for
-Polar molecules (through hydrogen bonding)
-Ionic salts
compounds with _____(7) are soluble in water
-hydroxyl group
- amines
- sulfhydryls
- carboxylates
-esters
- ketones
- amides
Clathrate structure
When hydrophobic molecules dissolve into solution, water molecules form an ice like hydrogen bonding lattice
- causes a decrease in the entropy thus creating low solubility
Amphiphiles
hydrophilic part and a hydrophobic part such as fatty acids and detergents. They have polar heads such as a carboxylate or phosphate group and a hydrophobic tail of hydrocarbons. The hydrophobic tails are caged in clathrate structures.
Micelle formation
hydrophobic alkyl chains are sequestered in the inside of the micelle.
- this frees ordered water molecules thus increasing entropy
hydrophobic interactions
forces that hold the nonpolar regions of the molecules together out of the aqueous solvent
- entropy driven
- drive globular protein folding, DNA double helix formation and membrane formation
Colligative properties of aqueous solutions: Dissolved solutes….
- alter the physical properties of water
- lower the freezing point of water
- raise the boiling point of water
- impose local order of the water molecules surrounding them (difficult to arrange themselves in crystalline lattice or escape)
How do dissolved solutes alter colligative properties of aqueous solutions
lower the effective concentration of water
osmosis
Water molecules moving spontaneously from a region of high concentration to the region of low concentration
biological membranes are _____ to water but _____ to ions and large polar molecules
permeable, impermeable
isotonic
Solutions separated by a semipermeable membrane that are of equal molar concentration of solute
- no net movement of water across the membrane
hypertonic
solution surrounding the semipermeable membrane has a higher molar concentration of solute than the solution inside of the membrane
- Water will rush out of the cell
hypotonic
If the solution surrounding the semipermeable membrane has a lower molar concentration of solute than the solution inside of the membrane
- water will rush into the cell creating outward pressure causing the cell to swell and burst
how do Bacteria and plants prevent osmosis catastrophes
Rigid cell walls of sufficient rigidity to resist osmotic pressure and prevent osmotic lysi
how do Protozoa’s prevent osmosis catastrophes
a vacuole that pumps water continually out of the cell
how do multicellular animals prevent osmosis catastrophes
blood plasma and the extracellular fluids of tissues are maintained at an osmolarity close to that of the cytosol of cells. Cells continually pump sodium ions out of the cytosol into the plasma to maintain osmotic balance
turgor pressure
very high solute concentration in their vacuole which produces osmotic pressure
- helps draw water into plant cells
