2: Water Flashcards
most abundant compound in organisms (70% of body weight)
water
molecular geometry of water
bent or V-shaped (nearly tetrahedral arrangement of four electron groups around O)
how many hydrogen bonds can each water molecule make?
4 (2 on oxygen, 1 on each hydrogen)
8 unique properties of water that sustain life on Earth
high cohesion
high adhesion
high surface tension
high specific heat
high heat of vaporization
liquid at room temperature
excellent solvent
hydrophobic exclusion
act of sticking together
cohesion
act of sticking to something (due to ability of water to form H bonds)
adhesion
what component of plant cell walls can form H bonds with water molecules, allowing the latter’s transport?
cellulose (the hydroxyl groups)
measure of the resistance of a substance to increase its surface area due to high cohesion of its molecules
surface tension
2 types of molecules in a sample of water
inner and surface
explain the high surface tension in water
there is formation of stronger bond between surface water molecules as they are pulled inward by a net inward force due to absence of attractive force acting from above and thus preventing them from being stretched or broken
2 importance of high surface tension of water
- allows denser things and animals to float
- formation of water droplets
amount of heat per unit mass required to raise the temperature by 1degree Celsius
specific heat
specific heat of water
2 cal/g-degree Celsius
what happens when temperature of water increases? decreases?
increase in T: water molecules would move faster due to increase in kinetic energy, leading to the breaking of H bonds which absorbs heat
decrease in T: water molecules would move slower due to decrease in KE, causing the formation of H bonds which releases heat
2 importance of moderation of temperature by water
regulate air temperature change near oceans
regulation of internal body temperature
process at which as liquid evaporates, the liquid surface that remains behind cools down
evaporative cooling
what makes evaporative cooling possible
high heat of vaporization of water
amount of heat needed to turn 1 g of liquid into a vapor without a rise in temperature of the liquid
heat of vaporization
heat of vaporization of water
540 cal/g at 25 degrees Celsius (high due to hydrogen bonding)
2 importance of evaporative cooling
sweating
evaporation of water on the surface of leaves
how many hydrogen bonds does water molecules form on ice? on liquid water?
ice: 4 H bonds, stable
liquid water: 3.2 H bonds on average, constant breaking and reformation of H bonds
ice is ____ than water
less dense
why does water readily dissolve other polar compounds and salts?
high dielectric constant
measure of the ability of a solvent to keep opposite charges apart
dielectric constant
refers to when ions are nonrandomly surrounded by water molecules that attenuates the coulombic forces between these ions
hydration
tendency of amphiphiles to self-associate in water than to dissolve individually
hydrophobic effect
why do amphiphile molecules cluster together instead of each amphiphile molecule being surrounded by water molecules?
the latter is not favored because of the resulting highly ordered structure (decrease in entropy of the system) and the former also requires fewer water molecules
spherical amphiphilic structures that have a hydrophobic core and a hydrophilic shell
micelles
3 instances of water as medium for biochemical processes
weak interactions in the aqueous system
water and its ionization products (H3O+ and OH-)
weak acid-base equilibria/physiological buffers
4 weak interactions of water in aqueous systems that are individually weak but are collectively significant
hydrogen bonding
ionic interactions
hydrophobic interactions
van der Waals forces
4 examples where H bonds are found in biological systems
between alcohol and water
between carbonyl ketone and water
between peptide groups
between nitrogenous bases
bond between nucleic acids
phosphodiester bond
