Lecture 3: Water Flashcards
linear
sequence of the nucleotide residues in a strand of DNA is maintained
by _____ bonds (covalent or ionic
covalent
the double helix structure of DNA is stabilized by ___
interactions between different parts of the molecule
noncovalent
every
kind of protein is made up of amino acids linked by ___
bonds
covalent peptide
Why is water unique?
the strong tendency of water molecules to form hydrogen bonds with other water molecules
what are the roles of the 6 electons in the outer orbital of oxygen atom in water?
two are involved in covalent bonds to the hydrogen atoms.
The other four electrons exist in nonbonded pairs, which are excellent hydrogen-bond acceptors.
vaporization of water
requires __ amount of energy for a molecule of its size
large
true or false: Only the boiling point not the heat of vaporization of water are therefore remarkably high
false: Both the heat of vaporization
and the boiling point
What is heat capacity?
Heat capacity is a measure of
the energy that must be added to raise (or removed to lower) the temperature of a substance by 1 °C
Ice is a molecular lattice
formed by indefinite repetition of a
___ pattern.
tetrahedral hydrogen-bonding
Why is ice’s density is low?
Because of the length of the hydrogen
bonds, the structure is a relatively
open one, which accounts for the low
density of ice.
Each molecule in a tetrahedral lattice in ice is hydrogen-bonded to how many other molecule?
four
The structure of liquid water has been described as ____ of hydrogen bonds
“flickering clusters”
Why is the liquid phase of water more dense than the solid phase of water?
the liquid phase of water is more
dense than its solid phase because when the lattice breaks down,
molecules can move closer together.
Does water have high viscosity? What is viscosity?
Yes; it is the resistance to flow
Does water have high surface tension? What is surface tension?
Yes, it is the resistance of a liquid surface to distortion or penetration).
Does water have high dielectric constant? What is it effect/what does it do?
Yes. It lowers electrostatic interaction between cations and anions.
Water is a good solvent because
its tendency to
form hydrogen bonds and
its polar character.
What are hydrophilics?
water-loving
Is water is an excellent solvent for
ionic compounds?
Yes
Explain how water dissolves salt
The interactions of the negative ends of the water dipoles with cations and the positive ends of water dipoles with anions
in aqueous solution cause the ions to become hydrated, that is, surrounded
by shells of oriented water molecules called hydration shells
What are hydrophobics?
water-fearing
Hydrophilic forms ___, while hydrophobic forms ___ in water
hydration shell, clathrate
Clathrate formation corresponds to ____, which is unfavorable in nature
decrease in entropy or randomness of mixture
Explain what the hydrophobic effect is
Surrounding
two hydrophobic molecules with two separate cages requires
more ordering of water in clathrates than surrounding both
hydrophobes within a single cage. Thus, the hydrophobic molecules
tend to aggregate, because doing so releases some water molecules
from the clathrates, thereby increasing the entropy of the solvent.
What are amphipathic molecules?
they have both hydrophobic and hydrophilic properties
Amphipatic have ___- head and ____ tail
hydrophilic; hydrophobic
