Module 2 Flashcards
2 characteristics of water
- most abundant
- passive + active roles
passive role
forms structure in response to interaction with water
active role
water is a participant
O2 structure
- more electronegative than H+
- partial negative charge
does water have a permanent or non-permanent dipole?
permanent because of its electronegativity
what charge does Hydrogen have
partial positive
what do dipoles influence (2)
- the ability to form electronegative interactions with charged molecules
- the ability to form hydrogen bonds
what are amphipathic molecules?
have both polar and non-polar portions
what are hydrogen bonds
electrostatic interactions between an electronegative atom with H+ covalently bonded to another electronegative atom with free electron pair (O2 or N2)
Are Anti-parallel or parallel beta sheets more stable?
more stable than parallel sheets due to better geometry of H+ bonds
unique abilities of O2/N2
can serve as electron donors & acceptors
what is a H+ bond donor?
electronegatively charged atom that has H+ covalently attached
How many H+ bonds can H2O molecules form?
4 H+ bonds (2 acceptors, 2 donors)
advantage of H+ bonds between H2O molecules
confer great internal cohesion
how many H+ bonds does liquid H2O have?
3-4
what does electronegative mean?
an atom’s tendency to attract electrons to itself
what does permanent dipole mean?
uneven distribution of charge
what does Van der waals forces mean?
interaction between permanent + induced dipoles
when is attraction at its max in van der waals forces?
when 2 atoms are separated by the sum of radii
what is the hydrophobic effect?
polar groups interact with water and non-polar regions away from water
non-polar compounds dissolve ( ) in water
poorly
non-polar side chains
form away from water
polar side chains
on surface, away from water
how do strong acids/bases dissociate in water?
they fully dissociate in water
what does the folding of a polypeptide do to entropy?
decrease polypeptide entropy & increase water entropy
what does the association of non-polar molecules do to entropy?
increase entropy
true or false: H2O molecules around hydrophobic molecules are more ordered than pure water
true, because the introduction of non-polar molecule causes a decrease in entropy
what is a titration curve?
the ratio of acid to its conjugate base changes over the curve
what does a lower PKa value mean?
a stronger acid
what does it mean when pH=PKa?
system is best ale to resist changes
what form of the molecule is above the buffer region?
un-protonated (already donated the proton)
what form of molecule is below the buffer region?
protonated (has not donated the proton yet)
what is the Henderson-Hasselbalch equation?
pH=PKa + log [A-] / [HA]
what is a buffer?
a solution that resists changes in pH caused by the addition of an acid or base
what does a buffer consist of?
a weak acid + conjugate base
what is an amphoteric molecule?
can serve as an acid or base (a molecule capable of donating and accepting protons)
ionization of water equation
Keq= [H+] [OH-] / [H2O]
which 2 functional groups undergo attractive electrostatic interactions?
carboxyl & guanidino
hydrophilic molecules are…
polar (water loving)
hydrophobic molecules are…
non-polar (water fearing)
a hydrogen bond between a carbonyl & water molecule, the hydrogen atom is ( ) to the carbonyl group and ( ) to the oxygen of the water molecule
electrostatic associated, covalently linked
