BICH 410 EXAM 1 COMBINED SET
QUESTIONS WITH CORRECT
ANSWERS (GRADED A+)
water has a high dielectric constant - Answer- solvates polar groups well, attraction of
charges and partial charges responsible
Ions - Answer- like Na+ and Cl- are always hydrated in water, rapidly exchanging
*hydration shell* (dipole interactions)
water also forms h bonds with - Answer- polar, uncharged solutes
water dissociation constant - Answer- 10^-14
H2O --> H+ + OH-
proton jumping occurs rapidly, molecules in bulk water, 55.5M
acidity of a solution - Answer- pH = -log[H+]
acids ________ a proton
bases _________ a proton - Answer- donate, accept
dissociation constant - Answer- varies with the strength of an acid
Henderson-Hasselbalch equation - Answer- relates the pH of a solution of a weak acid
to the pK and the concentrations of the acid and its conjugate base (pH = pKa +
log[ratio])
A titration curve demonstrates that if the concentrations of an acid and its conjugate
base are close - Answer- the solution is buffered against changes in pH when acid or
base is added
many biological molecules contain ___________ so that they are sensitive to changes
in pH - Answer- ionizable groups
the small equilibrium constant, Keq, indicates - Answer- a negligible change in
concentration of bulk water as a consequence of ionization
pH is the negative log of the - Answer- hydrogen ion concentration
Keq for H20 = - Answer- 10^-14 M^2
, pKw = - Answer- 14 (pH + pOH)
HA - Answer- acid
A- - Answer- base
weak acids are - Answer- those with a significant concentration of both ionized (A-) and
protonated (HA), species in equilibrium
when [HA] = [A-], - Answer- pH = pKa
assume that at all times, - Answer- the total [A-] + [HA] = 1
y axis = - Answer- pH
buffers - Answer- solutions that resist changes in pH when limited amounts of acid or
base are added
Buffers can only be used reliably within - Answer- one pH unit of their pKa
Buffer action is a - Answer- continuous cycle of protonation and deprotonation, as long
as both [HA] and [A-] are present in abundance
they are both abundant at the pKa and up to one log of - Answer- [H+] (+/-1 pH unit) on
either side
buffers hold pH constant - Answer- to preserve activity
Watson and Crick - Answer- "We have discovered the secret of life!"
referring to replication
Rosalind Franklin - Answer- diffraction pattern photo of DNA
How is info stored in nucleic acids? - Answer- DNA
How many structures of nucleotides? - Answer- 5 different structures
Central Dogma - Answer- DNA (transcirption) --> RNA (translation)--> Protein
nitrogenous bases of nucleotides include 2 types of _________ and 3 types of
_________ - Answer- purines, pyrimidines
nucleotide consists of - Answer- 1. a nitrogenous base
2. a ribose or deoxyribose sugar
3. one or more phosphate groups
QUESTIONS WITH CORRECT
ANSWERS (GRADED A+)
water has a high dielectric constant - Answer- solvates polar groups well, attraction of
charges and partial charges responsible
Ions - Answer- like Na+ and Cl- are always hydrated in water, rapidly exchanging
*hydration shell* (dipole interactions)
water also forms h bonds with - Answer- polar, uncharged solutes
water dissociation constant - Answer- 10^-14
H2O --> H+ + OH-
proton jumping occurs rapidly, molecules in bulk water, 55.5M
acidity of a solution - Answer- pH = -log[H+]
acids ________ a proton
bases _________ a proton - Answer- donate, accept
dissociation constant - Answer- varies with the strength of an acid
Henderson-Hasselbalch equation - Answer- relates the pH of a solution of a weak acid
to the pK and the concentrations of the acid and its conjugate base (pH = pKa +
log[ratio])
A titration curve demonstrates that if the concentrations of an acid and its conjugate
base are close - Answer- the solution is buffered against changes in pH when acid or
base is added
many biological molecules contain ___________ so that they are sensitive to changes
in pH - Answer- ionizable groups
the small equilibrium constant, Keq, indicates - Answer- a negligible change in
concentration of bulk water as a consequence of ionization
pH is the negative log of the - Answer- hydrogen ion concentration
Keq for H20 = - Answer- 10^-14 M^2
, pKw = - Answer- 14 (pH + pOH)
HA - Answer- acid
A- - Answer- base
weak acids are - Answer- those with a significant concentration of both ionized (A-) and
protonated (HA), species in equilibrium
when [HA] = [A-], - Answer- pH = pKa
assume that at all times, - Answer- the total [A-] + [HA] = 1
y axis = - Answer- pH
buffers - Answer- solutions that resist changes in pH when limited amounts of acid or
base are added
Buffers can only be used reliably within - Answer- one pH unit of their pKa
Buffer action is a - Answer- continuous cycle of protonation and deprotonation, as long
as both [HA] and [A-] are present in abundance
they are both abundant at the pKa and up to one log of - Answer- [H+] (+/-1 pH unit) on
either side
buffers hold pH constant - Answer- to preserve activity
Watson and Crick - Answer- "We have discovered the secret of life!"
referring to replication
Rosalind Franklin - Answer- diffraction pattern photo of DNA
How is info stored in nucleic acids? - Answer- DNA
How many structures of nucleotides? - Answer- 5 different structures
Central Dogma - Answer- DNA (transcirption) --> RNA (translation)--> Protein
nitrogenous bases of nucleotides include 2 types of _________ and 3 types of
_________ - Answer- purines, pyrimidines
nucleotide consists of - Answer- 1. a nitrogenous base
2. a ribose or deoxyribose sugar
3. one or more phosphate groups
