Exam 1 - Ch. 2, 3 Flashcards
If you increase pH what happens to [H+] ?
increase pH, decrease [H+]
if you decrease pH, what happens to [H+]?
decrease pH, increase [H+]
if you decrease pH, what happens to molecule charge density?
decrease pH, increase + charge density
if you increase pH, what happens to molecule charge density?
increase pH, increase - charge density
pH < pKa , [HA] ? [A-]
[HA] > [A-]
pH > pKa , [HA] ? [A-]
[HA] < [A-]
pH = pKa , [HA] ? [A-]
[HA] = [A-]
when is the difference in pH and pKa negligible? (i.e. you can say it is FULLY deprotonated/protonated, charge will be 0, +1 or -1)
When pH is more than 3 units away from pKa
what is the pI?
Isoelectric point - the pH at which the overall formal charge on the molecule is zero
what is a Zwitterion?
a species with both + and - charge and a formal charge of zero
how to calculate pI with only pKa?
average the 2 pKas that include the isoelectric species as part of their respected HH equations
Are proteins soluble close to their pI?
No- they are least soluble at a value close to their pI because they aggregate
pH < pI - net charge + or - ?
pH < pI –> net + charge
pH > pI - net charge + or - ?
pH > pI –> net - charge
pH = pI - net charge?
pH = pI –> net charge = 0
if delta G is negative, is the rxn favorable or unfavorable?
favorable
if delta G is positive, is the rxn favorable or unfavorable?
unfavorable
What does it mean if delta G = 0?
the rxn is at equilibrium
what is the mass action expression for the following rxn : aA + bB –> cC + dD
Q = ( [C] ^c * [D] ^d ) / ( [A] ^a * [B] ^b )
How do you drive an unfavorable rxn forward?
Couple it to a favorable rxn (delta G < 0)
maintain the ratio of [prod]/[react] BELOW the equilibrium value
Q < Keq , what is the value of delta G?
delta G < 0 (favorable)
Q > Keq, what is the value of delta G?
delta G > 0 (unfavorable)
is delta S conf (conformational entropy) from U –> F favorable or unfavorable? is it + or -?
unfavorable, (-) , will increase + character of delta G
is delta S solvent (solvent entropy) from U –> F favorable or unfavorable? is it + or -?
favorable, (+) , will increase - character of delta G