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
what is a clathrate?
ice-like lower entropy structures that surround non-polar surface areas
why is delta S solvent favorable for U –> F?
because the clathrates must be broken, which releases water molecules into the bulk solvent, increasing the entropy
what does delta H (enthalpy) depend on?
Primarily, the # and kinds of bonds made and broken going from the initial to final state
Generally, what is delta H for U –> F?
generally, delta H < 0
what is Enthalpy (H)?
the heat exchanged btwn the system and surroundings at a constant pressure
What does W stand for in S = Kb ln (W)
Number of microstates, i.e. the number of ways you can describe the arrangements of particles or energy within the system
What are the 3 main types of non-covalent interactions in biomolecules?
van der waals, charge charge (ionic) and hydrogen bonds
What are the features of the biochemical standard state?
all solutes except H+ ion are normalized to 1M in the Mass Action Expression
water is assigned an activity of 1 in the MAE
What do buffers do?
they resist pH change following the addition of an acid or base within about +/- 1 pH unit of the pKa of the “buffer salt”
what pH are most cells buffered at?
pH = 7.4
define homeostasis
a set of conditions (temp, pH, concentration of ions/metabolites) occurring in cellular systems (living organisms)
in a coupled reaction, which is considered the acceptor, and which is considered the donor?
acceptor is the rxn with the electrons on the reactant side
donor is the rxn with the electrons on the product side
How do you calculate delta E?
Acceptor - Donor
