Exam 1 - Ch. 2, 3

Question 1

If you increase pH what happens to [H+] ?

Answer 1

increase pH, decrease [H+]

Question 2

if you decrease pH, what happens to [H+]?

Answer 2

decrease pH, increase [H+]

Question 3

if you decrease pH, what happens to molecule charge density?

Answer 3

decrease pH, increase + charge density

Question 4

if you increase pH, what happens to molecule charge density?

Answer 4

increase pH, increase - charge density

Question 5

pH < pKa , [HA] ? [A-]

Answer 5

[HA] > [A-]

Question 6

pH > pKa , [HA] ? [A-]

Answer 6

[HA] < [A-]

Question 7

pH = pKa , [HA] ? [A-]

Answer 7

[HA] = [A-]

Question 8

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)

Answer 8

When pH is more than 3 units away from pKa

Question 9

what is the pI?

Answer 9

Isoelectric point - the pH at which the overall formal charge on the molecule is zero

Question 10

what is a Zwitterion?

Answer 10

a species with both + and - charge and a formal charge of zero

Question 11

how to calculate pI with only pKa?

Answer 11

average the 2 pKas that include the isoelectric species as part of their respected HH equations

Question 12

Are proteins soluble close to their pI?

Answer 12

No- they are least soluble at a value close to their pI because they aggregate

Question 13

pH < pI - net charge + or - ?

Answer 13

pH < pI –> net + charge

Question 14

pH > pI - net charge + or - ?

Answer 14

pH > pI –> net - charge

Question 15

pH = pI - net charge?

Answer 15

pH = pI –> net charge = 0

Question 16

if delta G is negative, is the rxn favorable or unfavorable?

Answer 16

favorable

Question 17

if delta G is positive, is the rxn favorable or unfavorable?

Answer 17

unfavorable

Question 18

What does it mean if delta G = 0?

Answer 18

the rxn is at equilibrium

Question 19

what is the mass action expression for the following rxn : aA + bB –> cC + dD

Answer 19

Q = ( [C] ^c * [D] ^d ) / ( [A] ^a * [B] ^b )

Question 20

How do you drive an unfavorable rxn forward?

Answer 20

Couple it to a favorable rxn (delta G < 0)

maintain the ratio of [prod]/[react] BELOW the equilibrium value

Question 21

Q < Keq , what is the value of delta G?

Answer 21

delta G < 0 (favorable)

Question 22

Q > Keq, what is the value of delta G?

Answer 22

delta G > 0 (unfavorable)

Question 23

is delta S conf (conformational entropy) from U –> F favorable or unfavorable? is it + or -?

Answer 23

unfavorable, (-) , will increase + character of delta G

Question 24

is delta S solvent (solvent entropy) from U –> F favorable or unfavorable? is it + or -?

Answer 24

favorable, (+) , will increase - character of delta G

Question 25

what is a clathrate?

Answer 25

ice-like lower entropy structures that surround non-polar surface areas

Question 26

why is delta S solvent favorable for U –> F?

Answer 26

because the clathrates must be broken, which releases water molecules into the bulk solvent, increasing the entropy

Question 27

what does delta H (enthalpy) depend on?

Answer 27

Primarily, the # and kinds of bonds made and broken going from the initial to final state

Question 28

Generally, what is delta H for U –> F?

Answer 28

generally, delta H < 0

Question 29

what is Enthalpy (H)?

Answer 29

the heat exchanged btwn the system and surroundings at a constant pressure

Question 30

What does W stand for in S = Kb ln (W)

Answer 30

Number of microstates, i.e. the number of ways you can describe the arrangements of particles or energy within the system

Question 31

What are the 3 main types of non-covalent interactions in biomolecules?

Answer 31

van der waals, charge charge (ionic) and hydrogen bonds

Question 32

What are the features of the biochemical standard state?

Answer 32

all solutes except H+ ion are normalized to 1M in the Mass Action Expression

water is assigned an activity of 1 in the MAE

Question 33

What do buffers do?

Answer 33

they resist pH change following the addition of an acid or base within about +/- 1 pH unit of the pKa of the “buffer salt”

Question 34

what pH are most cells buffered at?

Answer 34

pH = 7.4

Question 35

define homeostasis

Answer 35

a set of conditions (temp, pH, concentration of ions/metabolites) occurring in cellular systems (living organisms)

Question 36

in a coupled reaction, which is considered the acceptor, and which is considered the donor?

Answer 36

acceptor is the rxn with the electrons on the reactant side
donor is the rxn with the electrons on the product side

Question 37

How do you calculate delta E?

Answer 37

Acceptor - Donor