Energetics of Key Metabolic Steps

Question 1

Free energy change equation?

Answer 1

Concentrations must
be in molar units

RT log = 1.36 log

Question 2

As the substrate concentration increases relative to the product concentration, the log term will become more ____ and ΔG will become more ____.

Answer 2

log more negeative, ΔG more negative

Question 3

As the substrate concentration increases relative to the product concentration which way does the rxn proceed?

Answer 3

greater tendency to proceed from left to right

Question 4

standard free energy chain equals

Answer 4

Kʹ′eq is the ratio of products to substrates at equilibrium

Question 5

what is the TOTAL standard free energy chain

Answer 5

This relationship also holds for calculating ΔGT from ΔG for each step.

Question 6

When you reverse the direction for writing a reaction, you _____ the sign of the standard free energy change.

Answer 6

change

Question 7

how to to calculate the voltage difference between two half reactions?

Answer 7

ΔE°ʹ′ = E°ʹ′ (e- acceptor) - E°ʹ′ (e- donor)

The minus sign accounts for the fact that you are reversing the direction of one of the reactions to make it an oxidation. Don’t change the sign twice.

Question 8

The standard free energy change, from the voltage difference between two half reactions

Answer 8

ΔG°ʹ′ = -nFΔE°ʹ′

n is the number of electrons transferred, F = 23.063 kcal/mol•volt, ΔE°ʹ′

Question 9

the potential
difference in an oxidation reduction reaction

where reactants and products are not 1 M.

Answer 9

Question 10

as the concentration of substrates increase, ΔE ___

Answer 10

increases

Question 11

The actual free energy change can be calculated from

Answer 11

ΔG = -nFΔE

the voltage difference between two half reactions for conditions other than the standard state

Question 12

ΔG, the actual free energy change which can be measured for a reaction running from left to right under a ____ conditions

Answer 12

given set of conditions

Question 13

ΔG°, the free energy change under some ___ conditions

Answer 13

standard

Question 14

Why is ΔG° useful?

Answer 14

Can calculate ΔG under any conditions if ΔG° is known.

Question 15

To convert kcal/mol to kjoules/mol multiply by

Answer 15

4.18 kJ/kcal.

Question 16

Standard State

∆G = ∆G°, when

Answer 16

[subst] and [prod] = 1 M

Question 17

all spontaneous reactions have a

Answer 17

negative free energy change

Question 18

biochemests standard state

if water is a product or substrate it is defined as

Answer 18

55.5 M = H20

Question 19

biochemests standard state

if H+ is a product or substrate it is defined as

Answer 19

Question 20

atp hydrolysis

what is the free energy change equation?

Answer 20

Question 21

ΔG = 0, the reaction has no tendency for

Answer 21

net reaction in either direction

Question 22

A to C free energy change?

Answer 22

ΔG°ʹ′1 + ΔG°ʹ′2 = -1.36 log Kʹ′eq(1) –1.36 log Kʹ′eq(2)

= -1.36 log (Kʹ′eq(1) x Kʹ′eq(2))

Question 23

A to C?

Answer 23

Question 24

Cannot use ΔG to predict ΔG at a___

Answer 24

catalytic site

the environemnt may be different here

Question 25

ΔG = ΔG°ʹ′ + 1.36 log P/S. If a reaction with a (+)ΔG°ʹ′ is to proceed
as written, the ratio of P/S under physiological conditions must be small enough to

Answer 25

result in a negative term which more than offsets the positive ΔG°ʹ′

• in a coupled pathway with a net negative ΔG, the concentrations of substrates will adjust so that all steps have a negative ΔG.*

Question 26

in a coupled pathway with a net negative ΔG, the concentrations of substrates will adjust so that

Answer 26

all steps have a negative ΔG.

since P/S has to be small enough

Question 27

how does malate to OAA be spontaneous with a standard free energy thats positive

Answer 27

get a P/S small enough to make the actual free energy change to be negative

Question 28

redox

electron transfer often occurs via the transfer of

Answer 28

hydrogen atoms

Question 29

redox half reaction

Answer 29

The affinity of A for an e- can be measured as the pressure on an e- to flow to A or from AH2 compared to a standard half-reaction.

Question 30

For a redox reaction, the solvent does not normally supply electrons so

Answer 30

two half- reactions must be combined, one as a reduction reaction and one as an oxidation.

Question 31

half reactions are always written in the direction of

Answer 31

REDUCTION

Question 32

The affinity of an e- acceptor for an electron is measured relative to a reference:

Answer 32

The standard hydrogen cell.

Question 33

if e-‘s tend to flow to the right, the E° is

Answer 33

positive

Question 34

The more positive the standard reduction potential the greater the___

Answer 34

affinity of the e- acceptor for the electron.

Question 35

what does the nernst equation mean

Answer 35

he tendency of a redox reaction to go under conditions where the reactants and products are not at 1 M:

Question 36

what is the nernst equation?

Answer 36