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Flashcards in Energetics of Key Metabolic Steps Deck (36)
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1

Free energy change equation? 

Concentrations must
be in molar units

 

RT log = 1.36 log

2

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

log more negeative, ΔG  more negative

3

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

greater tendency to proceed from left to right

4

standard free energy chain equals

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

5

what is the TOTAL standard free energy chain

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

6

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

change 

7

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

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.

8

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

ΔG°ʹ′ = -nFΔE°ʹ′

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

9

the potential
difference in an oxidation reduction reaction 

where reactants and products are not 1 M.

10

 as the concentration of substrates increase, ΔE ___ 

increases

11

The actual free energy change can be calculated from

ΔG = -nFΔE 

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

12

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

given set of conditions

13

ΔG°, the free energy change under some ___ conditions

standard

14

Why is ΔG° useful? 

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

15

To convert kcal/mol to kjoules/mol multiply by 

4.18 kJ/kcal.

16

Standard State

∆G = ∆G°, when 

 [subst] and [prod] = 1 M

17

all spontaneous reactions have a 

negative free energy change

18

biochemests standard state

if water is a product or substrate it is defined as

55.5 M = H20

19

biochemests standard state

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

20

atp hydrolysis

what is the free energy change equation? 

21

ΔG = 0, the reaction has no tendency for 

net reaction in either direction

22

A to C free energy change?

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))

23

A to C?

24

Cannot use ΔG to predict ΔG at a___

 catalytic site 

the environemnt may be different here

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 

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.

26

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

all steps have a negative ΔG.

since P/S has to be small enough

27

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

 

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

28

redox

electron transfer often occurs via the transfer of 

hydrogen atoms

29

redox half reaction

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.

30

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

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