Lecture 5: Bioenergy Flashcards
Energy Charge (EC)
measure of [ATP], [ADP], [AMP] in cell
reflects amount ATP for metabolic reactions
first law of thermodynamics
nrg not created or destroyed
nrg conversion in bio systems is never 100%, its good, but some is lost as heat
Second Law of Thermodynamics
w/o nrg input, all natural process tend toward DISPERSON OF ENERGY (disorder)
measure of disorder is…
entropy (S)
bomb calorimeter
can determine nrg avliable oxidation of rreduced compound
calorie
amount of heat nrg need to raise 1 kg water 1 degree C at 1 atmospheric pressure
total nrg potential of 1 gram glucose is…
SAME REGARDLESS OF METABOLIC PATH TAKEN
15.7 kJ of nrg
true or false: total amount of nrg availalble does NOT tell you if glucose ox is favorable or unfavorable
TRUE
to know if glucose oxidation is favorable or unfavorable…
know the change in GIBBS FREE ENERGY (delta G)
When delta S is greater than zero…
randomness is increasing
to restrain disorder from increasing…
nrg needs to be provided
in order to stay alive…
one must maintain order and prevent reaching equilibrium with the environment.
inc in entropy happens when a cell dies and its contentes equilibrate with environment
Ice melting as increase in entropy
at liquid state, the H bonds in the molecules break and reform more than when frozen
Delta G greater than zero…
reaction UNFAVORABLE
ENDERGONIC (reabsorbs energy)
Delta G less than zero
reaction FAVORABLE
EXERGONIC (releases energy)
Delta G = zero
reaction at EQUILIBRIUM
concs not changing (but the concs arent equal)
Gibbs free energy
relates enthalpy, temp, and entropy to predict SPONTANETIY of a reaction
enthalpy means
bonding
is represented by H
Gibbs free energy equation
Delta G= Delta H-TDeltaS
values of delta G tell whether favorable…
in DIRECTION WRITTEN
DeltaG^0’ Conditions…
1M starting conc of all reactants and products 298K pH 7 1 atm 55M H2O
DeltaG^0’ is Standard Free Energy Change
DeltaG^0’ is determined…
experimentally. ste up with standard conditions. add an enzyme (usually)
note about enzymes…
enzymes change rate, NOT concentrations at the end
DeltaG^0’ equation
DeltaG^0’=-RKlnKeq
R is gas constant
Keq=
[product]eq/[reactant]eq
ratio of product and reactant concs when reaction has reached equilibrium
DeltaG^0’ and Keq
CONSTANTS
if you have one, you can calculate the other
Keq can tell you…
its a measure of reaction directionality, so it can tell you if reaction is favored
Keq greater than one
product formation favored
exergonic
Keq less than one
product formation UNfavored
endergonic
What can be used to describe spontaneity of a reaction
Keq and DeltaG^0’
endergonic when
Keq0
exergonic when
Keqq>1
DeltaG^0’ <0
DeltaG^0’ <0
reaction favorable in direction written
DeltaG^0’ >0
reaction is UNfavorable in direction written
change in free energy equation that takes into account standark free energy change
deltaG=DeltaG^0’ +RTlnQ
temp and concs can change now
when reaction is at eq, deltaG=0
Q
[products]actual/[reactants]actual
mass action ratio
Q
measure of actual concs of reactants and producs under actual conditions
more negative delta G means…
more favorable
Coupled reactions
share metabolic intermediates
product of one rxn may be unfavorable, but if coupled with a reaction that is favorable enough to make the total deltaG be negative, the overall reaction IS FAVORABLE (see slide 19 if needed)
ATP Hydrolysis
phosphoryl transfer
used to drive reactions that are otherwise unfavorable
nrg in 2 ATP phosphoanhydride bonds to stim catalysis and metabolix flux
ATP Hydrolysis ex: convert glutamate to glutamine
use glutamine synthase glutamate->glutamine= +14 ATP->ADP+Pi= -30 overall NEGATIVE (favorable) SEE SLIDE 22
so what exactly is ATP doing in ATP hydrolysis?
phosphoryl group is transferred on to an unstable compound
nrg is avliable from unstable compound’s hydrolysis, THATS what drives the process
KNOW that we are forming a phosphorylated intermediate and THATS what drives the reaction
Adenylate System Energy Charge of the Cell
tells how much nrg available in cell at given time #phosphate bonds available for reaction
usually between 0.7 and 0.9 because of regulation of flux through anabolic and catabolic pathways
Energy Charge Equation
([ATP] + .5[ADP])/[ATP]+[ADP]+[AMP]
