Unit 1 Bioenergetics Flashcards
entropy
(S)
randomness associated with a given system
enthalpy
(H)
measure of heat content (thermodynamic potential) of a system
free energy
the amount of thermodynamic energy in a system that can be converted into work at a given temp and pressure
high energy compounds
compounds with bonds that release greater than 7 kcal/mol of energy when broken
(∆G= -7; chemical energy of greater than 7 kcal/mol)
Oxidation-reduction reaction:
a chemical reaction involving the transfer of electrons away from one or more compounds (the oxidized compounds) to one or more other compounds (the reduced compounds)
1st law of thermodynamics
energy is neither created nor destroyed. Energy can be converted into different forms but is always conserved
2nd law of thermodynamics
entropy of the universe is constantly increasing
kinetic energy
- radiant energy
- thermal
- mechanical
- electric
radiant energy
- kinetic energy
- carried in photons from sun, the ultimate source of all forms of energy in living systems
thermal energy
- kinetic energy
- protein molecules function optimally at a particular temperature or need certain thermal energy to function
mechanical energy
- kinetic energy
- movement of cells and cell components
electrical energy movement
- kinetic energy
- movement of charged particles down gradients of electric potential
potential energy
- stored in chemical bonds
- stored in concentration gradients
- stored in electric fields from charge separation
- stored in redox pairs
-∆G
- reaction is thermodynamically favorable
- will occur spontaneously at any temp
∆G is
Gibbs free energy constant
+∆G
- rxn not favorable
- will not occur spontaneously at any temp
Gibbs free energy equations
∆G = ∆G0 + (RT * ln [PRODUCTS]/[REACTANTS])
b) ∆G0 = -RT * ln (Keq)
c) ∆G = ∆H – (T * ∆S )
∆H is
change of enthalpy (of bond energy) of a reaction
exothermic rxn
-heat released
∆H is negative (favorable)
endothermic rxn
-heat is absorbed
∆H is positive (unfavorable)
∆G < 0
spontaneous
∆G > 0
nonspontaneous
∆G = 0
equilibrium
∆S is
Sprod -Sreact
change of entropy or randomness of a rxn
-∆S
unfavorable
+∆S
favorable
∆G ° ‘ determines the
position of equilibrium in a chemical rxn
a thermodynamically favorable run may not occur because
the rxn rate is limited by high activation energy
how to calculate ∆E
subtract Eo of the electron donor from the Eo of the electron acceptor
Eo of a molecule is high when_______
and high negative when ____
the molecule is more electronegative
the molecule is more electropositive
when ∆E is positive,
∆G is negative and the rxn is more spontaneous
Coupling means
the sum of the run determines the spontaneity, thus allowing a rxn of +∆G to continue if paired with a -∆G rxn of greater absolute value
can couple a very favorable rxn with an unfavorable one to make the overall rxn favorable
High energy bonds
- thioester bonds
C–S: acetyl CoA - Hi energy phosphate bonds
hi energy phosphate bonds
- Phosphoanhydride (P–O–P bonds, ATP)
- (P–N) bonds: phosphocreatine
- (C–O–P) bonds: phosphoenolpyruvate
the source of energy in all cells
thioester bond in acetyl CoA
nucleophilic attack can occur at ______ on ATP
3 locations of ATP
but beta and delta release much more energy than the alpha
the energy yield from ATP, ∆G, depends on
concentrations of reactants and products in the cell
oxidation
loss of electrons
reductions
gain of electrons
reduction potential E is a measurement of
readiness with which an atom or molecule accepts an electron relative to H+
the more positive the E, the
more a molecule like electrons
the more negative the E value, the
more it likes to donate electrons
reduction potential is measure in
volts
the energy yield from oxidation of fuels depends on ______
the oxidation states of carbon in different compounds
in cells, _____ is the major source of electrons, _______ is the final electron acceptor
glucose
O2
the “circuit” for electron flow is a
series of proteins, including cytcochromes with co-factors such and Fe2+/Fe3+ containing heme groups that are alternatively oxidized/reduced and release energy in small steps
emf is used to
make high energy compounds ATP, NADPH, NADPH that are used to do biological work
potential energy is stored as
NADH
ATP is made by
harnessing the energy in gradients of H+ concentration and electrical potential across the inner membrane of mitochondria
high energy phosphate bonds
- ATP
- P-N Bonds (phosphocreatine)
- C-O-P bonds: (phosphoenolpyruvate)
in cells, major source of electrons
glucose
in cells, final electron acceptor
O2
compounds such as _____ give off lots of energy when they combust, they have large ____
carbohydrates
lipids
ΔG
one of the major ways to harness energy for production of ATP
oxidation of glucose
ΔG’o= -686 kcal/mol
