Bioenergetics Flashcards
entropy
(S)
The measure of microscopic disorder of a system.
enthalphy
(H)
the total energy of a thermodynamic system; ΔH is the heat generated at constant pressure
free energy
(G)
energy of a reaction that can be used to do work (negative ΔG) or the energy required to drive a reaction (positive ΔG)
high energy compounds
compounds with large negative free energies of hydrolysis (compounds that release a large amount of energy upon hydrolysis)
first law of thermodynamics
energy can neither be created nor destroyed, E of the universe is constant
second law of thermodynamics
spontaneous reactions occur in directions that will increase the overall disorder of the universe. So, the entropy of the universe is always INCREASING (ΔS>0)
What are the two main categories of energy?
kinetic energy and potential energy
What is kinetic energy?
energy in motion
What is potential energy?
stored energy
Examples of potential energy
chemical bonds
concentration gradients
electric gradients
redox pairs
What has greater reduction potential and thus more energy, lipids or carbs?
Lipids (6 bonding e to C)
[Carbs: 4 bonding e to C]
Equation for calculating the free energy at NON-STANDARD conditions
ΔG=ΔG° + RTln[products/reactants]
R=1.987cal/mol K
T=temp in K
ΔG° = free energy in standard state (298 K, 7pH, 1 atm, 1M reactants in H2O)
Equation for free energy at EQUILIBRIUM
ΔG°= -RTlnKeq=2.3RTlogKeq
When ΔG = 0 (free energy at equilibrium
When Keq is <1, ΔG° is _____
positive
When Keq is >1, ΔG° is _____
negative
When Keq = 1, ΔG° is _____
zero
Calculate Keq (at equilibrium)
Keq=kf/kr= [C][D]/[A][B] (when A+B–>C+D)
Calculate ΔG (equation)
ΔG= ΔH-TΔS
H: change in enthalpy
S: change in entropy
T: temp
For ΔG, what is spontaneous, what is nonspontaneous?
ΔG is negative for spontaneous reactions
ΔG is positive for nonspontaneous reactions
{spont doesn’t tell you rate!}
Equation for conversion b/t free energy and redox potential.
ΔG=-nFΔE *remember negative sign F=96,500 joules/volt mol n= number of electrons transferred ΔE=reduction potential in volts STANDARD CONDITIONS
What is ΔE? more positive? more negative?
Measure of atom/molec’s readiness to accept electrons.
more positive? more likely to accept electrons (high reduction potential, OXIDIZING agent)
more negative? less likely to accept electrons; low reduction potential (REDUCING agent)
Electrons flow from ____ to _____ reduction potentials.
Low to high reduction potentials.
[Move from compounds with low E, to high E (oxidized reactants), and RELEASE energy]
E=reduction potential in volts
Standard free energy changes for a reaction are______, so reactions with _____ and _____ free energy changes can be coupled.
additive
positive and negative
[Nonspontaneous reactions may be coupled with highly spont. rxn with a common intermediate to drive the nonspont. reaction FORWARD.]
Ex. of coupling reaction
ATP is often coupled with unfavorable rxns.
High energy compounds
Compounds whose bonds are hydrolyzed w/ the release of large amounts of energy (ΔG<t mean high bond energy, just means there are large differences in STABILITY of the products and reactants of hydrolysis of high energy compounds)
Examples of high energy bonds:
phophoanhydride bonds in ATP (beta and gamma are higher energy than alpha) Thioester bond (C-S-CO-C in acetyl CoA compound) Phophoenolpyruvate bond (C-O-P) Phosphocreatine bond (P-N)
Way to harvest energy for ATP production?
oxidation of glucose
