Bioenergetics Flashcards
Define entropy (S)
measure of the randomness or disorder of a chemical system
What does a Positive (+) ∆S indicate?
increase in entropy measured as an increase in randomness
What are the units of entropy?
Units: joules/mole x Kelvin= J/m xK = J/molxK
Give an example of entropy
Ex 1) irreversible loss of heat from tea kettle to kitchen
Ex 2) oxidation of glucose (1 glucose + 6 O2 -> 6CO2 +6H2O) 7 molecules to 12 molecules: anytime chemical rxn increases # of molecules, solid -> liquid, liquid -> gas => entropy increases
Ex 3) information as energy (words/ passages have meaning, scrambled letters do not) information is “negative entropy”
Define enthalpy (H)
reflects the heat content of a reacting system
- A measure of the total thermodynamic energy in a system including:
Number and kinds of chemical bonds in reactants and products
Thermodynamic potential
Volume & pressure
What is the ∆H of a system?
∆H system = ∑ of non-mechanical work done on it & heat supplied to it
What does (+)∆H indicate?
(+)∆H = endothermic reaction (take up heat)
What does ( -) ∆H indicate?
( -) ∆H = exothermic reaction (release heat)
What are the units of entropy (H)
Units: joules/ mole = J/m or calories/ mole (1 cal = 4.184J)
What is free energy? (G)
the maximum amount of non-expansion work that can be extracted from a closed system
∆G = chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature => appropriate measure of spontaneity of process occurring at constant pressure and temperature
What are the units of G?
Units: joules/ mole = J/m or calories/mole (1 cal = 4.184J)
What does Negative ( - ) ∆G indicate?
Negative ( - ) ∆G = spontaneous
What does Positive ( + ) ∆G indicate?
Positive ( + ) ∆G = non-spontaneous
What is an endergonic reaction?
Endergonic reaction is energy requiring
What is an exergonic reaction?
Exergonic reaction is energy releasing
How do cells complete energetically unfavorable reactions?
Cells rely on molecules (proteins/ nucleic acids) with +∆G -> to complete the thermodynamically unfavorable reactions (endergonic), cells couple them with favorable (exergonic) reactions (often E released by hydrolysis of phosphoanhydride bonds of ATP)
What does the reduction potential (E) measure ?
readiness of molecule/ atom to accept e- compared to H+
more +E = more likes to accept e-
more –E = more likes to donate e-
How are metabolic fuels (carbohydrates/ fats) used to complete cellular work?
they are oxidized
How does O2’s high affinity for e- drive ATP synthesis?
O2’s high e- affinity mean e- transfer process is exergonic, energy is released to drive ATP synthesis (the goal of catabolism)
Describe the forms of kinetic energy
Radiant energy: photons from sun (ultimate source of all E in living systems)
Thermal energy: (temperature) protein molecules function optimally at a particular temperature or need certain thermal E to function
Mechanical energy: movement of cells and cell components
Electrical energy: movement of charged particles down gradients of electric potential
Describe the forms of potential energy
Stored in chemical bonds
Stored in concentration gradients
Stored in electric fields from charge separation
Stored in redox pairs
What is the equation for Keq?
keq = ([products]^#molecules of product)/ ([reactants]^# molecules of reactants)
If Keq is >1.0, what is ∆G and how does the reaction proceed?
∆G is negative
rxn proceeds forward
If Keq is <1.0, what is ∆G and how does the reaction proceed?
∆G is positive
rxn proceeds in reverse
If Keq =1.0, what is ∆G and how does the reaction proceed?
∆G is zero
rxn is at equilibrium
What is the equation for the change in Gibbs free energy for a reaction (∆G)?
ΔG = ΔH - T ΔS
How does ∆G relate to Keq?
ΔG =G0 + RT ln [PRODUCTS]/[REACTANTS]
Keq = [products]/[reactants]
ΔG0 = - RT lnK
What is the conversion between ∆G and ΔE?
ΔG = -nFΔE n = # of e- transferred F = faraday constant (96,500 joules/voltmol) – magnitude of electric charge per mole of e- ∆E = difference in reduction potential in volts, e- acceptor- e-donor
Are ∆G’s for a series of reactions additive or independent?
Standard free energy changes for a set of reactions are additive.
Free energy changes for multiple reactions can be coupled to overcome activation energy required to begin reaction
In this way a reaction with a net increase of S, but high activation E can proceed
