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25 Cards in this Set

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Conservation of energy (1st law)
Can change form
Chemical (food)
Kinetic (motion)
Heat
Light (photosynthesis, fireflies)
H, delta H
The amount of energy is represent by the term enthalpy (H) and usually by change in enthalpy (DH)
-H
A change that leads to a negative enthalpy is a favored reaction
spontaneous
2nd law of thermodynamics
Disorder in the universe can only increase
low entropy = high order
high entropy = low order
Disorder or randomness is represented by the term entropy (S) and usually by the change in
entropy (DS)
Energy and entropy are not directly linked
It takes energy to melt ice (increased disorder)
It takes energy to created a cell (increased order)
Gibbs Free Energy
The combined effects of enthalpy and entropy
The change in Gibbs free energy is given by:
DG = DH – TDS
Favored (spontaneous) reactions require a negative DG, which can be achieved by a negative DH or a positive DS, or both
Entropy applies to biological
molecules and cells...
A properly folded protein is in a highly ordered, low entropy state
An unfolded protein is in a disordered, high entropy state
Biological order is made possible by
the release of heat energy from cells
Energetically unfavorable reactions...
can be driven by energetically favorable reactions because the net free-energy change for the paired couple is less than zero
To overcome the activation energy barrier...
most reactions require energy input from catalysts
The Free-Energy Change for a
Reaction Determines Whether It
Can Occur...
the free energy of Y is greater than the free energy of X, deltaG < 0, reaction is spontaneous
energetically unfavorable reaction, deltaG > 0, reaction only occurs if coupled w/ an energetically favorable reaction
The Free-Energy change for a
reaction...
Determines whether it can occur
Ex. of coupled reactions
a to b = DG >0
b to c = DG <0
If the sum of the two DGs is <0 the reaction from A to C is a favored reaction.
Dissociation
AB -> A + B
dissociation rate = dissociation rate constant * concentration of AB
dissociation rate = koff * [A] * [B]
Association
A + B -> AB
association rate = association rate constant * concentration of A * concentration of B
association rate = kon * [A] * [B]
At equilibrium for Association and Dissociation.....
association rate = dissociation rate
kon [A][B] = koff [A][B]
[AB]/[A][B]= kon/koff = K = equilibrium constant
The Concentration of Reactants.....
Influences the Free-Energy Change
and a Reaction’s Direction
The Standard Free-Energy Change
Makes it Possible.....
to Compare the Energetics of Different Reactions
DG = DGo + RTln[X]/[Y]
Enzymes do not change...
the equilibrium just the rate of the reaction
Cells are in a chemical disequilbrium....
because eventually the reaction will stop occurring and the cell will die because its needs fluctuate like the reaction
Rapid Diffusion Allows....
Enzymes to Find Their Substrates
Vmax and KM Measure Enzyme Performance
the greater the rate of the rate the higher the substrate concentration
Reduced
gains electrons
Oxidized
Loses electrons
NADH, NADPH, FDH2
electrns and hydrogen donators
NADP is...
an electron carrier
Electrons can be carried by...
a variety of molecules
ATP = phosphate
Biosynthesis
atp can be used to join molecules