Biochem flashcards

Thermodynamics

the study of energy. It can provide information about how and why a

reaction can occur. It can also provide information about the conditions

required for a reaction to occur.

First Law of Thermodynamics

Energy is conserved. It cannot be created or destroyed but only converted

from one form to another.

Forms of energy

• Kinetic

• Potential

• Heat

• Chemical

Second Law of Thermodynamics

The total entropy the universe increases for any process

that is spontaneous.

Third Law of Thermodynamics

The entropy of a perfect crystalline system at 0 K is 0.

Entropy

a measure of the unavailable energy in a closed thermodynamic system that is also usually considered to be a measure of the system's disorder, that is a property of the system's state, and that varies directly with any reversible change in heat in the system and inversely with the temperature of the system

Enthalpy

the total heat content of a system, representing the system's internal energy plus the energy needed to make room for it by pushing against its surroundings.

Spontaneity

Spontaneous processes proceed without continuous input of energy under given conditions, while nonspontaneous processes require ongoing external energy. If a process is spontaneous in one direction under certain conditions, the reverse process is nonspontaneous under those same conditions.

Gibbs Free Energy

Formula helps determine spontaneity.

ΔG = ΔH − TΔS

H = enthalpy – heat flow (usable work)

T = temperature (in K)

S = entropy – accessible states (unusable work)

Another equation for it is: ΔG = ΔG° + RT ln Q

ΔH

(-) means always spontaneous or spontaneous at low temps

(+) means spontaneous at high temps or never

ΔS

(-) means spontaneous at low temps or never

(+) means spontaneous at high temps or always

ΔG

(-) means always spontaneous

(+) means never spontaneous

Spontaneous at high or low temps could be either

ΔG°

Standard Free Energy State ΔG° = -RT ln Keq

Free energy at standard state conditions:

• T = 298K

• P = 1 atm

• [solutes] = 1 M

Tells whether is reactant-favored or product-favored.

ΔG° = + reaction is reactant-favored

ΔG° = - reaction is product-favored

Q

Reaction Quotient Q = [ADP3-][HPO42-][H+]/[ATP4-]

The Reaction Quotient tells which way the reaction is proceeding.

Q < Keq, reaction is proceeding to right

Q > Keq, reaction is proceeding to left