Thermodynamics Flashcards
Bioenergetics:
quantitative analysis of how organisms gain and use E
Systems are…
what we are studying
- has to have defined boundaries
Types of systems:
- open
- isolated
- closed
Open system is…
able to exchange both E and matter
Isolated system is…
unable to exchange E and matter with surrounding
Closed system is…
able to exchange E but not matter
Internal E consists of…
- kinetic E of motion
- E of rotation
- E of vibration
- E stored in chemical bonds
- E of non-covalent interactions between molecules
T/F: internal E is a function of state of a system
T
States of system are defined by..
- temp
- pressure
- volume
State functions does not depend on…
the pathway the system took
- only depends on current state of system
Examples of state functions:
- internal E
- enthalpy
- entropy
- Gibbs free E
Process functions depend on…
pathway between 2 equilibrium states
Examples of process functions:
- temp
- heat
- work
Work can’t be a state function b/c…
it’s proportional to distance object is moved
Changes in internal E of the system and its surroundings is accomplished by…
- heat transfer to and from system
- work on its surrounding from surroundings
Examples of work forms:
- expansion of system against pressure
- expansion against surface tension
- contraction of muscle
Heat (q):
(+) q = heat absorbed by system
(-) q = heat given off to surroundings
Work (w):
(+) w = work done by system
(-) w = work done on system by surroundings
First law of thermodynamics:
E can’t be created or destroyed
delta E = q - w (path independent)
Ideal gas law:
PV=nRT
Enthalpy (H) is a ______ function
state
What contributes to enthalpy?
- work
- heat
T/F: delta H = delta E
T b/c volume changes are small in biochem
Formula for H at constant pressure:
delta H = delta E + P(delta V)
Second law of thermodynamics:
entropy of isolated system will tend to increase to max value
Entropy (S) is the relative degree of…
disorder measured by a state function
Formula for entropy:
S = klnW (k=boltzmann constant)
Positive entropy contributions are increased…
- motions
- rotations
- degrees of freedom
- particle #
- disorder based on state of matter
- number of molecules
- spatial distribution of molecules/particles
An open system needs a function of both…
- entropy
- enthalpy
Gibbs free E (G):
state function that combines both entropy and enthalpy
Gibbs free E formula:
delta G = delta H - T(delta S)
Exergonic:
thermodynamically favorable (-delta G)
Endergonic:
thermodynamically unfavorable (+delta G)
If delta G = 0, then system is…
in equilibrium
At low T, delta H dominates and delta G is…
positive
At high T, T(delta S) dominates and delta G is…
negative
(-) delta H and (+) delta S =
spontaneous (-delta G)
(-) delta H and (-) delta S =
spontaneous only at low temp
(+) delta H and (+) delta S =
spontaneous only at high temp
(+) delta H and (-) delta S =
unspontaneous
How to calculate free E:
delta G = G(prod) - G(reactants)
Standard free E change:
- delta G = RTlnK
K = e^(- delta G/RT)
T/F: unfavorable reactions will never be favorable
F, can be made thermodynamically favorable by coupling them to favored reactions
High E compounds are compounds w/…
large negative free E changes
Examples of high E compounds:
- phosphate anhydrides
- enol phosphates
- thioesters
- compounds containing N-P bonds
Hydrolysis of ATP is…
highly exergonic
- delta standard free E = -31 kj/mol
Why is hydrolytic release of phosphate high in E?
- resonance stabilization of phosphate products
- electrostatic repulsion between charged products
- tautomerization
- release of proton in buffered solution (pH influences equilibrium)
