There is a video attached for explanation on Thermodynamics

1. What is thermodynamic?
Thermodynamics is concerned with the quantitative description of changes in heat and
energy, and of chemical equilibria.
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2. What information does is provides?
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3. 1. Equilibrium positions in reactions
2. feasibility of a reaction under a given circumstances.
3. insight into the nature of forces responsible for bonding between
molecules, enzymatic catalysis, functioning of DNA and RNA

4. What it fails to say?
it fails to give information on the rate of the reactions let alone if the reactions
will occur within a given period of time.

5. Basic concepts
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6. 1. System
2. Open system
3. Closed system
4. Isolated (adiabatic) system
5. State function

7. Should living organisms be considered as open,
closed or isolated system?
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9. Laws of thermodynamics
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10. First law of thermodynamics
This states that the total energy of the universe does not change. However, the forms
of energy can change.
∆E = q - W

11. 1. Negative q value indicates that heat has been emitted from the system
2. Positive q value indicates that heat has been absorbed by the system
3. Negative W value connotes that work has been done on the system by the
surrounding
4. Positive W value connotes that work has be done by the system on the
surrounding
What dictates if ∆q and ∆W are positive or negative?

12. ➢ When the same reaction is performed at constant pressure, the reaction vessel will
do work on the surroundings. Thus ∆E=q-W
Where, W=P∆V
➢ When the initial and final temperatures are essentially equal as obtained in
biological systems ∆V= ∆nRT/P
Thus W= ∆nRT
➢ By rearranging the above equation, the amount of heat released under pressure
under constant pressure is giving by
q= ∆E+W
q=∆E+P∆V
q=∆E+ ∆nRT
Δn = change in moles of gas per mole of substance oxidized (or reacted)
R = gas constant; T = absolute temperature

13. Enthalpy
Since all biological reactions occur at constant pressure and temperature, the
state function of reactions defined to account for the heat evolved or absorbed
by a system is called enthalpy and it is given by the symbol H. The changes in
enthalpy are related to changes in free energy with the following equation:
∆H=∆E+P∆V

14. Biochemical reactions in biological systems does not produce gas since they
occur largely in excess fluid. Thus V is extremely small, the product P V is
very small too, making E and H values nearly equivalent in biological
reactions.

15. Example
The changes in internal energy ΔE for the total oxidation of glucose (C6H12O6)
and stearic acid (C18H36O2) at 310 K (37oC) are −2.9 x 103 kJmol−1 and
−11.36 x 103 kJ mol−1, respectively.
(a) Calculate ΔH for these reactions.
(b) Which substance is more likely to be useful for energy storage in the body?

16. For glucose, the reaction is
C6H12O6 + 6O2 6CO2 + 6H2O
In this case, there is no volume change i.e. 6CO2 - 6O2 = 0 (both O2 and CO2 are gases at
310K). Hence
H=E+W
H=E+PΔV
V = 0
H = E
H = -2.9 x 103 kJ/mol

17. Second law of thermodynamics
This states that the universe (all systems) tends to the greatest degree of
randomization or disorderliness.
ΔS ≥ Δq/T
= applies to reversible reactions
inequality denotes irreversible reactions

18. For reversible reaction (processes)
ΔS (system + surrounding)= 0
For real (non) reversible processes
ΔS>0
For an isothermal reversible reaction the change in entropy can be reduced to
the term:
ΔS = ΔH/T

19. Free energy
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20. To evaluate the course of a reaction and taking into accounts of first and
second laws of thermodynamics, Gibbs defined the term free energy as as
measure of how far a reaction is from equilibrium

21. To evaluate the course of a reaction and taking into accounts of first and
second laws of thermodynamics, Gibbs defined the term free energy as a
measure of how far a reaction is from equilibrium designated as G.
G represents the amount of work that can be done by a chemical reaction.

22. Second law of thermodynamics indicates that a process will occur
spontaneously if Δq < T x ΔS.
For a process occurring at constant temperature and pressure Δq = ΔH.
Thus, for a spontaneous process
ΔH – TΔS < 0
The quantity ΔH – TΔS is called ΔG and if a process occur spontaneously,
ΔG < 0
G= Gibb’s Free Energy
ΔG = ΔH – TΔS

23. Third law of thermodynamics
This law asserts that as thermodynamic temperature, T approaches O K, the
entropy S also approaches zero for perfect crystalline substances.