1. What thermodynamics can tell us about Living Organisms?

2. Classical thermodynamics
Closed system
A system, over the border of which only energy can be transmitted.
Open system
A system, over the border of which both energy and mass can be transmitted.
Ecosphere is e closed system.
All living systems are open.
Classical thermodynamics
Any physical system will spontaneously approach a stable condition (equilibrium) that can be described by specifying its properties, such as pressure, temperature, or chemical composition. If the external constraints are changed, then these properties will generally alter. The science of thermodynamics attempts to describe mathematically these changes and to predict the equilibrium conditions of the system.
But living systems are open
far from equilibrium systems

3. Equilibrium Non equilibrium Arrow of TIME Being Becoming reversibility
irreversibility
one can never step in
the same river twice (Heraclitus)
No temporal direction
Arrow of TIME
"What then, is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know."
(St. Augustine)
The microscopic world is time reversible,
the macroscopic world is not

4. Entropy determines the arrow of time
Thermodynamics laws
The first law states that energy can not be destroyed nor created.
The second law (often referred to as the 'entropy' law) states that the quality of energy is degraded in each spontaneous change.

5. entropy measures the dispersal of energy: how much energy is spread out in a particular process, or how widely spread out it becomes.
W=number of substates W1 W2
W2>W1
It is not impossible for events to reverse themselves, just very, very, very improbable

6. Natural systems do not exist in equilibrium state, but they can exist in steady state
What is a steady state?
Some examples:
So…what is the difference between equilibrium and steady state?

7. Sout>Sin Irreversible thermodynamics focuses on the system
Equilibrium state:
Steady state:
Sout>Sin
A sink for entropy is very important!

8. But quality (i.e. entropy) of this energy must be different
High quality energy must come into the system and low quality energy must come out

9. Low entropy
High entropy

10. Ecosphere is a closed system in touch with a hot source (the SUN) and with a cold sink (the space)
number of subsystems extremely high
number of entropy producing processes (i.e. natural phenomena) extremely high
Hot
(5800 K)
cold
(3 K)

11. In linear conditions σ reaches a minimum at the steady state
A steady state may exist only when at least one gradient is kept constant
The gradients are referred as thermodynamic forces and they produce thermodynamic fluxes.
If non-equilibrium systems are close to the equilibrium state, the fluxes are in general linear functions of the gradients. Some examples:
Fourier’s law
Fick’s law
Ohm’s law
Poiseulle’s law
In linear conditions σ reaches a minimum at the steady state

12. In a non-equilibrium state
When the gradients are very wide, relationships between forces and fluxes are not linear anymore.
The only general rule about the solution of non-linear differential equations is that there are no general rules, but funny things can happen when linearity is lost!
macroscopic order
In a non-equilibrium state
may appear
The appearance of Bénard cells is an example of order out of chaos. The local heating causes entropy to increase, but the density inversion induces complex and non-linear behaviour.
Convection cells that arrange into a regular hexagonal lattice are an example of dissipative structures.

13. Negative entropy (negentropy)
Schrödinger introduced the concept when explaining that a living system (a dissipative structure) exports entropy in order to maintain its own entropy at a low level. By using the term negentropy, he could express this fact in a more "positive" way: a living system imports negentropy and stores it.
order
Sin
Sout
Dissipative structures are fed by a flow of negentropy wich means compatibility between the processes and the environment that is supporting the structure.
Coevolution of natural systems is at the basis of their compatibility.

14. complex molecules (low entropy matter)
What is the thermodynamic peculiarity of photosynthetic organisms?
Photosynthetic
organisms
hot photons
(low entropy energy)
CO2, H2O, simple molecules and ions (high entropy matter)
Heat
(high entropy energy)
complex molecules (low entropy matter)
Photosynthetic organisms are fed by light negentropy
becoming in turn chemical negentropy for chemotrophs

15. complex molecules (low entropy matter)
Chemotrophs are not able to use light negentropy
Heat
(high entropy energy)
Chemo
heterotrophs
complex molecules (low entropy matter)
CO2, H2O, simple molecules and ions (high entropy matter)

16. Mantaining organization requires deS<0 (Sout>Sin)
At the steady state:
Energy
and matter
Energy
and matter
Energy
and matter
Energy
and matter
Energy
Entropy
matter
matter
Produced
entropy Q
Produced
entropy
matter Q hv
matter IN
OUT IN
OUT
Photoautotroph
chemoheterotroph

17. How photosynthetic organisms are able to exploit hot photons negentropy?
Chemistry
Physics
Photosynthetic organisms are able to capture the electron from the excited state. Thanks to this, photons are converted in chemical energy.

18. Hope you are now convinced that:
2nd law is not in contrast with self-organizing living systems and ecosystems
We cannot be isolated systems
Sinks are as important as sources
Photosynthetic organisms are smart
We should love photosynthesis!