I prepare a concept based on entropy production and accummulation in the living systems. Unlike generally accepted ideas, the concept is not based on the presumption that living systems should be isothermal ones, i.e. they make energy by heat transfer. I know that the presumption of "isothermality" or how to call it is used in numerous concepts and theories. Still, I would be very grateful for any arguments undermining this presumption. J.
Greetings,
From thermodynamic regards, living systems generates heat from the chemical energy consumed as food through the metabolic processes. The organs in which these metabolic processes occurs work as heat sources and are typically at a higher temperature than the rest of the living body.
Nevertheless living systems tends to regulate internal temperature and to distribute thermal energy through all the body by a circulation system (blood in large living systems). Thus the assumption of isothermal bodies in living systems is largely accepted.
Few living organism would bear a sustained and large temperature difference within their body without suffering any damage.
Hello Julie!!
The answer provided by Johane is pretty much on point. Locally, there are temperature gradients present in a lot of the processes that occur in living organisms, obviously, the magnitude of such temperature gradients varies from organism to organism, but for example, in humans, significant temperature gradient can lead to serious health issues, so for most analysis the isothermal assumption will work.
Regards
Ricardo
Hello Julie.
The topic of entropy production in living organism is a little controvertial. There are numerous papers where is applied maximum entropy production principle and minimum entropy production in living organisms. Prigogine's principle of minimum entropy production is applied in near-equilibrium situations and maximum entropy production principle has not an accepted theoretical justification.
But what is true, is that temperature gradients has been measured in different type of cells, with temperature differences between 0 to 1 celsius. Concepts like thermogenesis (in muscle cells), temperature compensation (photosynthetic cells) and oscillatory processes (eg. phosphofructokinase enzyme) in metabolism could be a proof of that. For example, it has been determined that in higher plants there are temperature gradients of up to 0.8 celsius in the surface of plant leaves. It has been associated to the processes of gas exchange and leaf transpiration, which cause a latent heat flux that results in the cooling of a leaf with respect to its surroundings.
I hope it could be of help.
Kiyonaka, S., Kajimoto, T., Sakaguchi, R., Shinmi, D., Omatsu-Kanbe, M., Matsuura, H., ... & Mori, Y. (2013). Genetically encoded fluorescent thermosensors visualize subcellular thermoregulation in living cells. Nature methods, 10(12), 1232-1238.
Garbe, C., Schurr, U., & Jaehne, B. (2002, March). Thermographic measurements on plant leaves. In AeroSense 2002 (pp. 407-416). International Society for Optics and Photonics.
Sorek, M., & Levy, O. (2012). The effect of temperature compensation on the circadian rhythmicity of photosynthesis in Symbiodinium, coral-symbiotic alga. Scientific reports, 2.
Kjelstrup, S., Rubi, J. M., & Bedeaux, D. (2005). Energy dissipation in slipping biological pumps. Physical Chemistry Chemical Physics, 7(23), 4009-4018.
Hello everybody!
Thank you so much for the answers!
For the purpose of our theory we presume that living organisms ARE NOT isothermal, as we presume they react to environmental stimuli via increased entropy production associated with heat pertubances.
However, we did not found a sound justification for this non-isothermal approach, as most of the concepts simply presume that the body temperature doesn't change.
Thanks! J
Dear Julie,
A living body left alone, I mean without a self thermal regulation, would be highly non isothermal. However it would not last long in this condition as certain vital metabolic functions need a very narrow range of temperatures. So to say thermal regulation (TR) is a need, but it is possible just in a well organized systems; a volvox have no TR neither a fetus. They live in thermal regulated media, this is also the way cold blooded organisms thrive, however they have limited mobility. Then TR is an artifact invented by evolution to gain autonomy. Either the organisms live in a TR media or they are TR themselves. Now evolution managed to adapt life to a broad range of temperatures, apparently nothing would stop the existence of a non-isothermal organism. The problem is the common origin, all the cells in a highly organized living system as a mammal have a evolutionary common origin, why would they have different metabolic temperatures?
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