New York, NY, October 16, 2018 --(PR.com
)-- Dr. Frank Diederichs from Oasis Publishers has done outstanding research on Heat Production in Skeletal muscles using Chemical Thermodynamic Principles.
Skeletal muscles are composed of special cells, the muscle fibers, which ‑ on the basis of a coupled reaction ‑ can generate mechanical energy that is transferred to surroundings as work. In the coupled process energy from ATP splitting is converted into mechanical energy. The structural basis for such a contraction process is derived from the highly ordered lattice structure of myofibrils of muscle fibers. These latter structural elements are composed of protein filaments that include both actin and myosin. The interaction of myosin with actin via myosin heads or cross – bridges (CBs) initiates the contraction process. Shortening of myofibrils and the whole fiber is brought about by stroking CBs. The stroke is achieved by a conformational change of CBs. The transformation of the chemical energy released during the conformational change (stroke) into mechanical energy is brought about by the binding of CBs to actin filaments, which couples the stroking to shortening through sliding actin filaments. Since the energizing of CBs for the conformational change comes from ATP splitting, the overall process of contraction can be regarded as a coupled reaction, in which the ATP splitting energy is used to drive contraction.
Through the in-depth research article named “Principles of Heat Production in Skeletal Muscle Cells,” Frank Diederichs explains the thermodynamic relations when heat is produced or exchanged in skeletal muscle fibers. These processes can be influenced by conditions of open systems and steady state.
Through thermodynamic principles and mathematical calculations, Diederichs concludes that an appreciable amount of ATP’s splitting energy is not converted into mechanical energy, but is wasted as heat into the surroundings. The heat released into surroundings, however, is not only produced through irreversible chemical reactions but also through a reversible heat exchange, which is associated with an exchange of entropy.
There are different factors or reactions that are involved with heat production in muscle fibers. These include fluxes through metabolic pathways (oxidative/anoxic glycogen (Glgen) and glucose (Glu) degradation plus fatty acid (palmitic acid (Palm)) oxidation) and PCr hydrolysis reaction. In this context, Diederichs also establishes the matching of ATP demand and ATP delivery. ATP production via CK reaction, and the extent to which it supports total ATP delivery during the short while after switching from resting to a high power output, is also shown.
The findings in this article and in particular the matching of ATP demand and delivery are based on simulations published in Diederichs’ recent research paper named “Substrate utilization in skeletal muscle under conditions of low and high power output: the thermodynamics of demand and delivery pathways.”
Diederichs establishes that the irreversibly proceeding Glu oxidation in the fiber produces entropy. At steady state, only the produced entropy appears as heat in the surroundings, after reversible transfer across the system’s boundary. Diederichs concludes that in the case of muscle cells (when compared to a heat engine), it is not the kinetic energy that is transformed, but the potential energy difference between the products and reactants which generates another form of potential energy - for instance, the energy associated with the electrochemical potential difference of calcium ions in coupled calcium transport. The coupled reactions in living organisms are similar to man-made systems in that a certain degree of dissipation of maximal work, which can be regarded as a cost, is indispensably associated with power generation.
Since ATP is a critical and vital nucleotide within various cellular processes of a living being, it is essential that the ATP formation and ATP delivery should always match in order to avoid a rapid fall in the amount of ATP available in the cells. Diederichs demonstrates that when such a steady state cycling between ATP formation and splitting is reached, all involved potential thermodynamic functions of the state, for example, Gibbs energy, enthalpy, and entropy remain unchanged, which means that no heat can be produced and/or exchanged for ATP cycling under the given conditions.
Using the thermodynamic equation for the rate of heat release in a reaction, Diederichs derives the heat production rate in muscle cells by metabolic delivery pathways such as GLY (pathway of Glgen and Glu) plus PAL (pathway of Palm) or PCr hydrolysis.
For further analysis, the rates of ATP production and heat release are graphically represented for fast fibers with high and medium mitochondrial contents. Slow fibers deliver ATP in nearly the same way as fast fibers, but at a much slower rate (1.9 compared to 11.46 mM/s). The heat release rates are also analyzed where fluxes through respective pathways (such as GLY plus PAL) and/ or reactions instead of ATP production rates are considered.
The simulation results represent the time integrals of heat production in graphical format in which Diederichs essentially concludes that the anoxic pathway of Glgen metabolism (low content of mitochondria) is associated in fast fibers with an appreciably reduced heat production, compared to the oxidative pathway.
From the results of the experiments and simulations, Diederichs concludes that with a high power output, PCr reaction provides a considerable amount of ATP, whereas the metabolism supplies only a minor part. After a short while, even when PCr is not completely diminished, GLY metabolic path delivers the ATP. This early contribution from GLY metabolic pathway results in higher heat production since these reactions are associated with more negative enthalpies than PCr hydrolysis.