Entropy Generation and Human Aging: Lifespan Entropy and Effect of Physical Activity Level

Abstract

Abstract:The first and second laws of thermodynamics were applied to biochemical reactions typical of human metabolism. An open-system model was used for a human body. Energy conservation, availability and entropy balances were performed to obtain the entropy generated for the main food components. Quantitative results for entropy generation were obtained as a function of age using the databases from the U.S. Food and Nutrition Board (FNB) and Centers for Disease Control and Prevention (CDC), which provide energy requirements and food intake composition as a function of age, weight and stature. Numerical integration was performed through human lifespan for different levels of physical activity. Results were presented and analyzed. Entropy generated over the lifespan of average individuals (natural death) was found to be 11,404 kJ/ºK per kg of body mass with a rate of generation three times higher on infants than on the elderly. The entropy generated predicts a life span of 73.78 and 81.61 years for the average U.S. male and female individuals respectively, which are values that closely match the average lifespan from statistics (74.63 and 80.36 years). From the analysis of the effect of different activity levels, it is shown that entropy generated increases with physical activity, suggesting that exercise should be kept to a "healthy minimum" if entropy generation is to be minimized.

First and second law work production efficiency of a muscle cell

“…Exergy analysis of biological processes is a relatively new subject. There are limited applications for cellular processes (Silva and Annamalai, 2008;Ketzer and de Meis, 2008;Lems et al 2009;The and Lutz, 2011;Mady et al 2012;Mady and de Olivera Jr., 2013;Genç et al, 2013a;Sorgüven and Özilgen, 2013).…”

Biological Aging and Life Span Based on Entropy Stress via Organ and Mitochondrial Metabolic Loading

“…By setting · I = 0 in above equation one can show that total optimum work rate is equal to sum of optimum work of each macro-nutrient · W ATP,opt = ∑ n · m n,reacted |∆G c,n |, whole body, n = CH, F and P where · m n,reacted , the consumption rate of nutrients which could be less than · m n,i and unreacted Gibbs function of nutrients at inlet and exit cancel out. Silva and Annamalai [8] found that the availability efficiency (η Avail = work delivered/optimum work) used in thermodynamics for an isothermal system is same as metabolic efficiency in biology. Thus, metabolic efficiency (η Met )…”

“…Since the engineering studies for several fuels revealed that the ratio of change in Gibbs function to heating values of fuels/nutrients, | ∆G • c, n |/HV n ≈ C g , a constant ≈ 0.95 − 1.05 [8,16] for most nutrients. Hence |∆G c,n | * 1 − η Met,n ≈ C g HV n 1 − η Met,n where HV n is the heating value of nutrient n. Thus, after dividing by m B , Equation (6) becomes…”

“…Living systems are characteristics of systems being far from equilibrium and hence must generate entropy since birth/conception. Thus Silva and Annamalai [8,9] adopted the availability concepts from thermodynamics, showing that availability/exergetic efficiency in thermodynamics is almost same as metabolic efficiency (η M ), proposed the second law hypothesis on biological aging with a fixed amount of life span entropy generation/irreversibility, σ M,life (10,000 kJ/(K kg body mass)) for the whole body. Such a hypothesis is also consistent with Andresan's concept on constant total lifetime entropy production per unit body mass for all BS [10] except that Silva's hypothesis includes the effect of metabolic efficiency.…”

“…), and bridging of gap between data on body mass independent SMR k data of Elia [8] (but still depends on type of organ or its enzyme) with those of body mass-dependent SMR k data of Wang [13] and Singer's data [10] in biology. The SMR k will be a function of size of organ or mass of organ k when one of the following conditions are satisfied:…”