Carbon dioxide, energy expenditure

Consider an amphipod with a body weight of 10 xg consuming 4.0 X 10-9 mol oxygen every hour at steady state and eliminating 3.6 X 10 9 mol carbon dioxide, 0.4 X 10-9 mol N (as ammonia), and 0.1 X 10-9 mol lactic acid. The external work power is 50 X 10-9 W. The heat loss of the animal may be calculated when the following four net reactions contribute to the energy expenditure ... 

The energy expenditure may be calculated from the energy balance. Assume that (i) carbohydrate (CH), fat (F), and protein (Pr) are the only compounds involved in the oxidation process (ii) the other compounds are stationary and (iii) the uptake and elimination of oxygen, carbon dioxide, and nitrogen is instantaneous. From the first law of thermodynamics, we have... 

An adult male has an oxygen uptake of about 21.16 mol over 24 h, and the associated elimination of carbon dioxide and nitrogen is 16.95 mol and 5.76 g, respectively. The male has performed 0.12MJ of external work over the same period and his energy expenditure at rest is = 70 W. Estimate his energy expenditure, heat loss, and net efficiency for the external work. 

Pyruvate converted to PEP without using the pyruvate kinase reaction Formally, pyruvate is first converted to oxaloacetate, which is in turn converted to PEP. In the first reaction of this process P3mivate carboxylase adds carbon dioxide to pyruvate with the expenditure of one ATP equivalent of energy. Biotin, a carboxyl-group transfer cofactor in animals, is required by this enz)one ... 

It is perhaps of interest to point out that leucine is a metabolite that, while requiring the expenditure of 2 equivalents of TPNH for its formation from 1.5 equivalents of glucose, results in the production of 3 equivalents of high-energy phosphate, 5 of DPNH, and 3 of carbon dioxide. Thus, leucine excretion might be termed a minor energy-yielding pathway. 

Considering what man can do, 100 W energy expenditure does not seem much. He is, in fact, a very efficient machine. However, since there are 3.8 X 10 of us, the world population already needs the continuous production of 3.8 X 10 W in the form of food. This energy is derived from the Sun which has been absorbed by the chlorophyll in the chloroplasts and used to synthesize carbohydrates and other foodstuffs from carbon dioxide, water and nitrogen. We eat these plants or animals that have eaten plants. 

There now are three prevailing process designs for urea manufacture, licensed by Stamicarbon, Mitsui Toatsu, and Snampro-getti. The main differences between these processes are in the methods used to handle the converter effluent, to decompose the carbamate and carbonate, to recover the urea, and to recover the unreacted ammonia and carbon dioxide for recycle, with the objective being minimum expenditure of energy and a maximum recovery of heat. In some processes, a liquid is used to recycle a solution of carbamate, carbon dioxide, ammonia, and water. In others, the amount of water recycled is minimized, and only carbon dioxide and ammonia are recycled. In the older plants, or once-through plants, the off-gases are used as feed to ammonium nitrate or ammonium sulfate plants. 

Pouteau, E., S.M. Mariot, L. J. Martin, H. J. Dumon, E J. Mabon, M.A. Krempf, R.J. Robins, D.H. Darmaun, N.A. Naulet and P.G. Nguyen, 2002. Rate of carbon dioxide production and energy expenditure in fed and food-deprived adult dogs determined by indirect calorimetry and isotopic methods. Am. J. Vet Res. 63, 111-118. 

The characterization of energy balance in cells and tissues relies upon the measurement of several variables oxygen and substrate consumption, lactate and carbon dioxide production. These measurements however give only indirectly and partly quantitative information about the energy balance in obesity. Whole body calorimetry and direct measurement of cell heat production have been introduced as a complement to the assessment of energy balance in the whole organism and energy expenditure on the cellular level. 

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