How does calorimetry relate to cellular respiration

Voit summarized early respirometric studies carried out by the Munich school on patients and healthy controls, concluding that the metabolism in the body was not proportional to the combustibility of the substances outside the body, but that protein, which burns with difficulty outside, metabolizes with the greatest ease, then carbohydrates, while fats, which readily burns outside, is the most difficultly combustible in the organism.

Extending these conclusions on the sources of metabolic heat changes, the corresponding dynamics or respiratory control was summarized Lusk : The absorption of oxygen does not cause metabolism, but rather the amount of the metabolism determines the amount of oxygen to be absorbed. MitoPedia concepts: MiP concept.

MitoPedia methods: Respirometry. Category : MitoPedia. Navigation menu Personal tools Log in. Namespaces Page Discussion. Views Read View form View source View history. News - Agenda. Use a butane lighter to ignite the nut. Record the temperature of the water when the nut is completely burned. Complete the data table by calculating the the total calories in the pecan. Error Analysis: Errors may have occurred in several ways during this experiment.

One error that may have occurred is that some of the energy may have been lost during the burning. Also some of the heat measured in the water could have been due to the butane lighter used to ignite the pecan. Conclusion: The temperature of the ml of water in the can above the burning pecan was changed by the energy given off by the pecan when it was burned.

The energy given off by the burning pecan was great enough to increase the water temperature by The mass of the unburned pecan was 1.

It takes calories to raise the temperature of 1 ml of water by 1 degree Celsius. The temperature of ml of water was recorded to have increased by Since the nut had a mass of 1. The increase of temperature in the water showed that energy had been stored in the pecan. In this experiment, the amount of calories of heat energy stored in a pecan during photosynthesis was measured by a process known as calorimetry. Thus, under aerobic conditions i. The 1. This theme can be readily applied to substrate utilization and O 2 uptake during exercise and recovery.

In addition to his Nobel-winning work disproving muscle as a heat engine it was instead a chemomechanical converter , A. Hill suggested that the volume of the O 2 debt incurred after the completion of exercise was affected by the amount of lactate produced and later removed [ 6 ]. The idea that lactate levels, in part, dictates the volume of O 2 consumed caught on quickly.

Note that O 2 volumes are being quantified with this description, not energy expenditure based on substrate oxidation. For decades, lactate was thought causal to the O 2 debt. Subsequent research however disproved the notion that lactate levels affect O 2 consumption in recovery [ 7 ]. As a result, in , exercise physiologists suggested a qualitative name change to replace the lactate-associated O 2 debt hypothesis: excess postexercise oxygen consumption or EPOC [ 8 ].

Keep in mind that while glucose metabolism contains both an anaerobic and aerobic component, lactate oxidation is all aerobic. And the concept being demonstrated is not related to the thermic effect of feeding. Yet, separating glycolytic metabolism from mitochondrial O 2 uptake introduces a methodology that recognizes a quantitative difference in glucose, fat, and lactate oxidation within cells.

By representing glycolytic ATP resynthesis as a 1. Does fuel utilization influence the O 2 debt? First mentioned in the introduction, one interpretation states that fat oxidation as compared to glucose oxidation will indeed increase the volume of O 2 consumed in recovery [ 9 ]. Why did not the previously mentioned lactate oxidation—O 2 uptake studies promote this rationale? The answer appears to depend on whether the enthalpy and entropy energy exchange components of glycolysis and mitochondrial respiration are or are not considered part of an O 2 uptake to energy expenditure estimation.

In comparison with glucose, had lactate oxidation been expressed as kJ instead of by liters of O 2 , it would indeed have some influence on the volume of the O 2 debt. The concept of entropy, a thermodynamic parameter that is not measured via calorimetry, has been the focus of developmental biology for years [ 10 ]. Yet, the nutritional sciences have given little attention to this concept.

One immediate application in the recognition of entropy is with the use of O 2 uptake measurements to quantify the energy costs of living. In this regard, glucose oxidation has an anaerobic ATP resynthesis component that fat and lactate oxidations do not—this component is not measured with direct calorimetry when pyruvate is formed.

Yet, it is there. And it needs to be accounted for if energy expenditure rather than O 2 uptake is given consideration. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.