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Protein Oxidation and the Respiratory Quotient

The influence of protein oxidation on the RQ is generally ignored in clinical and experimental studies involving respiratory measurements. Hence, the RQ determined in these studies is sometimes called the tionproteirt RQ. The contributions of CO produced and O consumed by protein oxidation are small compared with those made by fat and carbohydrate oxidation. The hydrolysis of proteins to amino acids docs not contribute to the RQ, The RQ associated with the oxidation of mixtures of different amino acids is 0,80. The oxidation of protein (70 g) produces Z.4 moles of CO and consumes 3.0 moles of O (King el a ., 1984). The RQ associated with the oxidation of leucine, for example, can be calculated as follows. [Pg.295]

The caJculation assumes that all of the nitrogen released is excreted as urea, Urea, as mentioned in Chapter S, is the excretory form of most of the nitrogen resulting from protein and amino add catabolism. [Pg.296]

The total volumes of O2 consumed and COj produced with the oxidation of 1 g of glucose, fat, and protein are listed in Table 5,4- With protein catabolism, 1 g of urinary nitrogen is associated with the consumption of 6-04 liters of O2 nd the production of 4-S9 liters of COj. [Pg.296]

Respiratory measurements alone can be used to determine the amounts of carbohydrate and fat oxidized in the body over a given period. These amounts can be more accurately determirted by including data from urinary nitrogen measurements in the calculations. According to Frajm (19S3), the grams of carbohydrate (c) and fat y) oxidized per minute can be calculated from the formulas [Pg.296]

TABLE 5.4 Total Volumes of O3 Consumed and Produced upon Oxidation of Olucose, Fat, and Protein [Pg.296]


Respiratory Quotient Data from Human Studies Protein Oxidation and the Respiratory Quotient Calculating Energy Expenditures... [Pg.1011]

Indirect calorimetry, a technique that measures Oj consumption and COj production, can be used when more accurate determinations are required for hospitalized patients. A portable indirect calorimeter is used to measure oxygen consumption and the respiratory quotient (RQ), which is the ratio of Oj consumed to COj produced. The RQ is 1.00 for individuals oxidizing carbohydrates, 0.83 for protein, and 0.71 for fat. From these values, the daily energy expenditure (DEE) can be determined. [Pg.8]

Insulin is probably the most important inhibitor of lipolysis. In contrast to adults, in whom catecholamines represent the most important stimulators of lipolysis, thyrotropin (TSH) is the most important stimulator of lipolysis in the newborn. Plasma free fatty acid concentrations rise markedly in the first hours after birth in response to a marked increase in the TSH concentration and a fall in the insulin concentration. The fatty acids released from lipid stores are oxidized by some extrahepatic tissues (e.g., heart and skeletal muscle, kidney, intestine, and lung). Because the respiratory quotient (the ratio of carbon dioxide production to oxygen use) falls from a value of 1.0 (showing that carbohydrate oxidation is the primary source of energy) to a value of 0.8 to 0.9 (showing increasing oxidation of protein or fatty acids) at 2 to 12 hours of age, at a time when protein catabolism is usually insignificant, fatty acid oxidation must represent... [Pg.113]

Animals do not normally obtain energy exclusively from either carbohydrate or fat. They oxidise a mixture of these (and protein). Consequently, in order to apply the appropriate thermal equivalent, it is necessary to know how much of the oxygen is used for oxidation of each nutrient. The proportions are calculated from what is known as the respiratory quotient (RQ).This is the ratio between the volume of carbon... [Pg.264]

The metabolism of proteins gives a ratio of carbon dioxide produced to oxygen consumed that is intermediate between that of carbohydrate and fat - this is because proteins contain relatively more oxygen per carbon than do fats, although less than carbohydrates. For protein metabolism the respiratory quotient = 0.8. The amount of protein being oxidized can be determined quite separately, by measurement of the excretion of urea, the end-product of amino acid metabolism (section 9.3.1.4). [Pg.119]

Here G denominates the glucose oxidation rate, F the fat (Palmitoyl-stearoyl-oleoyl-glycerol) oxidation rate, P the protein oxidation rate and RQ the respiratory quotient, which is the quotient of carbon dioxide production and oxygen consumption RQ = CQ/Oj- The RQ is not only a theoretical quotient characterising each of the metabolites, but a very important factor in whole body calorimetry, characterising the actual ratio of the oxidised substrates. [Pg.521]

There are no convincing experimental data, based on respiratory quotients, which support the hypothesis that fatty acids are convertible to sugar. Contrasted with the marked alterations which have been observed when carbohydrate is being changed to fat, the decreases in R. Q. below the level of 0.707 for fat, which should be observed if fat were changing to carbohydrate, are very small and can be partially if not entirely explained by alterations in the R. Q. of the metabolized protein and fat, due to their incomplete, oxidation. [Pg.156]

In some situations, discussed in more detail later, heat production has to be estimated from oxygen consumption alone. If a respiratory quotient of 0.82 and a thermal equivalent of 20.0 kJ/1 are assumed, then departures from this RQ in the range of 0.7-1.0 cause a maximum bias of no more than 3.5 per cent in the estimate of heat production. A further simplification is possible in respect of protein metabolism. The thermal equivalent of oxygen used for protein oxidation is 18.8 kJ/1, not very different from the value of 20.0 assumed for carbohydrate and fat oxidation. [Pg.265]


See other pages where Protein Oxidation and the Respiratory Quotient is mentioned: [Pg.273]    [Pg.295]    [Pg.273]    [Pg.295]    [Pg.295]    [Pg.273]    [Pg.295]    [Pg.273]    [Pg.295]    [Pg.295]    [Pg.167]    [Pg.62]    [Pg.544]    [Pg.886]    [Pg.77]    [Pg.256]    [Pg.489]    [Pg.346]    [Pg.544]    [Pg.92]    [Pg.1406]    [Pg.375]   


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