The respiratory quotient

The respiratory quotient (RQ) is the volume of carbon dioxide produced divided by the volume of oxygen consumed in the tissues in a given period of time. The value of the RQ depends on the nature of the metabolic energy source. For carbohydrates, the RQ is 1, for fats it is 0.7 and for proteins it is 0.8, A healthy subject on an ordinary mixed diet of carbohydrate, fat and protein has an RQ of typically 0.85. The RQ is of significance in its influence on the difference in pH comparing arterial and venous blood, to be described next. 

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The respiratory quotient (RQ) is often used to estimate metabolic stoichiometry. Using quasi-steady-state and by definition of RQ, develop a system of two linear equations with two unknowns by solving a matrix under the following conditions the coefficient of the matrix with yeast growth (y = 4.14), ammonia (yN = 0) and glucose (ys = 4.0), where the evolution of C02 and biosynthesis are very small (o- = 0.095). Calculate the stoichiometric coefficient for RQ =1.0 for the above biological processes ... 

For several hours after a meal, while the products of digestion are being absorbed, there is an abundant supply of metabolic fuels. Under these conditions, glucose is the major fuel for oxidation in most tissues this is observed as an increase in the respiratory quotient (the ratio of carbon dioxide produced to oxygen consumed) from about 0.8 in the starved state to near 1 (Table 27-1). 

The respiratory quotient (RQ), which is the ratio of volume of O2 absorbed per hour to volume of CO2 released per hour, should ideally be 1 when the O2 supply is not limiting. It has been reported that the CO2 to O2 ratio value is approximately 0.8 during the early period of storage and 1.3 when sprout growth started (Burton, 1989 Gottschalk and Ezhekiel, 2006 Isherwood and Burton, 1975). 

Burton, W. G. (1963). The effect of stage of maturity and storage on the respiratory quotient of potato tubers. European Potato Journal, 6, 268-270. 

Isherwood, F. A., Burton, W. G. (1975). The elTect of senescence, handling, sprouting and chemical sprout suppression upon the respiratory quotient of stored potato tubers. Potato Research., 18, 98-104. 

The respiratory quotient (RQ) (of evolution of carbon dioxide to uptake of oxygen) has been found to be near 1.0 for plant tissues and for metabolized carbohydrates. Fats evolve less carbon dioxide and have an RQ... 

Amitrole had a drastic effect on the fixation of 14C02 by illuminated chloroplasts of Chlorella pyrenaidom, lowering the incorporation into sucrose by 95% at a concentration of 500 mg. per liter it did pot affect phosphorylated compounds.145 Carbohydrates hydrolyzable by acids were higher (51%) in treated, chlorotic corn leaves than in controls (32%), and this result was interpreted as due to increased metabolism of proteins and fats. The respiratory quotient of 0.8 to 0.88, compared to controls near 1.0, supported this interpretation.145... 

Studies of the respiratory quotient or respiratory exchange ratio (RER) indicate a metabolic shift in CR rats depending on food availability, while there is little change in AL rats [21,42]. Figure 7 illustrates daily variations of RER with dietary regimen. Analysis of the food composition indicates an expected average value of RER of 0.89. RER in AL rats is 0.89 0.02 over a 24-hour period and is relatively more constant than that in CR rats, indicating that AL rats metabolize a constant ratio of carbohydrate and lipid over 24 hours [21, 42]. In contrast, CR animals metabolize more carbohydrate... 

Fig. 6.17 Relation between de novo lipogenesis, DNL, and fat oxidation, F0x, according to Eq. (38), for different values of the respiratory quotient, RQ.

Software sensors are virtual sensors which calculate the desired variable or parameter from related physical measurements [58]. In other words, there must always be a model available that relates reliably the measured variable with the target variable or parameter. Normally, measured variables are easily measurable effects that are caused and influenced by the target. The most prominent software sensor is the respiratory quotient (RQ-value) which characterizes the physiological state of a culture. However, its determination can be tricky (see Sect. 5). 

The key components for process monitoring were selected according to these data and some additional information. The in situ monitoring of the DO as well as the oxygen and carbon dioxide concentrations in the off gas allowed the evaluation of the oxygen transfer rate (OTR), the C02 production rate (CPR) and the respiratory quotient (RQ). The control of the pH-value and the DO was the prerequisite for the maintenance of the optimal growth and product formation conditions. 

The simplest parameter to express the relationships between 02 utilized and C02 produced is via the respiratory quotient (RQ). This is defined as the ratio of number of moles of C02 produced to moles 02 consumed. For the combustion of glucose,... 

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... 

One technique for assessing energy metabolism involves measurement of 05ty-gen consumption another involves measurement of arteriovenous (AV) differences. (A thiiid technique, measurement of the respiratory quotient, is discussed in detail in Chapter 5.)... 

The Respiratory Quotient during Rest and Exercise Fatty Acid Biosynthesis... 

Nutritional sciences employ various experimental techniques. The methods used to assess a deficiency can also be used to determine the requirement for a given nutrient. Dietary deficiency, a technique applied to animals and microoigan isms, was used in the discovery of vitamins and in proving the essential nature of certain amino acids and lipids. This book features a strong emphasis on the techniques used to assess both requirements and deficiencies- Two of the most important techniques, those involving nitrogen balance and the respiratory quotient, are covered in some detail. 

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