The respiratory quotient (RQ) is the amount of carbon that is emitted for every unit of oxygen ingested. It’s an indirect, yet quick, method of determining whether the growth medium is lacking in the substrate. The feeding pump is turned on/off based on the concentration of dissolved oxygen in the fermentation medium, and the DO-stat works on the principle of the respiratory quotient. The OUR or CER analysis can also be utilised as a control parameter for by-product accumulation. During fed-batch cultivation, the RQ control algorithm for oxygen delivery can be an effective strategy for generating a high concentration of a diol (acetoin + 2,3-butanediol). For the fed-batch synthesis of 2,3-butanediol, a control approach combining the RQ control and a constant residual sucrose concentration was adopted.
RESPIRATORY QUOTIENT FOR FATS
The Respiratory Quotient (R. Q) is the ratio of carbon dioxide released to oxygen consumed in respiration during a particular period at a constant temperature and pressure.
When fats are used as respiratory substrates, they are hydrolysed into fatty acids and glycerol during seed germination. The RQ of glycerol after complete oxidation is 0.86. Because fatty acids have a lower oxygen content than CO2, they require more O2 for full oxidation. As a result, O2 absorption is greater than CO2 liberation, and RQ falls below unity.
It is measured by using a respirometer. Because various energy pathways are used for lipids, carbs, and proteins, the respiratory quotient value reveals which macronutrients are being digested. The RQ for lipid metabolism is roughly 0.7, for proteins, it is approximately 0.8, and for carbs, it is approximately 1.0. However, the majority of the time, energy consumption is made up of both fats and carbohydrates. Energy balance, circulating insulin, and insulin sensitivity are some of the additional factors that may influence the respiratory quotient.
It can be used in the equation for alveolar gas.
Respiratory Quotient Characteristics
The caloric value of each litre (L) of carbon dioxide produced is referred to as the respiratory quotient. When data on oxygen consumption is available, it is typically used directly because it is a more direct and dependable measure of energy output.
The energy produced by protein is used to calculate the Respiratory Quotient. However, no one Respiratory Quotient can be allocated to the oxidation of protein in the diet due to the intricacy of the different methods by which distinct amino acids might be oxidised.
In general, more oxidised compounds, such as glucose, require significantly less oxygen to properly metabolise and so have higher respiratory quotients. Less oxidised molecules, such as fatty acids, on the other hand, require more oxygen for their entire metabolism and so have lower respiratory quotients.
Calculation of RQ in fats
The respiratory quotient (RQ) is defined as the following ratio:
CO2 released /O2 consumed =RQ
CO2 and O2 must be given in the same units and in quantities proportional to the number of molecules in this computation. Moles or quantities of gas at standard temperature and pressure would be acceptable inputs.
Compounds comprising simply the elements carbon, hydrogen, and oxygen make up a large portion of metabolic substances. Fatty acids, glycerol, carbohydrates, deamination products, and ethanol are all examples.
The RQ for fats is determined by the specific fatty acids present. RQ ranges from 0.692 (stearic acid) to 0.759 (oleic acid) among the typically stored fatty acids in vertebrates (docosahexaenoic acid). Historically, it was considered that ‘typical fat’ had an RQ of 0.71, and this is still the case for most mammals, including humans. However, aquatic species, particularly fish, have fat that should give greater RQs on oxidation, reaching as high as 0.73 due to high levels of docosahexaenoic acid, according to a recent study.
CONCLUSION
Subjects with a respiratory quotient in the lower range (0.72) on day 28 were better able to maintain the weight reduction obtained with the very low-calorie diet over the follow-up period, whereas those in the higher range (> 0.75) were less able to do so. The Respiratory Quotient (R. Q) is the ratio of carbon dioxide exhaled to oxygen consumed in respiration over a set period of time at a set temperature and pressure. In this calculation, CO2 and O2 must be expressed in the same units and in quantities proportionate to the number of molecules. CO2 and O2 must be expressed in the same units and in proportion to the quantity of molecules involved in this calculation. Acceptable inputs would be moles or amounts of gas at standard temperature and pressure.