Respiratory Quotient

Introduction

The respiratory quotient or respiratory ratio are one and the same. The respiratory quotient is the measure (or result) of the ratio of the volume of Co2 (carbon dioxide) developed by the body to the volume of O2 (oxygen) consumed by the body at the time of respiration in various organisms and elements. Respiratory quotient (respiratory coefficient) is related to vital topics of various processes like aerobic respiration, anaerobic respiration etc. The respiratory quotient is included in the syllabus of XI-XII science students.

About Respiratory Quotient 

All organisms perform various kinds of life processes to sustain their life. Respiration breaks various respiratory substrates to release their energy to absorb the released energy. The respiration is halved into two types aerobic and anaerobic. Aerobic respiration is undertaken by almost all living organisms to survive; they utilize food energy obtained by consuming food. Carbon dioxide is developed in the body during the aerobic respiration process and oxygen gets consumed by organisms. The measure of this process is termed Respiratory quotient or RQ.

In simple language, the respiratory quotient can be described as the ratio of the amount of carbon dioxide produced to the amount of oxygen used by one particular organism per unit time and per unit weight during the process of respiration. The respiratory quotient is denoted as RQ in general. RQ = volume of carbon dioxide developed / volume of oxygen used per unit time and mass per unit at standard measures. The RQ is calculated by the device called a respirometer. Its result can also be described as the part of the energy produced by protein during the process. RQ varies as the respiratory substrate that’s used during the respiration process.

Respiratory Quotients Characteristics 

• The lesser the oxygen consumed by or higher the carbon dioxide produced in the molecule, the higher level of RQ in the molecule
• Generally, the Respiratory quotient of any substance or organism falls between 0.7 and 1.0
• The RQ near 0.7 indicates that carbohydrate oxidation has occurred and the Respiratory quotient near 1.0 determines the occurrence of fat oxidation. Oxidation at the ends of the Respiratory quotient range is pure of their respective occurrences (i.e. Respiratory quotient at 0.7 is pure carbohydrate oxidation and at 1.0, it is pure fat oxidation)
• The carbohydrate oxidation’s Respiratory quotient generally remains low as more oxygen is consumed during carbohydrate oxidation and vice versa in the oxidation of fatty substances
• The presence of insulin in substances results in a higher level of Respiratory quotient, as insulin increases the lipid storage of substances during respiration
• A respiratory quotient is a dimensionless number (i.e.The numbers without quantitative or scalar results are called dimensionless numbers)
• The respiratory quotient is used to measure the basal metabolic rate

Respiratory Quotient Applications

• The respiratory quotient is used to measure the function level of the liver
• It is used to measure the rate of feeding (i.e. overfeeding or underfeeding)
• It’s used to assume the growth in weight of diabetic patients who are not dependent upon insulin
• It can be used to find the nature of the chronic disease called liver cirrhosis
• It can be used to determine COPD

Respiratory Quotient of Respiratory Substrates

Every element or organism has different respiratory quotients (or coefficients), which differ from various kinds of respiratory substrates. Respiratory quotients of some general elements are described below:

Respiratory Quotient of Carbohydrates

Respiratory quotient of carbohydrates is approx. 1.0 in Aerobic respiration

 C6H12O6 + 6 O2 → 6 CO2+ 6 H2O

Respiratory quotient= 6 CO2/ 6 O2=1

Respiratory quotient of carbohydrates during anaerobic respiration

C6H12O6→ 2 Ethanol + 2CO2

Respiratory quotient = Infinity

Respiratory Quotients of Proteins

By calculating the above chemical equation of proteins, the answer will be 0.8. The respiratory quotient of the proteins always results in around 0.8 (approx.)

Respiratory Coefficients of Fats or Lipids

Respiratory quotients (coefficients) of fats and lipid substrates remain approximately 0.7

2C51H98O6 + 145O2 → 102CO2 + 98H2O RQ = 102CO2/145O2 = 0.7

Applying the Respiratory quotient formula will result in 0.7 (approx.)

Respiratory Quotient of Other Respiratory Substrates

Process Related to Respiratory Quotient

The results we learned throughout the topic are obtained by calculating the oxygen and carbon dioxide exchange measures done during the respiration process. There are two cellular respiration processes – 

1.) Aerobic cellular respiration 

2.) Anaerobic cellular restriction.

Cellular respiration

The process called cellular respiration is one of the major life processes taking place in cells of organisms, where the oxygen molecules are converted in chemical energy form and nutrients into the water, wastage and CO2. This process results in ATP proteins (adenosine triphosphate), where various organisms perform different types of cellular respiration processes to survive throughout life. There are two types of cellular processes: aerobic respiration and anaerobic respiration.

Aerobic respiration

The respiration in which oxygen is used to produce more protein tissue called ATP (adenosine triphosphate) compared to anaerobic respiration is known as aerobic respiration. The process of aerobic respiration is more efficient and stronger than anaerobic respiration. Water, energy and carbon dioxide are end products of aerobic respiration. The volume of oxygen consumed during this process is a Respiratory quotient.

Anaerobic respiration

When respiration takes place in the absence of oxygen, the organic and inorganic molecules are used to produce a couple of adenosine triphosphate during respiration, resulting in a weaker and less efficient metabolism. The end products are lactic acid, ATP and ethanol, and the respiratory quotient of anaerobic respiration remains infinite.

Conclusion

Above from here, we came through all Respiratory quotients, we learned the meaning, substrates, their characteristics, their applications, and various other properties.