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In respiration of substrate of organic acids, the RQ shall be
A. Unity
B. Less than one
C. Zero
D. More than one

Last updated date: 13th Jun 2024
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Hint: The respiratory quotient is also called respiratory coefficient is a type of dimensionless number. It is used in the calculations of the basal metabolic rate of the system.

Complete answer:
Respiratory quotient is defined as the ratio of volume of carbon dioxide evolved to the volume of oxygen consumed in respiration per unit time per unit weight at standard temperature and pressure. It is represented by the formula:
RQ = Volume of carbon dioxide released/Volume of oxygen consumed (per unit time and per unit weight at standard temperature and pressure).
The instrument which helps in measurement of Respiratory Quotient is called the Respirometer.
Characteristics of Respiratory Quotient:
-The respiratory coefficients differ in organisms for metabolic balance and it ranges from $1\cdot 0$ to $0\cdot7$.
-Respiratory Quotient is measured as a contribution from the energy produced from proteins. So no single respiratory quotient can be assigned to the oxidation of protein.
-It refers to the caloric value for each litre of carbon dioxide produced.

In aerobic conditions, as the organic acids break down as respiratory substrate the RQ greater than 1 is seen for organic acids. Example for malic acid the Respiratory Quotient will be $1\cdot3$ whereas the RQ for carbohydrates is $1$, for fats/lipids it is $0\cdot7$.
Hence it is important in dealing with animal metabolism as it helps in comparing the volume of oxygen consumed by an organism which helps in gaining information about the source of energy a living organism is using.

Hence, the correct answer is option (D).

Note: Respiratory Quotient is hardly one in a living organism as it appears to be more than one. Pure proteins and fats are never used as respiratory substrates. Hence it helps to define the respiratory substrate and also helps in understanding the type of respiration that is carried out.