Question

The respiratory quotient of glucose is :
(A). $0.5$
(B). $0.7$
(C). $1.0$
(D). $1.5$

Answer 1

The respiratory quotient measures the ratio of the volume of carbon dioxide $\left( {{V_c}} \right)$ produced by an organism to the volume of oxygen consumed $\left( {{V_o}} \right)$. By determining the volume of the respiratory quotient, the nature of respiratory substrate can be known.

Complete answer:
Respiratory is the process by which the respiratory substrate is broken down to release energy. The most common respiratory substrate is glucose, which has a 6- carbon compound. The substrate is metalized through glycolysis, TCA cycle, electron transport chain, and oxidative phosphorylation.
Respiratory quotient $\left( {RQ} \right)$, also known as the respiratory ratio, is defined as the volume of carbon dioxide released is the volume of oxygen absorbed during respiration . It is used in calculation for basal metabolic rate when estimated from $C{O_2}$ production to oxygen absorption.

Formula used:-
$RQ = \dfrac{{\operatorname{Volume} of{\text{ C}}{{\text{O}}_2}{\text{ }}\operatorname{released} }}{{\operatorname{Volume} of{\text{ }}{{\text{O}}_2}{\text{ }}\operatorname{absorbed} }}$.
In this calculation, the $C{O_2}$ & ${O_2}$ must be given in the same units, and in quantities proportional to the molecules.
For glucose, respiratory quotient will be calculated as:-
Glucose has the molecular formula, ${C_6}{H_{12}}{O_6}$, the complete oxidation equation is :-
${C_6}{H_{12}}{O_6} + 6{O_2} \to 6CO2 + 6{H_2}O$ .
Substituting the value in $RQ$, formula.
$RQ = \dfrac{{6C{O_2}}}{{6{O_2}}}$

Therefore, $RQ$ of glucose is 1.

Note: $RQ$ value corresponds to a caloric value for each liter of $C{O_2}$ produced. If ${O_2}$ consumption numbers are available, they are generally used directly, since they are more direct and reliable estimates of energy production.