Question

The respiratory quotient of a plant organ depends upon the nature of the substrate which is
A. Oxidized
B. Reduced
C. Metabolized
D. Catabolized

Answer 1

Hint: Respiration is the process by which the respiratory substrate is broken down to release energy. There are two types of respiration, namely aerobic and anaerobic respiration, where aerobic respiration is carried out in the presence of oxygen and anaerobic respiration takes place in the absence of oxygen. The respiratory quotient is defined as the ratio of the amount of carbon dioxide released to the amount of oxygen absorbed during the process of respiration. With the help of an instrument called a respirometer, we can detect the respiratory quotients of different substrates.
Complete step-by-step answer: A respiratory quotient is a logarithmic number used to calculate basal metabolic rate by the ratio of carbon dioxide liberated to the volume of oxygen absorbed. It is a dimensionless number utilized in the calculation for BMR which is measured from the production of carbon dioxide to the absorption of oxygen. The oxygen uptake is a form of indirect calorimetry and is calculated by a respirometer instantly at the mouth or tissue.
The substrate is oxidized by aerobic respiration, resulting in the evolution of carbon dioxide. RQ can be calculated for a specific substrate such as carbohydrates, lipids, or proteins.
Therefore, the correct answer is option A- Oxidized.
Note: The RQ depends on the variety of respiratory substrates that are partaking in respiration. When sugar is used as a substrate and is fully oxidized, the RQ will be 1. In the case of fats, the RQ is less than 1, and in the case of proteins, the RQ is about 0.9. In living organisms, the RQ of respiratory substrates is usually greater than one. Pure fats and proteins are not used as respiratory substrates.