When a specific biomolecule is utilised as the primary respiratory substrate, the volume of carbon dioxide evolved is slightly less than the volume of oxygen consumed, yielding a Respiratory Quotient (RQ) of approximately 0.9. Identify the most likely substrate.

Step-by-step solution

The Respiratory Quotient (RQ) is defined as the ratio of the volume of CO₂ evolved to the volume of O₂ consumed during respiration. According to NCERT, the RQ depends upon the type of respiratory substrate used during respiration. When carbohydrates are used as substrate and are completely oxidised, the RQ will be 1. When fats (like tripalmitin) are used in respiration, the RQ is less than 1 (approximately 0.7). When proteins are respiratory substrates, the ratio would be about 0.9. Therefore, an RQ of 0.9 correspo