Question

Considering the following chemical equation, guess what could be the nature of respiratory substrate?  

$2\,\mathrm{C}_{51}\mathrm{H}_{98}\mathrm{O}_{6} + 145\,\mathrm{O}_{2} \rightarrow 102\,\mathrm{CO}_{2} + 98\,\mathrm{H}_{2}\mathrm{O} + \text{Energy}$

• A. Carbohydrate as well as protein
• B. Fat
• C. Protein
• D. Carbohydrate

Hint:

High hydrogen and low oxygen content in a molecule indicates fat as a respiratory substrate.

Answer 1

The Correct Option is B

Step 1: Observing the chemical formula.
The given substrate has a very high proportion of carbon and hydrogen compared to oxygen, as seen in the formula C\textsubscript{51}H\textsubscript{98}O\textsubscript{6}. Such a composition is characteristic of lipids.
Step 2: Comparing respiratory substrates.
Carbohydrates have a C:H:O ratio of approximately 1:2:1, while fats have much less oxygen and more hydrogen. Proteins also contain nitrogen, which is absent here.
Step 3: Energy yield and oxygen requirement.
Fats require more oxygen for oxidation and produce more energy, CO\textsubscript{2}, and H\textsubscript{2}O compared to carbohydrates. The equation shows a large oxygen requirement, supporting fat oxidation.
Step 4: Conclusion.
The respiratory substrate represented in the equation is fat.