(N/A) Respiration is the process of breaking down $C-C$ bonds of complex organic compounds through oxidation within the cells, which leads to the release of a considerable amount of energy.
Respiratory substrates: The compounds that are oxidized during the process of respiration to yield energy are known as respiratory substrates.
Carbohydrates are the most common respiratory substrates. However, proteins, fats, and even organic acids can also be used as respiratory substrates in some plants under certain conditions.
During cellular oxidation, the energy contained in respiratory substrates is not released in a single step. Instead, it is released through a series of slow, enzyme-controlled, step-wise reactions.
This energy is trapped as chemical energy in the form of $ATP$ $(Adenosine Triphosphate)$. $ATP$ acts as the energy currency of the cell, providing energy for various metabolic processes.
Additionally, the carbon skeletons produced during respiration serve as precursors for the biosynthesis of other essential molecules within the cell.