Which of the metabolites is common to respiration mediated breakdown of fats,carbohydrates and proteins?

Proteins act as respiratory substrates only when:

Identify the respiratory substrates for respiration.

In a prolonged fast,the organic substances are used by the body in which of the following sequences?

Given below are two statements:
Statement $I$ - $A$ stepwise release of chemical bond energy facilitates the utilization of a relatively higher proportion of that energy in $ATP$ synthesis.
Statement $II$ - Due to stepwise oxidation of respiratory substrate,the same pathway may be used for synthesis of another biomolecule.
In light of above statements,select the correct answer from the options given below.

The respiratory pathway can be appropriately defined as a/an ....... pathway.