Which of the following biological molecules is common in the respiratory breakdown of fats,carbohydrates,and proteins?

Protein cannot be used directly as a respiratory substrate; it breaks down into which of the following?

Where does glycerol enter the respiratory pathway?

In an amphibolic pathway,fatty acids would be first degraded into..........

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.

What substances are transported by $Xylem$ and $Phloem$ respectively?