Which structure is most necessary for a mitochondrion to produce new molecules

Explanation:  

The structure most necessary for a  mitochondria to produce new cells is the nucleus.

The nucleus is a very specialized structure that occurs in most cells  including the mitochondria.

It is a membrane bound organelle that contains genetic materials which is the DNA of all eukaryotic organisms(multicellular organisms)

It plays important functions such as:

1. Primarily an information center of the cell

2.Metabolism roles

3. Growth and production of new molecules in the mitochondria(mitochondrial bio-genesis).

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.