What do humans need to do in order to synthesize most of the biochemical needed in the body?

I believe it's Amino acid!

The human body uses three types of molecules to yield the necessary energy to drive ATP synthesis: fats, proteins, and carbohydrates. Mitochondria are the main site for ATP synthesis in mammals, although some ATP is also synthesized in the cytoplasm.

as in mitosis, dna replication occurs during interphase.   in meiosis, it occurs specifically in s phase of interphase 1.