1 What is the trend that exists between the layers of the Earth and the density of the layers?

The basic repeating unit of nucleic acids are known as nucleotides. a nucleotide consists of three distinct chemical groups.

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.