What prevents complex molecules from spontaneously and rapidly degrading into atoms?

Bonding.

Explanation:

Bonding prevents complex or macro-molecules from spontaneously and rapidly degrading into atoms because force of attraction present between atoms. These bonds are very strong which is only breakable when there is high amount energy is supplied so we can conclude that bonding between atoms of complex molecules are responsible for their intact structure and prevent rapid degrading into atoms.

the cell theory states that all living things including animals, as well as plants, are made of cells.