Valence shell
The number of electrons in the outermost shell of a particular atom determines its reactivity, or tendency to form chemical bonds with other atoms. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.
Explanation:
With continual improvements made to microscopes over time, magnification technology advanced enough to discover cells in the 17th century. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, known as cell biology.
primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide.
ATP or Adenosine triphosphate is well know for it's energy source but despite it has many roles in cell. ATP is primarily used as energy source as it has higher energy in it's phospho-di-ester bonds between P and P atoms. It is hydrolyzed to ADP & AMP to give energy.