A compound found in every living cell, it is one of the essential chemicals of life. It plays a key role in most biological energy transformations. It is:

Explanation

ATP is considered the energy currency of the cell because it directly provides energy for most cellular processes. It is formed during cellular respiration and used in various biochemical reactions. While NADH and FADH₂ are crucial in energy metabolism, they primarily function as electron carriers that help produce ATP. Glucose serves as a primary energy source but must be converted into ATP to be used as energy within cells.