Which molecule provides the primary energy source for cellular processes?

The primary energy source for cellular processes is ATP, or adenosine triphosphate. ATP functions as the main energy currency of the cell, providing the energy necessary for various biochemical reactions, including muscle contraction, protein synthesis, and active transport across cell membranes.

ATP is synthesized during cellular respiration through processes such as glycolysis and the citric acid cycle, where energy from nutrients is converted into a usable form. It consists of adenosine and three phosphate groups, and when one of these phosphate bonds is hydrolyzed, energy is released, which can then be harnessed by the cell for various functions.

While glucose is an important energy source for the cell and serves as a substrate for ATP production, it needs to be metabolized first to produce ATP, thus it is not directly used for energy. NADH and FADH2 are electron carriers involved in cellular respiration, aiding in the production of ATP through the electron transport chain. However, they themselves do not directly provide energy for cellular processes.