Which molecule is the primary energy source for biological work?

ATP, or adenosine triphosphate, is considered the primary energy currency of the cell. It plays a central role in numerous biological processes, serving as the main molecule through which energy is transferred within cells. When ATP is hydrolyzed, it releases energy that can be harnessed for various cellular functions, such as muscle contraction, active transport across membranes, and synthesis of macromolecules.

While NADH and glucose are important in energy metabolism, they serve different roles in the process. NADH is primarily involved in electron transport and is a carrier of high-energy electrons during cellular respiration. Glucose is a key fuel source for generating ATP, but it must first be metabolized through pathways like glycolysis and the citric acid cycle to produce ATP. Creatine, on the other hand, serves as a quick energy buffer in muscle cells by enabling the rapid regeneration of ATP from ADP during short bursts of high-intensity exercise.

In summary, ATP is the molecule that directly fuels most biological work, making it the primary source of energy in biological systems.