Phosphocarnic acid, also known as creatine phosphate or phosphocreatine, is a compound found in high-energy tissues like skeletal muscles and the brain. It plays a vital role in energy metabolism by donating phosphate groups to adenosine diphosphate (ADP), forming adenosine triphosphate (ATP), the body's main energy currency. Synonyms for phosphocarnic acid encompass its alternative names, creatine phosphate and phosphocreatine, which are frequently used interchangeably. These terms represent the same molecule with the same functions, serving as a readily available source of ATP during intense physical activities or in situations where immediate energy demands arise. Phosphocarnic acid, creatine phosphate, and phosphocreatine all describe this vital compound crucial for maintaining the body's energy levels.