Figure 1. Creatine Synthesis and Transport.

Note: Creatine (methyl guanidinoacetic acid) is derived from diet and biosynthesis, mainly in the liver, pancreas, and kidney, from arginine and glycine. Creatine is transported via the bloodstream to tissues with high and/or fluctuating energy demands, such as muscle, heart, and brain, where it is actively transported against a concentration gradient into cells by CRTR. Creatine is converted to phosphocreatine (PCr), which acts as a reservoir for high-energy phosphate, and is crucial for intracellular energy metabolism.