What is ATP and why is it important?

ATP (adenosine triphosphate) is the primary energy currency of cells, consisting of adenine, ribose, and three phosphate groups. Energy is released when ATP is hydrolyzed to ADP and inorganic phosphate (ATP + H2O -> ADP + Pi + energy, approximately -30.5 kJ/mol). This energy powers cellular processes including muscle contraction, active transport, biosynthesis, and signal transduction. ATP is continuously regenerated through oxidative phosphorylation, substrate-level phosphorylation in glycolysis, and photophosphorylation in photosynthesis. A typical human turns over their body weight in ATP daily, emphasizing its central role in metabolism.