All systems ↗Phosphate transfer is immediate
Phosphocreatine can rapidly transfer phosphate to ADP in muscle and other high-demand cells while metabolic flux catches up.
CELLULAR ENERGY / 01
ATP is a recycled currency.
Adenosine triphosphate couples energy-releasing processes to chemical synthesis, movement, transport, electrical gradients, and heat. Cells continually consume and regenerate it; ATP is not a long-term energy store.
Glycolysis acts in cytosol
Glucose-to-pyruvate conversion directly phosphorylates ADP at two reaction steps and can change flux quickly.
Mitochondria couple gradients
Respiratory electron transfer builds proton motive force; ATP synthase couples proton return to ATP formation.
Transport has a cost
ADP, phosphate, pyruvate, fatty acids, and reducing equivalents require specific shuttles or transporters across membranes.
Motors create movement
Myosin, kinesin, dynein, and related proteins hydrolyze ATP during contraction, intracellular transport, and cell division.
Pumps maintain gradients
Na⁺/K⁺-ATPase and calcium pumps sustain membrane potential, osmotic balance, excitability, and controlled calcium signals.
Synthesis consumes ATP
Protein, nucleic-acid, glycogen, lipid, and other biosynthetic processes spend ATP directly or use related activated intermediates.
Heat is unavoidable
Energy conversion is not perfectly efficient. Heat arises from ATP use, proton leak, and other reactions and contributes to thermoregulation.