Glucose transport

Glucose transport is movement of glucose between compartments, commonly across a cell membrane. It depends on carrier properties, carrier abundance, substrate concentrations and any coupled driving process. In facilitated transport, a simplified saturating relation $J=J_{max}C/(K+C)$ describes initial uptake under specified conditions. At high $C$, additional substrate has little effect because carrier capacity is limiting. ^[ref]

Transport and subsequent metabolism are separate steps. Phosphorylation of intracellular glucose changes the pool available for reverse transport, so measured uptake can depend on both entry and trapping. Likewise, an insulin-induced change in surface GLUT4 can alter entry without requiring a change in the intrinsic kinetics of each carrier. A tracer accumulation experiment must specify which of these processes contributes to its readout.