Biological cells which form bonds with a substrate and are at the same time subject to a flow can form long thin membrane cylinders called tethers, which connect the adherent area to the main body of the cell. Under physiological conditions, neutrophil tethers can extend to several micrometers. Another tether is biotin- lysine residue complex associated with pyruvate carboxylase, an enzyme which plays an important role in gluconeogenesis. It is involved in the production of oxaloacetate from pyruvate.