Figure 3.

Free energy transduction and biomolecular cycles: model. (a) As discussed in the text, this is a generic model of a transmembrane transporter due to Hill [14] and based on the conformations of the protein E which uses the chemical gradient of M to pump L across the membrane against an adverse gradient. An ideal cycle would have no ‘slippage’: the link from EM to E^★M would not exist. As discussed in the text, two pathways: loop and slip have been marked. (b) The bond graph is geometrically the same as (a) but gives a precise description. (Es is used in place of E^★ for syntactical reasons).