Amplification by positive feedback A. Before receptor stimulation only a small number of effectors (inactive) bound to membrane B After receptor stimulation membrane bound effectors will be stimulated to produce more phospholipid second mesengers Images removed due to copyright considerations See Postma. M. and P.J. Van hastert C Local phospholipid increase "A diffusion-translocation model for gradient sensing leads to increased translocation of by chemotactic cells. Biophys J effector molecules 81,n0.3(Sep,2001):131423 D receptor can signal to more effectors leading to even more phospholipid production and further depletion of cytosolic effector molecules m k-m+P(x)Em: effector concentration in membrane P(x)=ko+kER (x)Em(x) Ec: effector concentration in cytosol.Amplification by positive feedback 4 A. Before receptor stimulation only a small number of effectors (inactive) bound to membrane B. After receptor stimulation, membrane bound effectors will be stimulated to produce more phospholipid second mesengers C. Local phospholipid inc rease leads to increased transloc ation of effector molecules D. receptor can signal to more effectors leading to even more phospholipid production and further depletion of cytosolic effecto r molecules. E m: effector concentration in membrane E c: effector concentration in cytosol. ( ) ( ) ( ) ( ) * 2 1 2 P x k k R x E x k m P x x m D dt dm o E m m = + − + ∂ ∂ = − Images removed due to copyright considerations. See Postma, M., and P. J. Van Haastert. "A diffusion-translocation model for gradient sensing by chemotactic cells." Biophys J. 81, no. 3 (Sep, 2001): 1314-23