Practice question

Effective long-range aggregation requires non-continuous pulsatile emission of cAMP rather than steady gradient. Pacemaker cells spontaneously release cAMP every five to ten minutes, generating concentric waves degraded between pulses by extracellular phosphodiesterase PdsA. Intervals shorter than one to two minutes prevent receptor resensitization, while intervals longer than fifteen minutes degrade signal relay. Oscillatory frequency emerges from adaptation loop involving cAR1 phosphorylation, G protein activation, ACA refractory period, and PdsA recovery. Chemotacting amoebae move only during rising phase, pausing during falling phase, producing characteristic streaming pattern that efficiently gathers tens of thousands of cells toward center.