Figure 4.

Harvesting antennae can explain high rates of H⁺ and Ca²⁺ extrusion. The standard model of transport assumes that molecules reach their binding sites by random diffusion through the aqueous phase. However, because of the low prevailing concentrations of H⁺ and Ca²⁺, the probability of this occurring is too small to sustain the observed rates of translocation. A harvesting antenna increases the binding probability, allowing the aqueous phase to feed the transporter at high rates.