<prompt> Which of the following is the regulated membrane transfer?Insulin secretion by pancreatic b-cellO2 diffusion across the respiratory membraneFolate entry into the cellsMucus secretion by goblet cells  <response>: Regulated membrane transfer is the transpo acrossthrough the membrane which is regulated by a specific signal or ligand. Exocytosis is a regulated membrane transfer. E.g. Neurotransmitter secretion at a synaptic junction. The transmitter is released only when the signalimpulse arrives at the nerve terminal. Insulin secretion, by exocytosis, occurs when a signal, i.e. increased blood glucose, is delivered to the pancreatic beta cell. Options B, C, and D do not occur after a specific signalling ligand has arrived at those respective cells. 