The transport of proteins out of the cell is termed exocytosis. Which of the following statement(s) is/are true concerning this process?

a.Secretory vesicles fuse with the plasma membrane

b.The process can occur in either a constitutive or regulated process

c.A regulated secretion is triggered by a stimulus, most likely a hormone or a neurotransmitter

Transport vesicles that bud off the Golgi network carry both material to be secreted from the cell and protein destined to become components of the plasma membrane. These vesicles can fuse with the plasma membrane in a process termed exocytosis. Vesicular transport to the cell surface can be divided into two components, constitutive and regulated secretion. Regulated secretion occurs in cells secreting digestive enzymes, hormones and other regulatory molecules, and neurotransmitters. In regulated secretion, the material to be secreted is sorted in a storage vesicle or granule; fusion with the plasma membrane in exocytosis then takes place in response to external stimulation. Regulated secretion is triggered in most cases by a hormone or neurotransmitter. The ensuing process is termed stimulus-secretion coupling. In most cases the coupling involves an increase in cytoplasmic concentration of Ca++, but may also involve generation of diacylglycerol or production of cyclic AMP which activate kinases or phosphatases.