Here's a breakdown:

* Secretory proteins are proteins synthesized by ribosomes on the rough endoplasmic reticulum (ER). These proteins are destined for secretion outside the cell.

* Transport vesicles bud off from the ER and Golgi apparatus, carrying the secretory proteins.

* Fusion with the plasma membrane occurs when the transport vesicle's membrane merges with the cell's outer membrane.

* Exocytosis is the process of releasing the secretory proteins into the extracellular space.

This process is essential for many cellular functions, including:

* Hormone secretion: Cells release hormones like insulin or growth hormone.

* Neurotransmitter release: Nerve cells release neurotransmitters to communicate with other cells.

* Enzyme secretion: Cells release digestive enzymes like amylase.

* Waste removal: Cells excrete waste products.

Let me know if you have any other questions!