In vesicular transport, what happens during the fusion step?

During the fusion step of vesicular transport, the membranes of the vesicle and the target organelle or cell merge. This is a crucial part of the transport process because it allows the contents of the vesicle to be delivered to the target site. The fusion of the membranes is facilitated by specific proteins that promote the merging of bilayers, usually involving components called SNAREs, which ensure that the right vesicles fuse with the correct target membranes.

The process effectively enables the transfer of cargo, which can include proteins, lipids, or other molecules, from one compartment to another within the cell. After fusion, the contents of the vesicle are integrated into the target membrane or released into the lumen of the target compartment, depending on the nature of the transport event. This step is critical for a wide variety of cellular functions, including secretion, uptake of nutrients, and membrane recycling.