Which is a characteristic of exocytosis?

Exocytosis is a biological process through which cells expel materials, typically in the form of large molecules, from inside the cell to the extracellular environment. A key characteristic of exocytosis is that it requires energy, which is usually supplied in the form of ATP (adenosine triphosphate). This energy is necessary for the process to occur because it involves the movement of vesicles, which are membrane-bound structures that transport the substances to be expelled.

During exocytosis, these vesicles fuse with the plasma membrane of the cell, releasing their contents outside. The energy requirement is essential for the rearrangement of lipid bilayers and the conformational changes that proteins undergo, facilitating the fusion of the vesicle and the plasma membrane.

The other options are not characteristic of exocytosis. It does not occur in the nucleus, it involves vesicles that transport materials, and it is not a passive process like simple diffusion that would not require energy. Instead, it is an active process, highlighting its reliance on energy to function properly.