Here's a breakdown:

* Exocytosis is a process where a cell releases large molecules, such as proteins, hormones, and waste products, by fusing a vesicle containing the substance with the cell membrane.

* This fusion causes the vesicle to open up and release its contents outside the cell.

Here are some key points about exocytosis:

* Vesicles: Exocytosis involves small, membrane-bound sacs called vesicles that form inside the cell. These vesicles transport the substances that need to be released.

* Fusion: The vesicle membrane fuses with the cell membrane, effectively opening a temporary passageway for the contents to exit.

* Energy Requirement: Exocytosis requires energy, usually provided by ATP (adenosine triphosphate).

Examples of Exocytosis:

* Hormone secretion: Cells in the endocrine system use exocytosis to release hormones into the bloodstream.

* Neurotransmitter release: Neurons release neurotransmitters at synapses through exocytosis.

* Waste removal: Cells can remove waste products from their interior by exocytosis.

In contrast to exocytosis, the movement of large substances *into* a cell is called endocytosis.