Exocytosis

Exocytosis is a cellular process where cells eject waste products or chemical transmitters (such as hormones) from the interior of the cell.

Exocytosis is similar in function to endocytosis but working in the opposite direction.

There are five steps to exocytosis:

In this first step, the vesicle containing the waste product or chemical transmitter is transported through the cytoplasm towards the part of the cell from which it will be eliminated.

As the vesicle approaches the cell membrane, it is secured and pulled towards the part of the cell from which it will be eliminated.

In this step, the vesicle comes in contact with the cell membrane, where it begins to chemical and physically merge with the proteins in the cell membrane.

In those cells where chemical transmitters are being released, this step involves the chemical preparations for the last step of exocytosis.

In this last step, the proteins forming the walls of the vesicle merge with the cell membrane and breach, pushing the vesicle contents (waste products or chemical transmitters) out of the cell. This step is the primary mechanism for the increase in size of the cell’s plasma membrane.

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• Biology Quiz: Cell Membranes
• My Cell Membranes
• Plasma Membrane – Plant Cells
• Plasma Membrane – Animal Cell
• Passive Transport
• Osmosis in an Animal Cell
• Osmosis in a Plant Cell
• Membrane Proteins
• Lipid Bilayer
• Exocytosis
• Endocytosis
• Diffusion Through a Membrane
• Carrier Proteins
• Active Transport