What is Exocytosis?
Exocytosis is the process by which cells move materials from within the cell into the extracellular fluid. It is a form of active transport where a vesicle, a small membrane-bound sac containing the material, fuses with the cell membrane and releases its contents to the outside.
Section 2: The Mechanism of Exocytosis
The process begins when materials, such as proteins or hormones, are packaged into transport vesicles, often by the Golgi apparatus. This vesicle then travels to the cell's surface. Upon reaching the plasma membrane, the vesicle's membrane merges with the cell's outer membrane, creating an opening through which the contents are expelled from the cell.
Section 3: A Practical Example
A classic example of exocytosis is the release of neurotransmitters in the nervous system. When a nerve impulse reaches the end of a neuron, vesicles containing neurotransmitters fuse with the neuron's cell membrane, releasing these chemical messengers into the synapse to transmit the signal to the next neuron.
Section 4: Why is Exocytosis Important?
Exocytosis is crucial for many vital biological functions. It enables cells to secrete hormones for bodily regulation, release neurotransmitters for cell-to-cell communication, expel waste products, and deliver proteins and lipids to the cell membrane for repair and growth.