What is the difference between constitutive and regulated secretion?

Constitutive secretion is a process that occurs continuously, where substances are secreted from cells without the need for specific signals or stimuli. This mechanism is crucial for maintaining normal cellular functions and involves the ongoing delivery of proteins and lipids to the cell's exterior, as well as contributing to the formation of the extracellular matrix.

On the other hand, regulated secretion is characterized by its dependence on specific stimuli, such as hormonal or neuronal signals. This type of secretion is often associated with the storage of signaling molecules (like neurotransmitters or hormones) in specialized secretory vesicles. When the appropriate signal is received, these vesicles fuse with the plasma membrane, allowing the contents to be released rapidly and in a controlled manner.

Understanding this distinction is fundamental in cell biology, particularly in contexts where timing and regulation of substance release are critical for physiological responses. The key difference lies in the continuous nature of constitutive secretion versus the prompt, event-triggered aspect of regulated secretion.