Endosytoitujen

Endosytoitujen refers to the process by which cells internalize external substances, such as molecules, particles, or even other cells, through invagination of the plasma membrane. This mechanism is fundamental to cellular function, enabling nutrient uptake, waste removal, and signal transduction. The term originates from the Greek words *endo* (within) and *phagein* (to eat), reflecting the cell’s ability to engulf external materials.

There are two primary types of endocytosis: phagocytosis and pinocytosis. Phagocytosis involves the ingestion of large particles or pathogens, such as bacteria or cellular debris, by extending pseudopodia to surround and engulf the target. This process is often associated with immune cells like macrophages. Pinocytosis, on the other hand, is a non-selective uptake of small fluid droplets and dissolved molecules, driven by the formation of small vesicles at the cell surface.

Receptor-mediated endocytosis is another specialized form, where specific receptors on the plasma membrane bind to ligands—such as hormones or growth factors—triggering vesicle formation. This method allows cells to selectively internalize particular molecules with high efficiency. The internalized vesicles then fuse with endosomes, which sort and transport contents to lysosomes for degradation or recycling back to the cell surface.

Endocytosis is tightly regulated and plays a critical role in maintaining cellular homeostasis, immune responses, and signal transduction pathways. Dysregulation of these processes has been linked to diseases, including neurodegenerative disorders and cancer, highlighting its importance in both normal physiology and pathology.