endotsüüsi

Endotsütoos is a cellular process by which cells absorb molecules from outside the cell by engulfing them with their cell membrane. This process is essential for a variety of cellular functions, including nutrient uptake, immune response, and signal transduction. Endotsütoos is a form of active transport, meaning it requires energy in the form of ATP.

There are several types of endotsütoos, including phagotsütoos, pinotsütoos, and receptor-mediated endotsütoos. Phagotsütoos, also known as "cell eating," is the process by which cells engulf large particles, such as bacteria or cellular debris. Pinotsütoos, or "cell drinking," involves the uptake of fluids and dissolved solutes. Receptor-mediated endotsütoos is a more specific process that relies on the presence of specific receptor proteins on the cell surface. These receptors bind to particular molecules, triggering the invagination of the cell membrane and the formation of a vesicle containing the bound molecule.

Once the vesicle is formed inside the cell, it can fuse with lysosomes, which contain enzymes that break down the ingested material. The resulting molecules are then released into the cytoplasm for the cell's use. Endotsütoos plays a critical role in maintaining cellular homeostasis and in mediating interactions between cells and their environment. For example, immune cells use phagotsütoos to clear pathogens, and nerve cells use it to recycle neurotransmitters.