Endocitoza

Endocitoza is a cellular process by which cells absorb molecules from outside the cell by engulfing them with their cell membrane. This process is crucial for various cellular functions, including nutrient uptake, waste removal, and cell signaling. Endocitoza can be broadly categorized into three main types: phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Phagocytosis, meaning "cell eating," involves the engulfment of large particles, such as bacteria or cellular debris, by the cell. This process is typically carried out by specialized cells like macrophages and neutrophils, playing a vital role in the immune system.

Pinocytosis, or "cell drinking," involves the uptake of fluids and dissolved solutes from the extracellular environment. This process is less specific than phagocytosis and occurs in most cell types, contributing to general nutrient absorption and fluid balance.

Receptor-mediated endocytosis is a highly specific mechanism where the cell membrane receptors bind to particular molecules, called ligands, on the outside of the cell. This binding triggers the formation of vesicles that internalize the receptor-ligand complexes. This process is essential for the uptake of specific molecules like cholesterol, hormones, and viruses.

Regardless of the type, endocitoza involves the invagination of the cell membrane to form a vesicle that encloses the external material. This vesicle then moves into the cytoplasm, where its contents can be processed or transported. Endocitoza is a dynamic and essential process for the survival and function of eukaryotic cells.