Sejtfelszívódás

Sejtfelszívódás, also known as cellular uptake or endocytosis, is a fundamental biological process by which cells absorb molecules from the extracellular environment. This process is crucial for nutrient acquisition, waste removal, and communication between cells. There are several distinct mechanisms of sejtfelszívódás, each suited for different types of cargo.

Phagocytosis, meaning "cell eating," involves the engulfment of large particles such as bacteria, cellular debris, or even entire cells. The cell membrane extends outwards, forming pseudopods that surround and internalize the particle within a large vesicle called a phagosome. This process is vital for the immune system's defense against pathogens.

Pinocytosis, or "cell drinking," is a more general form of uptake where the cell ingests fluids and dissolved solutes. The cell membrane invaginates, forming small vesicles that pinch off into the cytoplasm. This mechanism continuously samples the extracellular fluid for smaller molecules.

Receptor-mediated endocytosis is a highly specific process that utilizes receptors on the cell surface to bind to particular molecules. Once the ligand binds to its receptor, the cell membrane invaginates at that specific location, forming a coated vesicle containing the bound molecules. This allows cells to selectively internalize essential substances like cholesterol or hormones.

Regardless of the specific mechanism, the internalized material is enclosed within a membrane-bound vesicle. These vesicles then fuse with lysosomes within the cell, where the contents are broken down and processed, or they may be transported to other cellular compartments. Sejtfelszívódás is a dynamic and essential process for cellular function and survival.