What is the term for the secretion of cellular products out of the cell?

The correct term for the secretion of cellular products out of the cell is exocytosis. This is a process where intracellular vesicles fuse with the plasma membrane and release their contents into the extracellular environment. Exocytosis is essential for various cellular functions, such as the release of neurotransmitters from nerve cells, the secretion of hormones, and the expulsion of waste products from the cell.

In this process, materials like proteins or other molecules packaged in vesicles are transported to the cell membrane, where the vesicle membrane merges with the cell membrane, allowing the contents to be expelled outside. Understanding exocytosis is crucial in contexts such as cellular signaling and the functioning of endocrine and exocrine glands.

The other options mentioned relate to different cellular transport mechanisms. Endocytosis refers to the process of taking in materials into the cell, filtration is the movement of water and solutes through a membrane due to pressure differences, and active transport involves the movement of substances against their concentration gradient, typically requiring energy. These processes serve distinct roles within the cell that do not correspond to the secretion function described in the question.