theGolgi

The Golgi apparatus, also known as the Golgi complex, is a membrane-bound organelle of the eukaryotic cell that forms part of the endomembrane system. It was first described by Camillo Golgi in 1898. In many animal cells, it appears as a series of flattened, stacked membrane-bound sacs called cisternae, located near the nucleus and the endoplasmic reticulum.

The Golgi exhibits polarity with a cis face oriented toward the endoplasmic reticulum and a trans face facing the plasma membrane or lysosomes. Cargo arrives from the ER in vesicles, passes through typically three to six cisternae (cis, medial, trans), and undergoes enzymatic processing. Enzymes within the cisternae mediate modifications such as glycosylation, sulfation, and phosphorylation. The organelle also serves as a sorting hub, directing proteins and lipids to lysosomes, the plasma membrane, or for secretion. In many cells, the Golgi participates in the assembly of complex macromolecules like proteoglycans.

Vesicular trafficking to and from the Golgi involves coat proteins and motor proteins. Two conceptual models describe its operation: the vesicular transport model (cargo moves between stable cisternae) and the cisternal maturation model (cisternae themselves mature from cis to trans). The Golgi is dynamic and varies in organization among cell types and organisms; plant cells often display multiple, separate Golgi stacks. Proper Golgi function is essential for protein maturation, lipid modification, and targeted delivery within the cell.