Critics once dismissed the Golgi apparatus as an optical illusion
In 1898 the Italian physician Camillo Golgi, studying nerve tissue, spotted a strange internal network in cells. Some colleagues suspected it was an artefact of his staining method. Better twentieth-century microscopes proved him right, and the structure, now named after him, turned out to be the cell's packaging and dispatch centre.
Golgi called his find the 'internal reticular apparatus'. It went by several names over the years before 'Golgi apparatus' came into use around 1910, appearing in print by 1913; 'Golgi complex' followed in 1956. Its size and distinctive shape made it one of the earliest organelles to be studied closely.
Structurally it is a stack of flattened membrane discs called cisternae, which form from vesicle clusters budding off the endoplasmic reticulum. A mammalian cell typically holds 40 to 100 stacks, each with four to eight cisternae, although some protists pack in as many as sixty. Each stack has an entry side, the cis face, and an exit side, the trans face. Enzymes are arranged in order along the way, early modifiers near the entrance and later ones toward the exit, so proteins undergo processing in sequence. A major job is glycosylation, attaching sugar units to proteins destined for export.
From the trans Golgi network at the far end, finished proteins are packed into vesicles headed for lysosomes, for secretion, or for the cell surface. The organelle therefore sits where the secretory, lysosomal and uptake pathways cross. Cells that export a lot have larger, more numerous Golgi; antibody-producing plasma B cells are a prominent example.
Layout differs across life. In mammals a single Golgi usually sits near the nucleus by the centrosome, its stacks linked by tubules that depend on microtubules; if those microtubules are taken apart experimentally, the stacks scatter through the cytoplasm. Plants organise theirs using actin cables, and their stacks appear to work independently. Among yeasts, Pichia pastoris has stacked Golgi, while baker's yeast, Saccharomyces cerevisiae, has scattered, unstacked ones. What stays constant is location: the Golgi always lies next to the exit sites of the endoplasmic reticulum.
Source: Golgi apparatus
