We explain what the Golgi apparatus is, what its structure is like and what its functions are. Also, its characteristics and diseases.
What is the Golgi Apparatus?
The Golgi apparatus is an organelle contained in all eukaryotic cells (those that have a defined nucleus in their cytoplasm) and that form part of the endomembrane system.
Is about a vital organelle in the synthesis of many proteins and lipids of the cell, which functions as a packaging plant: it synthesizes, packages and distributes the substances generated by the cell to their respective destinations in the cytoplasm.
Cells may have one or more of these Golgi apparatuses. (in fact, plants have hundreds of them), generally located near the cell nucleus and the endoplasmic reticulum, in the cytoplasm.
Depending on the cell, Each device can contain a variable number of tanks, that is, “bags” stacked to contain proteins or lipids. In this way, it is an essential organelle for cellular life and for the fulfillment of organic synthesis.
See also: Prokaryotic cell.
Name Golgi apparatus
The name of the Golgi apparatus comes from its discovery at the beginning of the 20th centurywhen the Italian scientist Camillo Golgi, winner of the Nobel Prize in Medicine in 1906, managed to describe them in great detail, based on the initial observations in 1897 by the Spaniard Santiago Ramón y Cajal, with whom he shared the award.
The use of the electron microscope from 1950 onwards confirmed Golgi’s descriptions quite accurately.
Dictyosomes of the Golgi apparatus
The Golgi apparatus consists of dictyosomes, which They are a set of membranous sacculesthat is, submicroscopic, flattened and stacked containers, surrounded by a tubular network and a set of vesicles.
Inside each dictyosome are the cisternae where proteins are “packaged”. In fact, talking about dictyosomes, the Golgi apparatus or the Golgi system is basically talking about the same thing.
Golgi apparatus size
The size of the dictyosomes and cisternae of the Golgi apparatus is variable, depending on the type of cell, the species and the metabolic moment Of the same. It is generally estimated to measure between 1 and 3 microns in diameter.
Structure of the Golgi apparatus
The Golgi apparatus encompasses three distinct functional regions:
- Cis-golgi region. The innermost portion, and closest to the rough endoplasmic reticulum (RER), from which the vesicles with newly synthesized proteins come.
- Medial region. A transition zone between the Cis and Trans regions.
- Trans-Golgi region. It is located closer to the plasma membrane, and it is there where the membranes are modified so that each protein and lipid is sent to its specific destination.
However, the full functioning of the Golgi apparatus has not yet been fully understood.
Functions of the Golgi apparatus
The general function of the Golgi apparatus is to “package” and “label” each protein vesicle so that it can be sent to its destination successfully, just as a central product packaging plant does.
In this sense, the Golgi apparatus Check that the product has no defectswhich is complete and assembled, joining simple molecules to form other complex ones and identifying them accordingly according to their destination: other cell organelles or the cell membrane, to be secreted into the environment.
Other functions of the Golgi apparatus include:
- Absorb substances from the cytoplasm. Such as water, sugars or lipids, especially those derived from the formation of secretory vesicles.
- Form secretory vesicles. Create the protein sacs that transport their contents out of the cell.
- Create enzymes. Numerous enzymes originate in this organelle, since they are proteins with specific functions.
- Create specialized substances. To contribute to the cell membrane, the constitution of specialized cells (such as sperm), proteins such as milk, etc.
- Secrete glycoproteins. Proteins that contain carbohydrates (sugars) are formed inside.
- Produce lysosomes. Organelles responsible for cellular digestion.
Types of gallbladder
Transport vesicles that cross the Golgi apparatus can be of the following types:
- Constitutive. They contain proteins whose destination is outside the cell, through constitutive secretion (exocytosis) that takes place in the plasma membrane.
- Regulated. Secretion vesicles that are also destined for the outside of the cell, but not immediately: they will be stored in the cell waiting for their triggering stimulus to occur. This process is called regulated secretion.
- Lysosomal. Its destination is lysosomes: organelles generated by the Golgi system itself, responsible for breaking down external substances that enter the cell (cellular digestion).
Golgi apparatus transport mechanism
The exact mechanism of how proteins move through the Golgi apparatus is still unclear. But there are two main hypotheses regarding how it happens:
- Cistern maturation model. The generation of new cisterns would “push” the old ones through the device.
- Vehicular transport model. This theory assumes the Golgi apparatus as a stable and static entity, and that the movement of the vesicles is due rather to the nature of the proteins inside them.
Function of lysosomes
Lysosomes generated by the Golgi apparatus contain hydrolytic and proteolytic enzymescapable of breaking down material of extracellular or intracellular origin, that is, responsible for cellular digestion.
Lysosomes are bags of enzymes that, If they were released inside the cell, they would completely destroy it. Therefore, these organelles have a specialized membrane that prevents this. Lysosomes are common to animal cells, but not to plant cells.
More in: Lysosomes.
Importance of the Golgi apparatus
This apparatus It is of vital importance in the protein generation circuit of cells and, by extension, of living beings. It serves as a link between the interior of the cell (the nucleus and the endoplasmic reticulum, where proteins are produced) and the exterior of the cell. It is a crucial biochemical transport mechanism.
Diseases related to the Golgi apparatus
There are some cases in which defects in the Golgi apparatus result in diseases such as Mucolipidosis II, a disease that affects the protein identification mechanism of the Golgi apparatus, so cellular digestion cannot take place properly and the lysosomes fill with undigested material. It is a congenital disease with fatal consequences, which does not allow life to exceed 7 years of age.
Many other conditions under current study are thought to originate from defects in the Golgi apparatus, such as Pelizaeus-Merzbacher disease, Angelman syndromewrinkled skin syndrome and Ducheme muscular dystrophy, among others.