There are two major types of cells: prokaryotic and eukaryotic cells. The latter have a clearly defined nucleus. The Golgi apparatus is the manufacturing and shipping center of a eukaryotic cell.
The Golgi apparatus, sometimes called the Golgi complex or Golgi body, is responsible for manufacturing, warehousing, and shipping certain cellular products, particularly those from the endoplasmic reticulum (ER). Depending on the type of cell, there can be just a few complexes or there can be hundreds. Cells that specialize in secreting various substances typically have a high number of Golgi.
Italian cytologist Camillo Golgi was the first to observe Golgi apparatus, which now bears his name, in 1897. Golgi used a staining technique on nervous tissue that he called internal reticular apparatus.
While some scientists doubted Goglis findings, they were confirmed in the 1950s with the electron microscope.
- In eukaryotic cells, the Golgi apparatus is the manufacturing and shipping center of the cell. The Golgi apparatus is also known as the Golgi complex or Golgi body.
- A Golgi complex contains cisternae. Cisternae are flat sacs that are stacked in a semicircular, bent formation. Each formation has a membrane to separate it from the cytoplasm of the cell.
- The Golgi apparatus has several functions, including modification of several products from the endoplasmic reticulum (ER). Examples include phospholipids and proteins. The apparatus can also manufacture its own biological polymers.
- The Golgi complex is capable of both disassembly and reassembly during mitosis. In the early stages of mitosis, it disassembles while it reassembles in the telophase stage.
A Golgi apparatus is composed of flat sacs known as cisternae. The sacs are stacked in a bent, semicircular shape. Each stacked grouping has a membrane that separates its insides from the cells cytoplasm. Golgi membrane protein interactions are responsible for their unique shape. These interactions generate the force that shapes this organelle.
The Golgi apparatus is very polar. Membranes at one end of the stack differ in both composition and in thickness from those at the other end. One end (cis face) acts as the receiving department while the other (trans face) acts as the shipping department. The cis face is closely associated with the ER.
Molecule Transport and Modification
Molecules synthesized in the ER exit via special transport vehicles that carry their contents to the Golgi apparatus. The vesicles fuse with Golgi cisternae releasing their contents into the internal portion of the membrane. The molecules are modified as they are transported between cisternae layers.
It is thought that individual sacs are not directly connected, thus the molecules move between cisternae through a sequence of budding, vesicle formation, and fusion with the next Golgi sac. Once the molecules reach the trans face of the Golgi, vesicles are formed to ship materials to other sites.
The Golgi apparatus contains processing enzymes, which alter molecules by adding or removing carbohydrate subunits. Once modifications have been made and molecules have been sorted, they are secreted from the Golgi via transport vesicles to their intended destinations. Substances within the vesicles are secreted by exocytosis.
Some of the molecules are destined for the cell membrane where they aid in membrane repair and intercellular signaling. Other molecules are secreted to areas outside of the cell.
Transport vesicles carrying these molecules fuse with the cell membrane releasing the molecules to the exterior of the cell. Still other vesicles contain enzymes that digest cellular components.
These vesicle form cell structures called lysosomes. Molecules dispatched from the Golgi may also be reprocessed by the Golgi.
Golgi Apparatus Assembly
The Golgi apparatus or Golgi complex is capable of disassembly and reassembly. During the early stages of mitosis, the Golgi disassembles into fragments which further break down into vesicles.
As the cell progresses through the division process, the Golgi vesicles are distributed between the two forming daughter cells by spindle microtubules. The Golgi apparatus reassembles in the telophase stage of mitosis.
The mechanisms by which the Golgi apparatus assembles are not yet understood.
Other Cell Structures
- Cell Membrane: protects the integrity of the interior of the cell
- Centrioles: help to organize the assembly of microtubules
- Chromosomes: house cellular DNA
- Cilia and Flagella: aid in cellular locomotion
- Endoplasmic Reticulum: synthesizes carbohydrates and lipids
- Lysosomes: digest cellular macromolecules
- Mitochondria: provide energy for the cell
- Nucleus: controls cell growth and reproduction
- Peroxisomes: detoxify alcohol, form bile acid, and use oxygen to break down fats
- Ribosomes: responsible for protein production via translation