It has been long since we last did an article on a cell organelle. The last thing we did was ER or Endoplasmic Reticulum. Today, we will take a detailed look at yet another famous cell organelle – the Golgi Body. This article on Golgi Body facts will take a detailed look at the organelle and try to answer some of the commonest question related to it.
As you proceed through the article, you will find answers to the following questions:
- What is Golgi Body?
- Who discovered Golgi Body?
- What are the other names of Golgi Body?
- Where is Golgi Body located?
- Why are the Golgi Bodies also known as Dictyosomes?
- What is the Golgi Body made up of?
- What are the functions of Golgi Body?
These questions cover almost everything you need to learn about this unique cell organelle. So, without further ado, let us start with our article on Golgi Body facts.
Golgi Body Facts: 1-5 | What, Discoverer, Names
1. Golgi Body is a cell organelle and is present in cells of all higher animals and plants. It plays a very vital role in the functioning of the cell.
2. You may ask “why is the organelle so named?”. Well, it is actually named after the discoverer of the organelle. The person who discovered the organelle was known as Camillo Golgi.
3. Camillo Golgi was a neuroanatomist from Italy and he discovered the organelle somewhere in the late 19th century. To be exact, he discovered the organelle in 1897 and it was later named after him in year 1898. He found the organelle in the brain cells.
4. Golgi Body is also known by various other names. These names include Golgi Complex, Golgi Apparatus or, it is simply referred to as Golgi!
5. Golgi Body is also known as ‘Dictyosomes’ at times. Why it is so called will be described later in this article. Just continue reading to learn more about this organelle.
Golgi Body Facts: 6-10 | Where, Location, Structure
6. Where is Golgi Body found? Well, it is a cell organelle and hence, it is found inside a cell. The question is, “what type of cell?”. Golgi Complex is found in most of the eukaryotic cells. Just a quick reminder, eukaryotic cells have membrane-bound organelles.
7. Now the question is, ‘where exactly Golgi Body is located inside a cell?”. This is quite interesting. When it comes to its location inside the cell, there is no unique position in eukaryotic cells where the Golgi Body can be found.
9. In plants however, this is not true. In plants you cannot see Golgi ribbons and the Golgi stacks are not concentrated in the region of the centrosome.
10. What is the structure of the Golgi Body? The structure of the Golgi Body is quite complex. The whole of the apparatus is made of a series of compartments and contains two prominent networks.
Golgi Body Facts: 11-15 | Structure
11. The two networks present in the Golgi Body are known as the CGN and TGN. CGN stands for cis Golgi Network and TGN stands for trans Golgi Network.
12. The CGN and TGN networks are made up of a set of fused cisternae. Cisternae are nothing but flattened disks enclosed in membranes and appear very much like deflated balloons. These cisternae are also known by the name dictyosomes.
13. The CGN or cis Golgi Networks starts from the vesicular cluster budding off from the Endoplasmic Reticulum or ER.
14. It is interesting to note that somewhere between 4 and 8 cisternae club together to form a stack. There are between 40 and 100 such stacks that make up the Golgi Body found in mammalian cells.
15. All these stacks (collection of cisternae) are further divided into compartments. There are three compartments – cis, medial and trans.
Golgi Body Facts: 16-20 | Structure
16. The cis compartment consist of the cisternae that lie closest to the Endoplasmic Reticulum. The medial compartment consists of cisternae that form the central layers. The trans compartment consists of the cisternae that are farthest from the Endoplasmic Reticulum.
17. It is this cis compartment that makes up the CGN. The trans compartment makes up the trans Golgi Network or the TGN.
18. Thus essentially, the CGN and TGN are made up of the outermost cisternae. The outer face of the CGN is called cis face while the outer face of the TGN is called the trans face.
19. The cisternae are held together with what is known as matrix proteins. The whole Golgi Apparatus on the other hands is supported by microtubules present in the cytoplasm.
20. It is interesting to note that the structure and organization that has been described so far may differ in different eukaryotic cells. For instance, Golgi stacking is not found in Saccharomyces cerevisiae (yeast species) while it is seen in Pichia pastoris (another yeast species).
Golgi Body Facts: 21-25 | Structure and Functions
21. In plant cells, there is something interesting. Sets of cisternae or the dictyosomes do not stack up together to form the Golgi Complex. Instead, they stay dispersed in the Cytoplasm but basically do the same job as the Golgi Apparatus in animals. This is the reason why Golgi Body is often referred to as “Dictyosomes” but it specifically refers to plant cells.
22. Now, what is the function of Golgi Body? In simplest terms, it is responsible for receiving proteins produced by Endoplasmic Reticulum, processing those proteins and then packaging them in vesicles for transport to other places inside or outside the cell.
23. The question is, how do the proteins manufactured by ER get into the Golgi Complex. It is theorized that the cis face of the Golgi Complex has fenestrated cisternae (fenestrated means having apertures or perforations).
24. A very complex network of connecting (also called anastomosing) membrane tubules are attached to the fenestrated cisternae and cover those perforations. The perforations on the cis cisternae work as the docking sites.
25. The proteins carried out from Endoplasmic Reticulum using transport vesicles come and dock on the fenestrated cisternae.
Golgi Body Facts: 26-30 | Functions
26. At the docking station, the chaperone (supervisory) proteins and transport proteins are separated and taken back to the Endoplasmic Reticulum by the vesicles while the secretory products that arrived from the Endoplasmic Reticulum will move forward into the Golgi Complex and enter the medial cisternae.
27. At the medial cisternae, the secretory products undergo a set of processing and then move into the trans cisternae.
28. Further processing takes places at trans cisternae. Apart from further processing, the proteins and lipids are also sorted, labelled and packaged into vesicles for transportation to other places within the cell or outside the cell.
29. In the trans face the outermost membrane starts bulging and eventually pinch off to form the vesicles that transport the proteins and lipids processed by the Golgi Body to their ultimate destination.
30. The question here is, how does the protein molecules and secretory proteins that come from Endoplasmic Reticulum move inside the Golgi Complex? There are two major competing models for this. They are:
- Vesicular Transport Model
- Cisternal Maturation Model
Which model is correct is debatable. Nonetheless, let us take a look at each model…
Golgi Body Facts: 31-35 | Functions
31. The Vesicular Transport Model states that vesicles bud off from one cisterna and carry the protein and lipid molecules to the next cisterna where again new vesicles bud off and move forward with the processed material.
32. This Vesicular Transport Model states that budding vesicles also transport back chaperone and transport proteins back to Endoplasmic Reticulum. Thus, the cisternae are stationary.
33. The Cisternal Maturation Model states that the Golgi Apparatus is a dynamic organelle. In this model, it is proposed that the cis cisternae move forward and eventually mature into trans cisternae.
New cis cisternae on the other hand are formed by fusion of the vesicles that come from Endoplasmic Reticulum and doc at the cis face.
34. This Cisternal Maturation Model states that budding off of vesicles do take place but only for transporting proteins back to Endoplasmic Reticulum and not for transporting the proteins and lipids within the Golgi Complex.
35. It is believed that the different stacks in the Golgi Apparatus have an assorted collection of enzymes that allow stage-by-stage processing of cargo from the Endoplasmic Reticulum as the protein cargo continues to move from cisternae to cisternae.
Golgi Body Facts: 36-40 | Functions
36. It must be noted that all the enzymatic reactions that take place inside the Golgi Body actually happen near the membrane surface of the cisternae because that is precisely where all the enzymes stay anchored.
37. The enzymatic reaction or processing of proteins that takes place inside the Golgi Body are known as post-translational modification. Different modifications take place at different compartments of the Golgi Apparatus.
38. For instance, mannose residue removal takes place in both cis and medial compartments of Golgi Body. In the medial cisternae, addition of N-acetylglucosamine takes place along with mannose residue removal. In the trans cisternae, addition of sialic acid and galactose takes place. Also, carbohydrate and tyrosine sulfation takes place in the trans cisternae.
39. It is during this post-translational modification that a signal sequence is added to each protein and lipid molecule to determine the exact destination for the final processed product.
40. The shipping of the processed proteins take place by placing the labelled proteins into at least one of the following three types of vesicles:
- Lysosomal vesicles: These are the vesicles that will carry ribosomes and proteins that need to finally reach the lysosome after leaving the Golgi Body. Usually membrane proteins and digestive enzymes are carried by these vesicles.
- Secretory vesicles: These vesicles will carry those proteins that are meant to reach extracellular space but only when a signal is received for the release of those proteins. The vesicles stay in the cell until the signal is received. Once signal comes, the vesicles will move towards the cell membrane, fuse with it and release the content. Neurotransmitters are examples of such proteins that are carried by secretory vesicles.
- Exocytotic vesicles: Again, these vesicles carry proteins that will go into extracellular space. Once those proteins are packed into Exocytotic vesicles, these vesicles will immediately move towards cell membrane, fuse with the membrane and release the content. Example will be antibody that is released by activated plasma B cells.
Golgi Body Facts: Did You Know?
The Golgi Body is also responsible for the production of Lysosome that function as the digestive system of the cells. Lysosomes are called suicide bags!
In animal cells, Golgi Body disintegrates during mitosis and reform during telophase. This doesn’t happen in plant cells.
Golgi Body is known as the post office of the cell because of its function of modifying, sorting, labelling and packaging the proteins before shipping them.
The Golgi Complex was previously known by several names that includes:
- Golgi-Holmgren Apparatus
- Golgi-Kopsch Apparatus
- Golgi-Holmgren Ducts
When Golgi Body was first discovered by Camillo Golgi, scientific fraternity thought it was just an optical illusion.
The Golgi Body was discovered long before the functions of the organelle were understood. The early discovery was because of the relatively large size of the organelle.
Camillo Golgi used a staining technique for discovering the organelle. He called the technique as ‘Reazione Nera’, which literally translates into ‘Black Reaction’. Today the method is called ‘Golgi Stain’.
Image Credit: Kelvin Song | Public Domain