Golgi Apparatus Definition, Structure, Functions, and Diagram

Golgi Apparatus Overview

The principal purpose for Golgi’s main function is Golgi apparatus is to transfer vesicles or packets of different cell products, to various areas of the cell. The Golgi is also involved in tagging vesicles by sugar molecules and proteins which act as identifiers of the vesicles, allowing them to be delivered to the right destination. The organelle can also be referred to as Golgi body. Golgi complex, or Golgi body.

In general, proteins and other cells are made in the endoplasmic Reticulum. The rough endoplasmic retina contains several ribosomes that assemble proteins based on instructions inside messenger RNA. Through the rest of the endoplasmic retina proteins are folded and altered. Once they are in to the Golgi apparatus, further modifications are carried out. Then, the proteins are contained in vesicles that can be “labeled” by other proteins and molecules. The vesicles are released , and dependent on their labels or tags they are transported to the correct position within the cell by the cell’s cytoskeleton.

Discovery

Due to its huge dimensions and unique structure Due to its size and distinctive structure, due to its distinctive shape and size, Golgi apparatus was among the first organelles examined in detail. It was first discovered during the year 1898 by Italian doctor Camillo Golgi in the course of an investigation into the nerve system. After first seeing it with a microscope Golgi referred to the structure as an apparato reticolare internalo (“internal retinal apparatus”). Many doubted the findings initially, insisting that this appearance was an optical illusion produced by the observation technique employed by Golgi. After the advent of modern microscopes during the 20th century and the discovery was confirmed. The first reports of the Golgi apparatus were identified with various names such as”Golgi-Holmgren apparatus” “Golgi-Holmgren apparatus”, “Golgi-Holmgren ducts” as well as “Golgi-Kopsch apparatus”. The expression “Golgi apparatus” was used in the year 1910 and first appeared in scientific publications in 1913. The term “Golgi complex” was introduced in 1956.

Golgi Apparatus Definition

The Golgi apparatus, also known as the Golgi body, or Golgi complex, or just Golgi is a cell-based organelle that is found in the majority of the cells in eukaryotic species. It is known as the production and transport center of cells. Golgi plays a role in packaging proteins prior to when they are shipped to their destinations. Organelles aid in the processing and packaging of macromolecules such as proteins and lipids produced by cells and thus serve as the ‘postoffice for the cell. Golgi apparatus was first discovered in 1898 by the Italian biologist named Camillo Golgi.

Characteristics of Golgi Apparatus

• The Golgi apparatus, also known as Golgi, is an organelle that was discovered in 1898 by the Italian physician Camilo Golgi. It is also one of the GERL complex’s components.
• In eukaryotic cells, various chemicals, such as proteins, are secreted via the Golgi apparatus. This organelle is known as dictyosome in plants.
• In flagellate protozoa, this structure is known as the parabasal body. Golgi complex is the collective term for all Golgi apparatus in a cell.
• The Golgi apparatus comprises cisternae. These cisternae are derived from the endoplasmic reticulum-derived vesicles. There are around 40 to 100 stacks of cisternae in mammals.
• The stacks consist of fused, flattened cisternae connected via tubular (microtubules) connections. Without these microtubules, the Golgi consists of separate discs.
• In plants, actin instead of microtubules connects the stacks. Its position varies inside the cell. It is typically found near to the nucleus in mammals, notably in the centrosomal area. It is not concentrated at the centrosomal region in plants.
• Yet, the majority of Golgi in eukaryotic cells are located close to endoplasmic reticulum exit sites. 1 In addition, the Golgi cisternal stack in all eukaryotes has both cis and trans faces. The cis face is the entrance, whereas the trans face is the exit. They have distinct metabolic enzymes.
• In the cis face cisternae, the enzymes present are those responsible for early protein modifications, whereas in the trans face, the enzymes are responsible for the final protein modification.
• Golgi enzymes are membrane-anchored, whereas endoplasmic reticulum enzymes are located in the lumen. Hence, enzymatic reactions occur adjacent to the membrane surfaces of the Golgi, where enzymes are situated, during protein modification activities.

Golgi Apparatus Location

It is believed that the Golgi apparatus is located between the endoplasmic retina and cell membrane. Most of the time it appears that the Golgi is thought to extend the endoplasmic retina that is a little smaller and appears smoother. However the Golgi apparatus could be confused with smooth endoplasmic reticulum. While they appear similar but they are not identical. Golgi is an individual organelle with distinct functions.

Structure of Golgi Apparatus

Under the microscope of electrons under the electron microscope, the Golgi apparatus can be seen to consist of of flattened structures that house several vesicles with secretory granules. It is believed that the Golgi apparatus is morphologically like that of animals and plants. But, it is incredibly pluralistic: in some cells it appears to be compact and confined, while in other types it appears scattered in a it appears reticular (net-like). In general however, Golgi apparatus is an intricate array of interconnected tubules, vesicles and cisternae.

A. Cisternae

The simplest part that makes up the Golgi apparatus. It is called the cisterna. Cisternae (about 1 millimeters in size) are flat, central with saucer-like, plate-like, or flattened compartments which are contained in stacked bundles or parallel bundles one over one another. Within every stack, cisternae are separated by 20-30 nm, which might contain rod-like components or fibers. Every cisternae stack forms an dictyosome that could contain five to six Golgi cisternae within animal cells, and twenty or more cisternae inside plant cells.

Every cisterna is bordered with a unidirectional membrane (7.5 Nm thick) with an elongated lumen that ranges in width between 500 and 1000 nm. The edges of every cisterna have been gently curled to ensure that the whole dictyosome of the Golgi apparatus has an appearance of a bow. The cisternae that are located at the convex side of the dictyosome have the proximal, forming or cis face and cisternae that are at the concave ends of the dictyosome are the trans-face, distal or maturing.

B. Tubules

A vast array of tubules anastomosing vesicles (30 to 50 nanometers in diameter) are surrounded by the dictyosome and extend out from it. In actuality the peripheral region that surrounds the dictyosome has been the fenestrated (lace-like) in its structure.

C. Vesicles

The vesicles (60 millimeters in diameter) are composed of three types:

1. Transitional vesicles are tiny membrane-bound vesicles, which are believed to develop as blebs arising from in the transitional ER to move and then converge onto the cis surface of Golgi which is where they join to create new cisternae.
2. Secretory vesicles vary in size and are membrane-limited vesicles that drain from the margins of cisternae in Golgi. They typically occur between the maturing surface of Golgi and the plasma membrane.
3. Clathrin-coated vesicles are spherical pro with a diameter of 50 millimeters diameter and having rough surfaces. They are located at the edges of the organelle. They are usually on the ends of single tubules. They differ in morphology from secretory vesicles. These clathrin-coated vessels are thought to be involved in the intracellular movement of membranes as well as secretory substances, i.e., between ER and Golgi and connecting the GELR region as well as between the endosomal and lysosomal compartments.

Functions of Golgi Apparatus

1. The vesicles of the Golgi are frequently called”the “traffic police” of the cell. They play an essential function in sorting many cells’ proteins as well as membrane components, as well as the direction of these components to their appropriate places of travel.
   • To fulfill this purpose To perform this function, Golgi vesicles have various sets of enzymes within different kinds of vesiclesthat is trans, middle and trans-cisternae. These enzymes modify and interact with secretory proteins flowing across the Golgi lumen, or glycoproteins and membrane proteins that are present transiently in Golgi membranes when they move towards their ultimate locations.
   • The Golgi apparatus acts as the assembly facility in the cell. The raw materials are routed into the Golgi apparatus prior to being taken out of the cell.
2. In mammals In animals, in animals, the Golgi device is involved with the exocytosis and packaging of the following substances :
   • Zymogen of exocrine pancreatic cells;
   • Mucus (=a glycoprotein) secretion by goblet cells of the intestine ;
   • Lactoprotein (casein) secretion by mammary gland cells (Merocrine secretion) ;
   • The secretion of substances (thyroglobulins) of the hormone thyroxine by thyroid cells
   • Secretion of tropocollagen as well as collagen;
   • Melanin granules are formed and other pigments as well as
   • Formation of vitelline and yolk membranes of growing primary oocytes.
3. It also contributes to the creation of cell organelles, including the plasma membrane and lysosomes cortical granules from many oocytes.
4. They also play a role in the movement of lipid molecules throughout the cell.
5. The Golgi complex is also involved in the creation of proteoglycans. Proteoglycans are a class of molecules that are found inside the extracellular matrix cells of animals.
6. It’s also a significant source of the production of carbohydrates. They are also involved in glycosaminoglycans synthesis, Golgi is able to attach to these polysaccharides, which later joins with a protein in the endoplasmic Reticulum to create proteoglycans.
7. The Golgi is involved in the process of sulfation certain molecules.
8. This process involves phosphorylation molecules through the Golgi requires the entry from ATP through the lumen Golgi.
9. In the plant, Golgi apparatus is mainly involved in the production of the both cell wall (e.g. the formation and export of glycoproteins monomers, lipids, and pectins for hemicellulose, cellulose the lignin, and so on.)

Golgi Apparatus Assembly

The Golgi apparatus, or Golgi complex is capable of disassembly as well as disassembly and. In the beginning stages of mitosis it is when the Golgi is broken into pieces, which are then broken down into vesicles.

When the cell is progressing in the division procedure the Golgi vesicles are dispersed between the two cells that are forming daughter cells through spindle microtubules. The Golgi apparatus is reassembled in the telophase stage in mitosis.

The mechanisms through which the Golgi apparatus is assembled aren’t yet fully understood.

Golgi Apparatus in Plant Cells

This article is primarily about the functioning in the Golgi apparatus inside the animal cell, cells in plants too possess the Golgi apparatus. Plant cells could have hundreds of these organelles.

In plant cells the Golgi apparatus is also responsible for the task of synthesizing the main polysaccharide molecules that help to form the cell’s wall. In order to do this, plants usually contain of Golgi bodies than a human cell. Additionally, plant cells are not able to contain the lysosomes. These digestive organelles are replaced by the plant by the central vacuole, which functions as a huge lysosome as also an organelle that can store water. Therefore, a lot of vesicles that originate from the Golgi bodies of plants are moved into the vacuole, where they combine their contents with this huge organelle.

Theory of Golgi Apparatus Function

The most popular theory about the way in which the Golgi apparatus develops is the Cisternal maturation model. The theory suggests that the sacs themselves are likely to migrate from the cis towards the trans side of the apparatus as time passes. New sacs form near the endoplasmic-reticulum. The sacs “age” as they move toward the trans-face and the Golgi apparatus, and their product matures to full maturity.

Specific Products

It might seem as if there will never be enough lipids to create the constant circulation of cell membranes that are required to create vesicles of transport between the endoplasmic-reticulum as well as the Golgi apparatus. There are however, constantly cells with membranes that are created to be recycled and reused by endoplasmic-reticulum the Golgi apparatus and lysosomes and other organelles inside the cell and the cell’s membrane that surrounds it. It is believed that the Golgi apparatus and the endoplasmic reticulum are both involved in the production of new cell membranes, as well as recycle cell membranes of vesicles through connecting two membranes as the vesicles absorb.

The Golgi is also responsible for the creation of Lysosomes. These sacs contain digestive materials. They are separated of the Golgi apparatus and are utilized to process substances that have been phagocytized to digest organelles that are no longer functioning. Lysosomes transport raw materials to the endoplasmic Reticulum.

Facts about Golgi Apparatus

1. The Golgi apparatus is an organelle found in eukaryotic cells, named after its discoverer, Italian biologist Camillo Golgi.
2. It is made up of a series of flattened, membrane-bound sacs known as cisternae, which are stacked on top of each other.
3. The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for transport to their final destinations within the cell or outside of it.
4. The Golgi apparatus plays a critical role in the secretion of enzymes and hormones, as well as the formation of lysosomes, which are important for intracellular digestion.
5. The Golgi apparatus is particularly prominent in cells that produce and secrete large amounts of proteins, such as glandular cells and immune cells.
6. The Golgi apparatus is closely connected to the endoplasmic reticulum, another organelle involved in protein synthesis and modification.
7. The Golgi apparatus is made up of several distinct regions, each with specific functions, including the cis-Golgi network, medial Golgi, and trans-Golgi network.
8. The Golgi apparatus also plays a role in glycosylation, the process by which sugars are added to proteins and lipids to modify their structure and function.
9. Certain viruses, such as the influenza virus, hijack the Golgi apparatus to facilitate their replication and assembly.
10. Mutations in genes encoding proteins involved in the function and organization of the Golgi apparatus have been linked to a number of diseases, including some types of cancer and neurodegenerative disorders.

What happens to proteins as they pass through the golgi apparatus?

Proteins undergo a variety of modifications as they pass through the Golgi apparatus. The Golgi apparatus is involved in processing, modifying, and sorting proteins synthesized in the endoplasmic reticulum (ER) before they are transported to their final destinations within the cell or outside of it.

Here are some of the modifications that occur to proteins as they pass through the Golgi apparatus:

1. Glycosylation: Sugars are added to proteins to modify their structure and function. This process is called glycosylation, and it is a critical modification that occurs in the Golgi apparatus. Glycosylation can affect the folding, stability, and activity of proteins.
2. Phosphorylation: Proteins can be phosphorylated, meaning that a phosphate group is added to them. This modification can change the activity or location of a protein within the cell.
3. Sulfation: Proteins can also be sulfated in the Golgi apparatus, which involves adding a sulfate group to the protein. This modification is important for the function of some proteins, such as extracellular matrix proteins.
4. Sorting: The Golgi apparatus is also involved in sorting proteins and packaging them into vesicles for transport to their final destinations. Proteins can be sorted based on their destination, such as the plasma membrane or lysosomes.

Overall, the Golgi apparatus plays a crucial role in processing, modifying, and sorting proteins synthesized in the endoplasmic reticulum. The modifications that occur in the Golgi apparatus can affect the function, location, and stability of proteins within the cell.

What do the rough endoplasmic reticulum, golgi apparatus, and lysosomes have in common?

The rough endoplasmic reticulum (RER), Golgi apparatus, and lysosomes are all organelles involved in the synthesis, modification, and processing of proteins and lipids in eukaryotic cells.

Here are some of the similarities they share:

1. Membrane-bound organelles: All three organelles are membrane-bound organelles, meaning they are surrounded by a membrane that separates their contents from the cytoplasm.
2. Involved in protein synthesis: The rough endoplasmic reticulum and the Golgi apparatus are involved in the synthesis, modification, and transport of proteins, while lysosomes are involved in the degradation of proteins.
3. Involved in protein modification: The Golgi apparatus and lysosomes are involved in further modifying proteins synthesized in the rough endoplasmic reticulum, adding or removing specific chemical groups such as sugars, phosphates, and sulfates.
4. Role in intracellular transport: All three organelles are involved in the transport of molecules within the cell. Proteins synthesized in the rough endoplasmic reticulum are transported to the Golgi apparatus for further processing and sorting, and from there they can be transported to lysosomes for degradation or the cell surface for secretion.
5. Important for maintaining cellular homeostasis: The rough endoplasmic reticulum, Golgi apparatus, and lysosomes all play important roles in maintaining cellular homeostasis. They ensure that proteins and lipids are properly synthesized, modified, and transported within the cell, and that waste materials are properly degraded.

Overall, the rough endoplasmic reticulum, Golgi apparatus, and lysosomes are interconnected organelles that work together to maintain cellular function and homeostasis in eukaryotic cells.

What does the golgi apparatus do in a plant cell?

The Golgi apparatus plays a critical role in the processing and sorting of proteins and lipids in plant cells. Here are some of the functions of the Golgi apparatus in plant cells:

1. Glycosylation: The Golgi apparatus is involved in glycosylation, which is the process of adding sugar molecules to proteins and lipids. This modification is essential for the proper function of many proteins, and it helps to determine the final destination of the proteins within the cell.
2. Sorting and processing of proteins: The Golgi apparatus is involved in sorting and processing proteins that are synthesized in the endoplasmic reticulum. It modifies these proteins by adding or removing specific chemical groups, such as sugars or phosphates, and packages them into vesicles for transport to their final destinations within the cell or outside of it.
3. Formation of cell wall components: The Golgi apparatus is also involved in the synthesis of cell wall components, such as cellulose and pectin. It modifies and packages these components for transport to the cell surface, where they are incorporated into the growing cell wall.
4. Secretion of materials: The Golgi apparatus is responsible for the secretion of materials such as hormones, enzymes, and other proteins. It packages these materials into vesicles and transports them to the cell surface, where they are released into the extracellular environment.

Overall, the Golgi apparatus plays a critical role in the processing and sorting of proteins and lipids in plant cells, and it is essential for the proper functioning of many cellular processes, including cell wall formation and secretion of materials.

What structures move proteins from the er to the golgi apparatus?

Proteins are transported from the endoplasmic reticulum (ER) to the Golgi apparatus via specialized transport vesicles. These vesicles bud off from the ER membrane and carry the proteins to the cis face of the Golgi apparatus.

The transport of proteins from the ER to the Golgi apparatus involves a series of complex cellular mechanisms. Here is a brief overview of the process:

1. Protein synthesis and processing in the ER: Proteins are synthesized by ribosomes on the rough endoplasmic reticulum (RER) and are modified and folded as they pass through the ER lumen.
2. Vesicle formation: Once the proteins are properly folded, they are packaged into specialized transport vesicles that bud off from the ER membrane. These vesicles are coated with protein complexes such as COPII, which help to select and sort cargo proteins for transport to the Golgi apparatus.
3. Vesicle fusion with the Golgi apparatus: The transport vesicles containing the cargo proteins move along the cytoskeleton to the cis face of the Golgi apparatus, where they fuse with the Golgi membrane and release their cargo.
4. Processing and sorting in the Golgi apparatus: The Golgi apparatus then processes and sorts the proteins further, adding or removing specific chemical groups such as sugars, phosphates, and sulfates. The proteins are then sorted into vesicles for transport to their final destinations within the cell or outside of it.

Overall, the transport of proteins from the ER to the Golgi apparatus is a highly coordinated process that involves the formation of specialized transport vesicles and their fusion with the Golgi membrane. These mechanisms ensure that proteins are properly processed and sorted, and that they reach their final destinations within the cell or outside of it.

MCQ on Golgi Apparatus

Which of the following is a function of the Golgi apparatus?
a) Protein synthesis
b) Lipid breakdown
c) Sorting and modification of proteins and lipids
d) DNA replication
Answer: c) Sorting and modification of proteins and lipids

Which of the following organelles is closely connected to the Golgi apparatus?
a) Mitochondria
b) Ribosomes
c) Endoplasmic reticulum
d) Peroxisomes
Answer: c) Endoplasmic reticulum

Which face of the Golgi apparatus is closest to the endoplasmic reticulum?
a) Cis face
b) Medial face
c) Trans face
d) Lysosomal face
Answer: a) Cis face

What is the appearance of the Golgi apparatus?
a) Spherical shape
b) Tubular shape
c) Stacked, flattened sacs
d) Random arrangement of membrane-bound vesicles
Answer: c) Stacked, flattened sacs

Which of the following processes involves the Golgi apparatus in plant cells?
a) Photosynthesis
b) Cell wall synthesis
c) Muscle contraction
d) Nerve impulse transmission
Answer: b) Cell wall synthesis

FAQ

References

1. Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. The Golgi Apparatus. Available from: https://www.ncbi.nlm.nih.gov/books/NBK9838/
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