Golgi Apparatus

Golgi apparatus was discovered by Camillo Golgi, in the year 1950. It is also called a Golgi Complex or Golgi body, membrane-bound organelle of eukaryotic cells (cells with clearly defined nuclei) that is made up of a series of flattened, stacked pouches called cisternae. The Golgi apparatus is responsible for transporting, modifying, and packaging proteins and lipids into vesicles for delivery to targeted destinations. 

It is located in the cytoplasm next to the endoplasmic reticulum and near the cell nucleus. While many types of cell contain only one or several Golgi apparatus, plant cells can contain hundreds.

Golgi Bodies in Animal Cell

Animal cells tend to have fewer and larger golgi bodies. It is usually placed close to the nucleus and it receives protein from the endoplasmic reticulum and further transport it to the lysosome.

Golgi Bodies in Plant Cell

Plant cells tend to have more and smaller Golgi bodies. It serves the site at which the complex polysaccharides of the cell wall are synthesized. 

Golgi Apparatus Diagram

Below diagram show the structure of Golgi body:

It is made up of a series of flattened stacked pouches called cisternae.

[Image will be uploaded soon]

Structure of Golgi Apparatus

• Under the electron microscope, the Golgi apparatus is seen to be composed of stacks of flattened structures that contain numerous vesicles containing secretory granules.

• The Golgi apparatus is morphologically very similar in both plant and animal cells. However, it is extremely pleomorphic: in some cell types it appears compact and limited, in others spread out and reticular (net-like).

• Typically, however, Golgi apparatus appears as a complex array of interconnecting tubules, vesicles, cisternae.

 A. Cisternae

• It is the simplest unit of the Golgi apparatus is the cisterna.

• Cisternae (about 1 μm in diameter) are central, flattened, plate-like or saucer-like closed compartments that are held in parallel bundles or stacks one above the other.

• In each stack, cisternae are separated by a space of 20 to 30 nm which may contain rod-like elements or fibers.

B. Tubules

• A complex array of associated vesicles and anastomosing tubules (30 to 50 nm diameter) surround the dictyosome and radiate from it.

C. Vesicles

• The vesicles are further divided into three types:

1. Transitional vesicles  are small membrane limited vesicles which are thought to form as blebs from the transitional ER to migrate and converge to cis face of Golgi, where they work to form new stucture.

2. Secretory vesicles are varied-sized membrane-limited vesicles that discharge from margins of cisternae of Golgi. They, often, occur between the maturing face of Golgi and the plasma membrane.

3. Clathrin-coated vesicles  are spherical protuberances, about 50 μm in diameter and with a rough surface. They are found at the periphery of the organelle, usually at the ends of single tubules, and are morphologically quite distinct from the secretory vesicles.

Function Of Golgi Apparatus

Golgi apparatus performs various important function inside the cell like:

(i) The main function of Golgi apparatus is to carry out the processing of proteins generated in the endoplasmic reticulum. Golgi apparatus also transports protein to the different parts of the cell.

(ii) The Golgi enzymes present in membranous disks of cisternae carry out the modification of cargo proteins. Modification of various substances is carried out by enzymes in cisternae with the help of processes like phosphorylation and glycosylation.

(iii) To carry out the glycosylation and phosphorylation processes, nucleotide sugars are imported by the Golgi apparatus from cytosol.

(iv) Polysaccharides are attached with proteins in order to form caru) One of the tasks of Golgi apparatus is carrying out the breakdown of proteins and formation of small, active fragments.bohydrates.

(u) One of the tasks of Golgi apparatus is carrying out the breakdown of proteins and formation of small, active fragments.

(vi) Sulfate groups are added to protein molecules in the Golgi apparatus.

(vii) Incorporation of phosphate molecules onto molecules of proteins is also an important task carried out in the Golgi apparatus.

(viii) Transportation of lipids around cells and creation of lysosomes are the important functions carried out by Golgi apparatus.

(ix) Synthesis of proteoglycans is carried out by the Golgi body. The proteoglycans are found in extracellular matrices of animal cells.

(x) Carbohydrates are synthesized in the Golgi body. The process of carbohydrate synthesis involves production of polysaccharides and glycosaminoglycans (GAGs).

MCQ based on Golgi Bodies

1. Golgi apparatus in plant is known as:

1. Chloroplast

2. Leucoplast

3. Dictyosome

Answer: Dictyosome

2. Who discovered golgi apparatus:

1. Robert Hook

2. Robert Brown

3. Camillo Golgi    

 Answer: Camillo Golgi

3. Which organelle is known as traffic police of the cell:

1. Mitochondria 

2.  Lysosome

3.  Chloroplast

4.  Golgi apparatus

Answer: Golgi apparatus

4. Histochemical localisation of Golgi is by chemical staining with:

1. Bismarck red

2. Fast green

3. Osmium tetroxide 

Answer: Osmium tetroxide