Golgi Body (Golgi Complex): Structure, Functions (original) (raw)
Golgi body or complex is an organelle that is bound by a membrane in eukaryotic cells.
The Golgi body is also called as Golgi apparatus, Golgi complex, lipochondrion, Barker’s body, Dalton Complex, and Apparato Reticulare.
Golgi complex may have distinct subunits called Golgiosomes, idiosomes, or dictyosomes.
It is called dictyosomes, in plants and lower invertebrates.
The flattened, stacked pouches known as cisternae are present in it.
The Golgi apparatus transports, modify and packs the proteins as well as lipids into vesicles.
Then, it delivers them to targeted places.
The Golgi body is situated in the cytoplasm which is next to the endoplasmic reticulum. Similarly, it is closer to the cell nucleus.
Different types of cells contain only one or more Golgi apparatus but plant cells can contain it abundantly which might be in hundred.
It is not found in prokaryotic cells. Examples: PPLO, bacteria, and blue-green algae.
It is found in all eukaryotic cells except:
- sieve tubes of plants
- sperms of bryophytes and pteridophytes
- red blood cell of animals
The Golgi body had been first seen by George (1867).
The Golgi body was observed in 1898 by Camillo Golgi in the nerve cells of owl and cat. He was a cytologist from Italy. It is named after him.
In Golgi’s early studies of nerve tissue, he had established a staining technique. He mentioned it as reazione near. It is called the black reaction. Nowadays, it’s said as the Golgi stain.
During this technique nerve tissue is fixed with potassium dichromate. It is then suffused with silver nitrate.
In the 1950s, when the microscope was started to use, the study and the presence of the Golgi body were confirmed.
In 1954 Dalton and Felix studied its structure under a microscope
The Golgi body is surrounded by an organelle-free cytoplasm called the zone of exclusion. It is also called a Golgi ground substance.
The shape and size of the Golgi body aren’t fixed.
They depend on the physiological condition of the cells.
Usually, the Golgi body is formed from four parts. They are:
- Cisternae
- Tubules
- Vesicles
- Vacuoles
a. Cisternae
- Generally, the Golgi body is formed from nearly four to eight cisternae.
- But in some single-celled organisms, it may contain as many as 60 cisternae.
- Matrix proteins hold the cisternae, and therefore the whole of the Golgi body is supported by cytoplasmic microtubules.
- Golgi apparatus consists of a stack of generally 4-8 membrane-bound saccules or cisternae.
- In fungi, unicisternal dictyosomes are present.
- The cisternae have a smooth membrane.
- But they are of variable thickness.
- They enclose the lumen.
- It contains a fluid which is also called a matrix.
- The thin layer of cytoplasm is present in the intercisternal space. It has parallel fibrils.
- Each cisterna is the functional unit of the Golgi complex.
- The margins of each cistern are frequently curved.
- The saccules are frequently curved to give a particular polarity to the Golgi body.
- One face of the apparatus is convex.
- The other face of the apparatus is concave.
- The convex side is present in the proximal end which is called forming face or cis-face.
- It is directed towards the nucleus.
- At this end, cisternae constantly receive vesicles (also called transitional vesicles) from the smooth endoplasmic reticulum.
- The concave side of the apparatus is called the maturing face (trans-face).
- The concave face or distal face cisternae is present towards the plasma membrane.
- The thickness of the maturing face is 7-8 nm.
- In the case of the forming face, they are about 4 nm in thickness.
- Their contents undergo various cisternae with the assistance of coated vesicles and intercisternal connectives.
- They ultimately reach the maturing face where they’re budded off as secretion, coated or Golgian vesicles, or vacuoles.
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b. Tubules
- They are short and branched.
- The tubules interconnect the various cisternae.
- They form a sophisticated network towards the periphery and maturing face of the apparatus.
- Tubules arise because of fenestrations of the cisternae.
- The diameter is generally 30-50 nm.
- They are mainly involved in the elaboration of secretory products.
c. Vesicles
- They are small sacs of 20-80 nm diameters that develop from tubules.
- The vesicles are found attached to the tips of tubules at various levels within the network.
- They’re of two types: Coated and smooth vesicles.
i. Coated vesicles
- The coated vesicles have a rough surface.
- Fine bristle-like outgrowths cover the coated vesicles.
- They bud off from the ends of peripheral tubules and pass into the cell membrane and helps in endocytosis.
- They elaborate membrane proteins.
ii. Smooth vesicles
- The smooth vesicles have a smooth surface.
- They contain secretory substances and are hence called secretory vesicles.
- They bud off from the tubules within the network.
- On being pinched off, they pass into the cell membrane and help in exocytosis.
d. Golgian vacuoles
- They are round vesicles or sacs which are enlarged parts of the cisternae.
- They became modified to make vacuoles.
- From the concave or maturing face of distal sacisternae, the vacuoles get developed.
- Golgian vacuoles contain amorphous or granular substances.
- Golgian vacuoles also function as lysosomes.
Functions of Golgi body
- The major role of the Golgi complex is secretion. It secrets gum, mucus, sweat, tears, saliva, etc.
- From the Endoplasmic reticulum proteins, pro-enzymes, lipids, steroids, and other substances pass to the Golgi complex.
- It may occur directly or through the agency of transitional vesicles.
- Golgi complex concentrates, modifies, and packages these bio-chemicals into the secretion vesicles.
- It later pinches off and passes out the secretory bio-chemicals through exocytosis or reverse pinocytosis.
- It helps in the transformation of one type of membrane into another type.
- It converts the membrane of the endoplasmic membrane into the selectively permeable plasma membrane, the differentiated membrane of the lysosome, etc.
- It also helps in recycling the cell membrane.
- In the plant cells, a cell plate is formed in the middle of the dividing cell. It happens when the vesicles get fused which is produced by the Golgi complex.
- Golgi complex stores, condense packs and transports various substances.
- The digestive enzyme obtained through the endoplasmic reticulum is stored by some of the vesicles or vacuoles of the Golgi complex.
- Vesicles of the Golgi complex forms the acrosome of sperms.
- It helps in the formation of the root hairs by their mother cells.
- The membrane of the vesicle of the Golgi complex helps the formation of plasma membrane after cytokinesis.
References for Golgi body
- Shakya M, Mehata KR, Gautam MK, Pokhrel KR and Khanal K (2020 ) “ Principles of Biology”, Asmita Books Publisher and Distributors Ltd, Bhotahity, Nepal
- https://www.biologydiscussion.com/cell/golgi-apparatus/golgi-apparatus-meaning-structure-and-functions/70510- 30%
- https://www.britannica.com/science/Golgi-apparatus- 12%
- https://answers.yahoo.com/question/index?qid=20110704122532AAXDskv– 1%
About Author
Sushmita Baniya completed her Master’s degree in Medical Microbiology from the National College of Science and Technology (NIST), Kathmandu, Nepal. She did her Bachelor’s degree in Microbiology from Birendra Multiple Campus, Chitwan, Nepal. She is interested in Genetics and Molecular Biology.