Golgi body (Golgi apparatus or Golgi complex)- Properties, Structure, Functions

Golgi body Properties

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.

Structure of Golgi body

  • 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.
Golgi body (Golgi apparatus or Golgi complex)
Created with BioRender.com

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%

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