5. Cell Structure And Organization - part 07 - Golgi complex

 

5. Cell Structure And Organization - part 07 - Golgi complex


Golgi complex / Golgi apparatus / Golgi body:

  • It is  manufacturing cum packaging and transport unit of cell.
  • Golgi complex essentially consists of stacks of membranous sacs called cisternae.
  • Diameter of cisternae varies from 0.5 to 1 μm. 
  • A cell may have few to several cisternae depending on its function.
  • The thickness and molecular composition of two membranes of a Golgi sac differ from each other. 
  • The Golgi sacs show specific orientation in the cell. 
  • Each cisterna has a forming or ‘cis’ face (cis: on the same side) and maturing or ‘ trans’ face (trans: the opposite side).
  • Transport vesicles that pinch off from transitional ER merge with cis face of Golgi cisterna and add its contents into the lumen.
  • This explains why Golgi bodies are usually located near ER. 
  • Modified and condensed secretions leave Golgi through trans face again as membrane bound vesicles.
  • Golgi body carries out two types of functions - 
  1. modification of secretions of ER and 
  2. production of its own secretions.


  • Cisternae contain specific enzymes for specific functions. 
  • Refining of product takes place in an orderly manner. 
  • For example, glycolipids and glycoproteins that are brought from ER loose certain sugars and regain other, thus forming a variety of products.
  • Golgi bodies also manufacture their own products. 
  • Golgi bodies in many plant cells produce non-cellulose polysaccharides like pectin. 
  • Manufactured or modified, all products of Golgi complex leave cisternae from trans face as transport vesicles.

always remember :

  • The cisternae in Golgi body are not physically connected to each other as that are in ER.
  • According to recent studies it is proposed that cisternae of Golgi body themselves mature moving from cis to trans face. It is called ‘Cisternal maturation model’.
  • It is also said that some vesicles recycle their enzymes that have been carried forward by moving cisternae back to less mature region.
  • While they are leaving from the Golgi, certain markers may get impregnated on their membrane so that they can identify their specific target cell or cell organelle.

Comments

Post a Comment

Popular posts from this blog

6. Biomolecules - part 01 - Carbohydrates

Image
  6. Biomolecules - part 01 - Carbohydrates Introduction : Our planet is having a wide diversity of living organisms that are classified as - unicellular  (consisting of a single cell; including bacteria and yeast) or  multicellular  having many cells (e.g. plants and animals).  living organisms have cell as the basic structural and functional unit.  The cells have protoplasm containing numerous chemical molecules, the biomolecules. Biochemistry  : Biochemistry is  biological chemistry  that provides us the idea of the chemistry of living organisms and molecular basis for changes taking place in plants, animals and microbial cells.  It develops the foundation or understanding  all biological processes  and communication within and between cells as well as chemical basis of inheritance and diseases in animals and plants. Chemical analysis of all living organisms indicates presence of the most common elements like  carbon, h...
Read more

6. Biomolecules - part 02 - Lipids

Image
  6. Biomolecules - part 02 - Lipids B. Lipids : These are group of substances with greasy consistency with  long hydrocarbon chain containing carbon, hydrogen and oxygen. In lipids, hydrogen to oxygen ratio is  greater than 2:1  (in carbohydrates it is always 2:1). Lipid is a broader term used for fatty acids and their derivatives.  They are soluble in organic solvents (non-polar solvents).  Fatty acids are organic acids which are composed of hydrocarbon chain  ending in carboxyl group (-COOH).  They can be  saturated fatty acids  with no double bonds between the carbon atoms of the hydrocarbon chain.  Palmitic and stearic acids  found in all animal and plant fats are examples of saturated fatty acids. Unsaturated Fatty Acids  are with one or more double bonds between the carbon atoms of the hydrocarbon chain.  Oleic acid  found in nearly all fats and  linoleic acid  found in many seed oils are example...
Read more

6. Biomolecules - part 05 - Enzymes

Image
  6. Biomolecules - part 05 - Enzymes Enzymes : Thousands of different chemical reactions take place automatically at a given time in a tiny living cell. The reactions take place at the body temperature.  If these enzymes were not present in the cell, either the reactions would not occur or if they occur they would occur at a  very very slow rate . Know the scientists : German chemist  Edward Buchner  discovered enzymes by accident.  Buchner discovered that living cells were not necessary but that  yeast  extract could bring about fermentation.  He then coined the term Enzyme (Gk. En = in, zyma = yeast i.e. in yeast). This term is now commonly used for all biocatalysts. Each enzyme catalyzes a small number of reactions, specifically perhaps only one. Substrate :  The substance upon which an enzyme acts is termed as the substrate.  Endo-enzymes :  The enzymes which act within the cell in which they are synthesizedare known as en...
Read more