Cell Organelles Dicoverers

We have seen in the previous posts about all the organelles in an animal cell with their structure and functions. But have we wondered who discovered them? So, I just want to make it easy for you all by jotting down the organelles and their discoverers over here.

The Organelles of the Cell

1. Cell Membrane - Robert Hooke in 1665 first view the cells under the microscope and hence, he is credited with the discovery of cell membrane.
2. Centriole - Discovered by Edouard Van Beneden in 1883 and was described and coined by Theodor Boveri in 1888.
3. Centrosome - Discovered by Edouard Van Beneden in 1883 and was described and coined by Theodor Boveri in 1888.
4. Cytoskeleton - Nikolai K Koltsov in 1903 proposed that the shape of the cell is determined by the tubular network, the cytoskelton. However, the word was introduced and coined by Paul Wintrebert in 1931 (in French, cytosquelette).
   i. Microtubules - De Robertis and Franchi disovered microtubules in 1953 in nerve cell and later Sabatani, Bansch, Barnette in 1963 explained the structure of microtubule.
   ii. Microfilament/Actin Filaments - Edward David Korn discovered microfilament in 1968 in Acanthamoeba castellanii.
   iii. Intermediate Filaments - The groep of Howard Holtzer in 1968 discovered intermediate filaments.
5. Cytosol - Discovered in 1835and no single scientist can be accredited to its discovery.
6. Golgi Apparatus -Camillo Golgi identified it in 1897 and named after him in 1898.
7. Lysosomes - Discovered by Christian de Duve in 1949 (or 1950s).
8. Mitochondria - Albert von Kolliker studied mitochondria in muscle cell in 1857; Richard Altmann first recognized them as cell organelle in 1894; Term "mitochondria' coined by Carl Benda in 1898.
9. Nucleus - Robert Brown discovered cell nucleus in 1833.
10. Ribosomes -Discovered by George Palade in 1955.
11. Endoplasmic Reticulum - Albert Claude in Belgium and Keith Porter at Rockfeller Institue in 1945.
12. Vacuole - Antony van Leeuwenhoek is credited with discovery of vacuole when he was studying bacteria in 1676.
13. Plastids: 'Plastid' term was coined by Ernst Haeckel in 1866. however, in 1883, Andreas Schimper was the first to give the clear definition of plastid and he also explained the relationship between the different types. 
14. Nucleolus: The  nucleolus was first discovered in eel cells in 1774 by Felice Fontana.
15. Chromosomes: The chromosomes were first discovered by Karl Wilhelm von Nageli in 1842.

If any references are needed, feel free to contact me.!

Ribosomes - Protein Assemblers of the Cell

Ribosomes are tiny organelles which are present in large numbers in both prokaryotic and eukaryotic cells (described here). They are important site for protein synthesis.

Structure:

Structure of Prokaryotic Ribosome

The ribosomes are designated as per their rate of sedimentation as 70S for bacterial ribosomes and 80S for eukaryotic ribosomes (where S stands for rate of sedimentation).Both prokaryotic and eukaryotic ribosomes are composed of two different subunits. these subunits comprises of proteins and rRNAs. Both of the ribosomes have similar structure; however, they differ in some details like different number of proteins and types of rRNAs.

The prokaryotic 70S ribosome is made up of large subunit as 50S and small subunit as 30S.

The small subunit 30S consists of 21 proteins and 16S rRNA whereas the large subunit is consists of 34 proteins and 23S and 5S rRNAs.

Structure of Eukaryotic Ribosome

Eukaryotic 80S ribosomes in eukaryotes is made up of  60S as large subunit and 40S as small subunit. the large subunit, 60S is made up of 28S rRNA, 5.8S rRNA, 5S rRNA and approximately 45 proteins. Whereas the small subunit, 40S is comprises of 18S rRNA and approximately 30 proteins.

One of the striking feature of ribosome is that they can be formed in vitro by self assembly of their RNA and protein constituents. This was first described by Masayasu Nomura when he purified the constituents of ribosome and mixed them in appropriate conditions and the functional ribosome was re-formed.

Functions:

Translation of mRNA by a Ribosome into a Peptide Chain.

As already mentioned, the ribosome are the site for protein synthesis; which is the process of translating mRNA into proteins. The mRNA comprises a series of codons (triplets of nucleotides) that will ultimately form the amino acids to make the protein.
The ribosome uses this mRNA as template and translates each codon by pairing it with appropriate amino acid which is provided by aminoacyl-tRNA (aminoacyl-tRNA contains a complementary anti-codon). The ribosome contains three RNA binding sites as A, P and E. The A site binds an aminoacyl-tRNA; the P site binds a peptidyl-tRNA and E site binds a free tRNA before it exits the ribosome as can be seen in the diagram.