Friday, September 16, 2011

Ribosomes

We can describes Ribosomes as workbench of biosynthesis. in general ribosomes are complex ribonucleoproteins particles made up of two subunits & each subunits contains RNA & proteins.
Ribosomes has the ability to catalyze the peptide bonds in both eukaryote & prokaryotes by placing sites for placing mRNA, tRNA & mRNA-tRNA complementary. 

Ribosomes are made up of two subunits, large subunit & small subunit & each subunit composed of multiple proteins & one or more than one RNA


Ribosomes source
Monomer size
Subunit
Small
Large
Prokaryotes
70S
30S:       21 proteins
16S RNA
50S:
34 proteins
23S, 5S, RNA
Eukaryotes
80S
40S:
34 Proteins
18S RNA
60S:
50 proteins
28S, 5.8s, 5S RNA


you can notice in Prokaryotes, the ribosomes sedimentation is 70S, the whole ribosomes, the small subunits is 30S & the large subunit is 50S. some one may comes to his mined that 30S + 50S = 80S; SO why its 70S not 80S?
will the trick here that subunits are add by sedimentation not mathematically & this addition by sedimentation depends on the weight & mass.

Ribosomes are weighed in KD (kilodaltons). In Eukaryotes, 80S ribosomes are larger & more complex than prokarytoes. the 80S, the whole Ribosomes has a mass of 4200 KD, the small subunit 40S is 1400KD & the large subunit is 2800 KD


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