Functionasites of ribosomes By KK Sahu Sir

INTRODUCTION
HISTORY
STRUCTURE
70s PROKARYOTIC RIBOSOMES
80s EUKARYOTIC RIBOSOME
CHEMICAL COMPOSITION
FUNCTIONAL SITES OF RIBOSOME
OVER VIEW OF PROTINE SYNTHESIS
FUNCTION
CONCLUSION
REFERENCE
THANKYOU
Ribosomes (from ribonucleic acid and Greek-”soma” meaning body) are complexes of RNA and proteins that are found in all cells.
Ribosomes are of basically two types- 70S and 80S.
The S refers to the Svedberg unit. This is a sedimentation coefficient which shows how fast a cell organelle sediment in an ultracentrifuge. The heavier the structure more is its sedimentation coefficient.
Ribosomes are the sites of protein synthesis in both prokaryotes and eukaryotes.

1. FUNCTIONAL SITES OF RIBOSOMES By KAUSHAL KUMAR SAHU Assistant Professor (Ad Hoc) Department of Biotechnology Govt. Digvijay Autonomous P. G. College Raj-Nandgaon ( C. G. )

2. SYNOPSIS INTRODUCTION HISTORY STRUCTURE 70s PROKARYOTIC RIBOSOMES 80s EUKARYOTIC RIBOSOME CHEMICAL COMPOSITION FUNCTIONAL SITES OF RIBOSOME OVER VIEW OF PROTINE SYNTHESIS FUNCTION CONCLUSION REFERENCE THANKYOU

3. INTRODUCTION Ribosomes (from ribonucleic acid and Greek-”soma” meaning body) are complexes of RNA and proteins that are found in all cells. Ribosomes are of basically two types- 70S and 80S. The S refers to the Svedberg unit. This is a sedimentation coefficient which shows how fast a cell organelle sediment in an ultracentrifuge. The heavier the structure more is its sedimentation coefficient. Ribosomes are the sites of protein synthesis in both prokaryotes and eukaryotes.

4. HISTORY The electron microscope revealed the preasece of dense 150 to 200 angstrom substance, which was repported by PALADE in 1955. These granules may be found either in the free state eg - in the cell of the basal apidermal layers or attached to the out side of cytoplasmic membrane like the endoplasmic reticulum. Ribosomes are the extremely important structure in the cell. Ribosomes were first found in 1953 by Romanian cell biologist GEORGE PALADE as dense particales or granules for he was awarded Noble prize. The term “ ribosomes ” was proposed by scientist RICHARD B. ROBERTS in 1958.

5. STRUCTURE In all cells each ribosomes consists of a large and in the small subunit. The two subunits contain rRNA of different lengths as well as a different set of protein. The small ribosomal subunit contains a single rRNA molecules referred to as small rRNA . The large subunit contains a molecule of large rRNA and one molecules of 5s rRNA , plus an additional molecule of 5.8s rRNA in vertibrates . The lengh of the rRNA molecules ,the quantity of proteins in each subunit and the size of the subunit differ in bacterial and eukaryotes cell.

6. 70S RIBOSOME The small subunit of E. coli ribosomes consist of 16s rRNA and 21 proteins. The large subunit(50s) is composed of 23s and 5s rRNA and 31 protein. Each ribosomes contains one copy of the rRNA and one copy of each of the ribosomal proteins with one exception, one protein of 50s subunit is present in 4 copies .

7. 80s RIBOSOMES The subunit of eukaryotic ribosomes are larger and cantain more protein than prokaryotic. Small subunit 40s of eukaryotic ribosomes is composed of the 18s rRNA and approximately 33 protein. The large subunit 60s contains the 28s,5.8s and 5s rRNA and about 50 proteins .

8. RNA PROTEIN SUBUNITS ASSEMBLE RIBOSOME

9. CHEMICAL COMPOSITION A ribosome consists of a highly folded ribosomal RNA molecule and many attached protein and mg++. The mg++ ions help in binding subunits together. The proportion of ribosome RNA and protein is variable in bothtypes of ribosome. The RNA/protein ratio is 2:1 in the 70s ribosome while in the 80s ribosome it is 1:1 no lipids have been detected. The ribosome protein are basic and of many kind. Some are structrural other are enzymatic in function .

10. The enzyme peptidyle transeferase , which brings about the actual formation of the peptide bond is an integral part of the large subunit. The ribosome RNA is thought to be on the inside of the ribosome almost entirely covered by proteins. The ribosomes thus ribonucleoprotein particles(RNP). The ribosomal RNA forms about 80% of the total cellular RNA.

11. FUNCTIONAL SITES OF RIBOSOMES The riobosome has three tRNA binding sites. An aminoacyl - tRNA enters the A site. Peptidyl - tRNA IS bound in the P site. Deacylated tRNA exits via the E site. An amino acid is added to the polypeptide chain by transferring the poplypetide from peptidyl - t RNA in the P site to aminoacyl - tRNA in the A site.

12. The ribosomes has two sides for binding charge t-RNA

13. THE P AND A SITES POSITION THE TWO INTERACTING t-RNAs ACROSS BOTH RIBOSOME SUBUNITS

14. T-RNA INTERS THE A SITE

15. t-RNA and m-RNA move through the ribosome in the same direction

16. OVER VIEW OF PROTEIN SYNTHESIS

17. FUNCTION Ribosome called as “protein factories” of the cell because they take part in protein synthesis. The ribosome bound to the membranes synthesize protein for export as secretions by exocytosis.such cell include pancreatic cells ,liver cells chief cell in the gastric gland, mammary gland cells plasma cells etc. The free ribosome proeduce structure and enzymatic proteins for use in the cell itself. Such cells includes developing muscles cells skin cells erythroblasts. Eg - haemoglobin is an example of protein made by free ribosome in the young red blood corpuscles .

18. Two or more ribosomes simultaneously engaged in protein synthesis on the same m-RNA strand to form polyribosomes . Ribosomes also have protective function. The nascent polypeptiude chain passing through the tunnel or channel between the subunit are protected against the action of protein digesting enzymes. Ribosomes also furnish enzymes and factors needed for the formation of polypeptides. Ribosomes also provides for attachment of t-RNA’s and m-RNA which participate in protein synthesis .

19. CONCLUSION Thus we can say that ribosome is the most important cellular organella which take part in accomplish the life biggest aim, the expression of gene and perfome protective function by protecting nascent polypeptide chain from protein digestive enzyme and factor requried for peptide synthesis.

20. REFRENCE Molcular cell biology Lodish et. Al 6 th edition Gene 8 Benjamin lewin 8 th edition Cell bilogy P.K gupta Cell and molecular biology Gerald karp