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RIBOSOMES

RIBOSOMES. Discovery of Ribosomes. Ribosomes first appeared under the electron microscope as dense granules. This discovery was made in the mid-1950s by Romanian cell biologist George Palade. Ribosome Synthesis.

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RIBOSOMES

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  1. RIBOSOMES

  2. Discovery of Ribosomes • Ribosomes first appeared under the electron microscope as dense granules. • This discovery was made in the mid-1950s by Romanian cell biologist George Palade.

  3. Ribosome Synthesis • Ribosomes are large ribonucleoproteins assembled from proteins and ribosomal RNA. • In eukaryotic cells the manufacturing of ribosomes takes place in the nucleolus. • Whereas in prokaryotes ribosomes are synthesised in the cytoplasm.

  4. Eukaryotic ribosomes are larger than 70S ribosomes. The ribosome consists of two subunits (a large and a small) constructing an 80S particle. The larger 60S subunit and the smaller 40S subunit. Eukaryotic Ribosomes

  5. Bacterial Ribosome • Bacterial ribosomes have an overall Svedberg unit of 70S. • Comprised of a large 50S subunit and a small 30S subunit.

  6. Image displaying translation taken from DNA: the secret of life Watson and Berry (2003) DNA: the secret of life.

  7. Translation • mRNA template associates with small sub-unit. • Ribosomes form peptide bonds between adjacent amino acids. • The growing polypeptide chain leaves the ribosome through an ‘exit tunnel’ in the body of the large subunit.

  8. Translation cont. • The reaction continues until the ribosome meets a STOP codon.

  9. References • Berg, J.M., Tymoczko, J.L., Stryer, L., 2006. Biochemistry. 6th Edition. New York: W.H. Freeman And Company. • Raven, P.H., Johnson, G.B, Mason, K.A, Losos, J., Singer, S., 2008. Biology. 8th edition. Boston:McGraw – Hill, Higher Education.

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