Saturday, June 26, 2010

ribosomes 399 Louis J. Sheehan, Esquire

The system doesn’t allow me to attach the slides. Instead, I have numbered the slides and then listed the relevant slides.

1. Structure of ribosomes

More than 50 different proteins and several ribonucleic molecules are combined to comprise ribosomes. Ribosomes are composed of 1/3 protein and 2/3 RNA. RNA forms the core of the ribosome and proteins are found on the ribosomal surface. In eukaryotes, ribosomal subunits are constructed in the nucleus and are then exported to the cytoplasm where, when joined together, they catalyze the construction of and construct protein.

Prokaryotic and eukaryotic ribosomes are similar. In each case, they have (i) a small subunit and (ii) a large subunit. The two subunits are linked together on an mRNA molecule – typically near its 5’ end – when it is appropriate to initiate the synthesis of proteins. The small subunit is where the matching of the tRNAs and the codons of the mRNA takes place. The large subunit is where the polypeptide chain is constructed by bonding amino acids together. To translate the mRNA, the ribosome pulls the mRNA through its core.

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