TRNA Charging and Ribosomes – DNA, RNA and the Genetic Code

by Kevin Ahern, PhD

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    00:01 Okay, so if this is to work, it's essential then not only that that pairing occurs that I described, but it's also important that the transfer RNA have the right amino acid attached to it, because if the transfer RNA for a given anticodon has a random amino acid attached to it, then when that transfer RNA comes to the ribosome, a random amino acid would be incorporated and that wouldn't make any sense. Well it turns out that there's an enzyme that takes care of this and the enzyme that takes care of it is called an aminoacyl tRNA synthetase, and it works as follows. Here is a given transfer RNA that has a specific anti-codon sequence at the very bottom of it. In the mix of the cell, there are 20 different amino acids, the 20 different amino acids are shown schematically here as three, but in fact there are 20 that are there. The aminoacyl tRNA synthetase reads the anti-codon and then grabs the appropriate amino acid and attaches it to the three prime end.

    01:03 Now without this enzyme performing this function properly, the genetic code would have no meaning.

    01:09 It turns out that there's one aminoacyl tRNA synthetase for every distinct amino acid, meaning there's one for leucine, one for glycine, one for lysine, etc. There 20 of them. The structure where the translation process actually occurs is the ribosome and the ribosome has some very interesting structures. First of all it has two major subunits, what's called a large subunit and a small subunit and this is true whether we're talking about a prokaryotic cell or eukaryotic cell. On the left here we see the small subunit. In bacteria this called the 30S subunit, in eukaryotes it's called the 40S subunit because it's actually a little bit larger. The small subunit ribosome in bacteria contains the 16S ribosomal RNA that I've already described and it also contains 21 different proteins. The 50S ribosomal subunit is the larger subunit of the two and again in eukaryotes, it's called the 60S subunit because it's larger and the large subunit ribosome contains the 23S and the 5S ribosomal RNA's. The ribosomal RNA of large subunit also contains 31 different proteins.

    About the Lecture

    The lecture TRNA Charging and Ribosomes – DNA, RNA and the Genetic Code by Kevin Ahern, PhD is from the course Biochemistry: Basics.

    Included Quiz Questions

    1. Aminoacyl tRNA synthetase
    2. Ribozyme
    3. RNA polymerase
    4. Helicase
    5. Topoisomerase

    Author of lecture TRNA Charging and Ribosomes – DNA, RNA and the Genetic Code

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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