• Question: please explain protein synthesis

    Asked by 977nepk48 to Ed, Kerrianne, Nina, Oli, yoyehudi on 5 Nov 2017.
    • Photo: Kerrianne Harrington

      Kerrianne Harrington answered on 5 Nov 2017:

      This induces some anxiety and nervous sweating in me, as I haven’t studied biology since GCSE… That’s more years than I would like to admit! I kind of want to ask all the other physicists I work with this question, totally out of the blue, to see what their reactions are.

      Biology was also definitely not my best subject in science. Chemistry and Physics made sense to me, and if I forgot something, I could start with something else I remembered and work it out. I think I liked them more because there was more mathematics to them! But Biology always seemed like remembering a list of names and procedures. Revising this topic is definitely bringing back some of that feeling to me!

      My best attempt with some revision:
      Protein synthesis builds specific proteins. There are two steps:
      1. Transcription – ‘writing down’ the DNA. Corresponding genes are transcribed into RNA. There’s some processing and transport… then…
      2. Translation – outside the nucleus, the proteins are built using the code in the RNA.

      This is definitely a terrible, rusty physicists view of it. I am not the best person to explain this. It would probably be better to consult the helpful youtube videos I checked out:
      FuseSchool: https://www.youtube.com/watch?v=x5ZXQo-xeMo
      Khan Academy: https://www.khanacademy.org/partner-content/nova/rnawondermolecule/v/proteinsynthesis
      CrashCourse: https://www.youtube.com/watch?v=itsb2SqR-R0

    • Photo: Oli Wilson

      Oli Wilson answered on 6 Nov 2017:

      Ooh, this takes me back a year or two – just gone back to see if I had any good ways of explaining it when I was teaching (turns out I didn’t…). Basically, Kerrianne’s pretty much spot on!
      – In protein synthesis the DNA ladder unzips, and RNA letters (nucleotides) come in and match up to the section of code that’s being copied.
      – The one-stranded RNA section then wanders off and the DNA zips back up again. Because the single-stranded RNA molecule is much smaller than the DNA heffalump (not a technical term, do not use in exams, do not tell your teacher I’m a Scientist said it was ok), it can squeeze out of the nucleus.
      – The RNA makes its way over to tiny little protein factories called ribosomes in the cytoplasm. These read triplets of code in the RNA and bring in the amino acids that match the code.
      – These amino acids join up together and form big long chains, called polypeptides. If these chains are long and complicated enough, they’re also known as proteins. And boom, protein synthesised!
      In summary: DNA unzips, RNA copies code. RNA wanders off, DNA zips up. RNA to ribosome, code read, matching amino acids linked up –> polypeptide!

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