Question

Describe the role of ribosomes in protein synthesis?

Answer 1

I'll describe the tRNA and ribosome roles in protein synthesis here.

Explanation:

I usually explain everything like this by using analogy, so if you need a more scientific explanation, I can also help (I studied RNA structure in graduate school :) ).

Simply stated, the ribosome is the enzyme that produces the peptide bond, and it does this over and over and over to produce many, many peptide bonds that result in a long polypeptide, that eventually folds into a protein. So ribosomes are the enzyme that produce proteins.

In this case, ribosomes are like a big 3D printer. In this 3D printer, you need two essential things! PLANS for making the cool stuff (mRNA) and the building material for making the stuff (tRNA...technically, charged tRNA....or AA-tRNA).

tRNA molecules are just like all the other RNA molecules (rRNA, siRNA, mRNA, tRNA, spliceosomal RNA, etc). What i mean by "same" is they are all made out of nucleotides `("ATP","GTP","UTP","CTP")`. They just have different roles in the cell.

So, tRNA have two major important parts - the `3'OH` end and the anticodon. The anticodon is a section of a stem-loop that is `3` nucleotides long, and it is basically the "identity" of the tRNA, or maybe like a barcode. The `3-OH` group is where an amino acid gets put on through an ester bond from the sugar to the `"AA"` carboxylic acid group. Anyways, the amino acid that gets put on corresponds to specific sequences in the anticodon. So you've got a bunch of tRNA - they have different amino acids on them with different anticodon loops, and they are your building blocks...they are your building material.

Now for the dance. The plans are on the mRNA, and they are kinda boring. Just `"AUGGUGCGCCGAGAU"`....on and on and on. This sequence comes from the DNA, but it gets its message sent to the 3D printer by way of the messenger RNA.

Ok, so the mRNA gets put on the floor and the 3D printer (ribosome) stands over a 3-nucleotide section of the mRNA: #"AUG GUG CGC" CGA GAU"#... and it stands over the `"AUG"`. These three nucleotide sections are called CODONS. Ribosome says, "ok, right, which of these tRNA fit with `"AUG"`..and the ribosome sees which of the ANTICODON sequences basepair with the mRNA CODON sequence...and when it finds it, it plucks off the Amino Acid. Then, it jumps to the next one and says, "Right, which one of the tRNA corresponds to `"GUG"` - it finds it, plucks off the amino acid and adds it to the first amino acid.

Now you've got a peptide bond...and as the ribosome continues down the mRNA, it adds more and more amino acids (that correspond to the CODONS...and eventually you get a polypeptide that gets folded into a protein.

Ok, I sort of skipped over the aminoacyl transfer reaction part, and the `"A"` site, `"P"` site and `"E"` site stuff in the ribosome, but the above is the general idea.