Thursday, November 20, 2008
I Need Analogies!
Just the other day I was sitting there listening to a microbiology lecture and this tiny but significant detail about the process of translation that I had always had trouble understanding finally became a little clearer. I was always a little shaky on my understanding of exactly how the tRNAs move within the ribosome and interact with (among other molecules) each other to form the polypeptide or protein (aspects of the process of translation). He (my professor) said it's like the tRNA in the P-site says to the one in the A-site, "Oh, I've been here awhile, I'm old and tired already, but you are young since you are newly arrived. So here take my load (the strand of amino acids which are attached to the tRNA in the P-site)." Then that 'old' tRNA is ejected from the ribosome. The 'old' tRNA "hands over" his polypeptide to the 'new' tRNA when a peptide bond is formed between its polypeptide chain and the amino acid on the 'new' tRNA. Then the old guy releases its bond to the polypeptide chain and is ejected from the ribosome. Next, the ribosome moves on down to the next codon on the mRNA, the tRNA in the A-site with its attached polypeptide strand moves over to the P-site and the whole process is repeated again and again. In this way more and more amino acids are added to the chain and a protein is synthesized. I know I should have understood this as a senior in my high school Biology class, but sometimes things just don't click until I hear somebody explain it in a particular way. It's like I have to be able to picture it happening in my mind because I'm a very visual learner like that. Maybe I have it all wrong, but right now this process makes sense to me, so I hope I learned it correctly.