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Hi!

Do you think that you could send me exactly how protein synthesis works. I have a project due for Biology, and I don't quite get it. I would ask my teacher, but the way she explained it, I don't get it. Please help me. Thanks,  Tim

Hi Tim

Guess from your email address you are a Michael Jordan fan, eh?

To explain protein synthesis well enough, I may have to have you write me back and tell me what parts I did not say clearly. Sort of a conversation instead of me just writing it all down. So, please let me know what I need to explain better. But here goes the first try.

I am a baseball fan. Although I know something about basketball, I know more about baseball. Therefore, let me use an analogy between baseball and protein synthesis.

Some things that a cell does are simple enough for only one enzyme or maybe one enzyme after another to perform. For instance, when sugar enters the cell, one enzyme after another inside the cell attacks the sugar so that slowly the energy in the sugar is released to do work for the cell.

Other things that the cell does are complicated enough that it takes a 'team' of players to accomplish. Protein synthesis is one of these complicated tasks. In baseball your team would have a pitcher, a catcher, a shortstop, etc. In protein synthesis, your team has a ribosome, tRNA, mRNA, amino acids, and ATP as the source of energy to make the bonds that make the amino acids stick together in the protein chain. These players will play the craziest game of baseball you ever saw. The home team is always in the field, and the visiting team is always at bat. The aim of the game is to make a specific protein.

The ribosome is very complicated. It is almost like the baseball stadium where all the players play the game, except, it has a couple of players that live in the stadium. Kind of like the home team. The other team comes to the stadium where they all join in to make protein.

The ribosome is huge compared to the visiting team, just like the stadium is huge compared to the players. But the ribosome comes apart into two pieces. When mRNA shows up, the two ribosome pieces clamp down on the mRNA and become a whole ribosome. The mRNA will snake through the ribosome, like a shoestring being pulled through one eyelet of a shoe. Like a shoestring, the mRNA is thin, but very long compared to the ribosome. In our crazy baseball game, the mRNA is like the visiting team manager with a long, skinny list of the batting order.

Meanwhile, the tRNA and its amino acid are buddying up. They always play together. The tRNA just doesn't feel right with someone elses amino acid. The tRNA finds its correct buddy amino acid and then the duo shows up at the ribosome to play. Think of the tRNAs as the batters in our game and the amino acids as their own specific bats.

The manager mRNA is positioned on the ribosome so that just one name on the batting list is exposed at a time. Each name has three letters (a codon). Each tRNA batter recognizes his name and comes to the ribosome plate and physically sticks to his name on the batting list. The tRNA is carrying its own amino acid bat. The ribosome pitches. It pitches ATP. The tRNA swings and hits the ATP. But, in this crazy game of baseball, the ATP explodes and goes flying off as ADP and P. The energy released in the explosion causes the amino acid in the batting cage to stick to the last amino acid brought to the plate. The ribosome helps the stunned tRNA to let go of its amino acid bat. The tRNA roams out of the stadium to find another of its specific amino acid bats. The amino acid bat left behind in the batting cage is now attached to the amino acid bat chain (the growing protein chain) which is held on to by the ribosome until the game is over.

The ribosome moves the manager mRNA so that the next name on the batting list is exposed in the batting cage.

So, one by one, the batting order is fulfilled. And the result is a protein (amino acid chain) with the correct order of amino acids. At the end of the batting order, the game is over and the finished protein is released. The ribosome comes off the end of the mRNA, falls apart into two pieces and starts all over again when it finds a new mRNA.

In science language, this is what happened in our crazy baseball game: The two pieces of ribosome clamp on to a mRNA. The ribosome moves the mRNA through, one codon at a time. Meanwhile, each tRNA finds its correct amino acid. The tRNA-amino acid with the matching anti-codon attaches to the exposed codon. The ribosome uses the energy of ATP to make a covalent bond between the new amino acid and the growing protein chain. The ribosome then causes the tRNA to detach from the amino acid it was holding. The tRNA floats off and finds another of its matching amino acids. The ribosome moves the mRNA over to expose the next codon. Thus, one codon at a time is exposed and one amino acid at a time is connected to the growing protein chain. When the ribosome reaches the end of the mRNA, it falls off the mRNA and breaks back into two pieces. As it falls apart it releases the finished protein chain.

Whew!!!!

Like I said, please let me know what you get and what parts are still fuzzy. I am more than happy to help.

Thanks for a wonderful question.
Dr. Pat

Thanks a BUNCH!
Tim

I am trying to locate a list of species who have DNA that is most similar to humans, if you know where I can find out this information please forward it to me or if you will be sending it to me please include the species name and percentage of similarity.
Thank you for your assistance,
Drake

I do believe that the chimp is the closest to humans, as far as DNA sequence similarity is concerned. 98.5% of the DNA is identical in chimp and man. I am afraid I do not know of an exact resource for a list of DNA homology, although one is probably available. Hope this helps some.
Dr. Pat

 

 

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