Polypeptide synthesis!

[intagurl]

Hey, guys, 🙂

I'm having trouble understanding the polypetide synthesis!👎
Do I actually need to know the detailed steps of the synthesis like
the P site and A site and the incoming aminoacyl-tRANA stuff?😱

If yes, can someone put them together in a simpler manner?
I confused!!!

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[Moni Ahmadian]

Inta girl,

I'm not sure to what extend you need to know the polypeptide synthesis, but here is summary of this process:

the mRNA exits the nuc of the cell in Eukaryotic cells. There are two types of ribosomes present: some are free in the cytosol some are sitting on the surface of the rough ER. The two subunits of the ribosomes attach. Ribosomes have three sites A, P, and E. The P is where the polypptide is being synthesized, E is the exit site of the trasfer RNAs, and A is where the amino acyl tRNAs come in.

To be continued 😀

Hey, guys, 🙂

I'm having trouble understanding the polypetide synthesis!👎
Do I actually need to know the detailed steps of the synthesis like
the P site and A site and the incoming aminoacyl-tRANA stuff?😱

If yes, can someone put them together in a simpler manner?
I confused!!!

 

[Moni Ahmadian]

Part II

a molecule of tRNA has 5 arms but you need to remember only two arms: the anti-codon arm and the amino acyl arm where the a.a.'s are attached. As you know a codon is just a three nucleotide secquence on the mRNA that code for a.a.'s. the anti codon arm of the tRNA recognize the codons of the mRNA and attachs the correct a.a. to the growing polypeptide chain. The starting codon for translation is AUG which codes for a.a. methionine (met). The translation stops at either of these codons UAA, UAG, UGA...

Hey, guys, 🙂

I'm having trouble understanding the polypetide synthesis!👎
Do I actually need to know the detailed steps of the synthesis like
the P site and A site and the incoming aminoacyl-tRANA stuff?😱

If yes, can someone put them together in a simpler manner?
I confused!!!

 

[Moni Ahmadian]

Part III

tRNA-met recognizes AUG codon and sits on the mRNA at the A position then it will be transfered to the P site when the next tRNA bearing the correct a.a. recognizes and sits at the A position. Now the amide linkage should be formed between the 2 available a.a.'s. It is very very important to remember that proteins are synthesized from the N-terminal to the c term. Then met is your N-term. So, the only way to create a bond is that the tRNA-met at the P location to tranfer its met to the tRNA-a.a. at A. The emptied tRNA is moved one step to the E site and is removed while the tRNA at the A site is moved one step to the P site awaiting the new tRNA come in. Again the P site tRNA trasfer its chain to the new tRNA at the A site and this process continues until we reach to the stop codons. So for example a new polypetide chain synthesized this way might be like this:

N terminal -Met- Leu-Arg-Asp-Ser-Val-C terminal

Hey, guys, 🙂

I'm having trouble understanding the polypetide synthesis!👎
Do I actually need to know the detailed steps of the synthesis like
the P site and A site and the incoming aminoacyl-tRANA stuff?😱

If yes, can someone put them together in a simpler manner?
I confused!!!

 

[Moni Ahmadian]

Part IV

As I said ribosomes are divided into two groups: free ribosomes flowing in the cytosol and non-free ribosomes attached to the Rough ER. Your polypeptide can be synthesized in both types. But, there will be a big difference in the proteins and enzymes functions and locations. those that are synthesized at the rough ER contain "signal peptides" at their end that directs the newly synthesized proteins to move into the ER for further modifications. Once they are modified they use into the vesicles and are transported to other organelles or to the plasma membrane and out of the cell. For example insulin is one of these types of proteins.

Those that are made by free ribosomes and destined to remain in the cytosol and carry out their functions there. So these will include the enzymes for the glycolysis that happen in the cytosol or the fatty acid synthesis.

So this was the summary of the translation process. I would say study that with pictures rather than memorizing from the kaplan book or other books.

Good luck

Hey, guys, 🙂

I'm having trouble understanding the polypetide synthesis!👎
Do I actually need to know the detailed steps of the synthesis like
the P site and A site and the incoming aminoacyl-tRANA stuff?😱

If yes, can someone put them together in a simpler manner?
I confused!!!

 

[intagurl]

wow, thanks, moni!
you are WONDERFUL!!!

 

[Moni Ahmadian]

don't mention it😉

wow, thanks, moni!
you are WONDERFUL!!!