What is the role of ribosomes in protein synthesis in prokaryotes?

Question

I'm just abit confused. I understand that amino acids are formed, then i don;t know what else happens

I understand that Shine dalgarno sequence is important as it initiated the translation

Also then that tRNA is delivered to ribosomes.

I just need to know whats going on in a step by step process.

Answer 1

Protein synthesis is divided into two stages, Transcription and Translation.  In prokaryotes they happen nearly simultaneously.

Transcription:

1.  RNA Polymerase finds the promoter region of a gene and binds to it.

2.  RNA Polymerase builds a copy of the gene into mRNA.

Translation:

1. The ribosome binds to the mRNA at the Shine-Dalgarno squence.

2. The ribosome moves along the mRNA until it reaches a start codon (AUG).

3. A tRNA with an anticodon UAC (to match the AUG codon) brings the amino acid methionine to the ribosome.

4. The tRNA, and both subunits of the ribosome now assemble together on the mRNA at the start codon.  The tRNA is in the P site of the ribosome.

5. Another tRNA brings its amino acid into the the adjacent A site, matching its anticodon to the next codon (set of three nucleotides) on the mRNA.

6. Peptidyl transferase forms a peptide bond between the two amino acids and cleaves the methionine from its tRNA.

7. The first tRNA leaves and the ribosome slides down the mRNA so that now the second tRNA is in the P site.

8. A new tRNA brings its amino acid and docks into the A site.

9. Steps 6-8 repeat until the ribosome reaches a stop codon.  When a stop codon of the mRNA reaches the A site, there is no matching tRNA to enter, so the ribosome dissasembles, releasing the polypeptide.

To see an animation of this in eukaryotes, try: http://www-class.unl.edu/biochem/gp2/m_b...

Answer 2

Here you go, gov'nor!

http://www.biostudio.com/d_%20Protein%20...

http://en.wikipedia.org/wiki/Ribosome