Help With Protein Synthesis

Stcroix, ASN, PhD, RN · Sep 25, 2010

Ok here goes. DNA codes for all protein. When the need comes for a specific protein, the DNA double helix 'unzips' into two single strands. One of these strands acts as a template for Messenger RNA (mRNA), this process is know as transcription (think of it as sending a detailed message. This newly made mRNA is sent to the cytoplasm and travels to the ribosomes where it is used to code for amino acids that will be hooked together to build the needed protein. At the ribosomes, with mRNA as a template and the presence of amino acids, a new protein molecule is made...this process is called translation (think of it as 'translating' the instructions from the nucleus).

LorilouRN · Sep 26, 2010

Oh, I remember many an essay question on these! We had to remember the central dogma of molecular biology: DNA---->RNA----->Proteins (with transcription, aka RNA synthesis, occurring over the first arrow and translation, aka Protein synthesis, occurring over the second arrow). I always remembered transcription comes first like a medical transcriptionist having to decipher a doctor's verbal notes and then translation coming second, in that he or she has to turn doc's shortened notes into something everyone could read.

Steps in Transcription (as we learned them):

1. RNA polymerase recognizes something on the gene called the promotor sequence. This is basically your green light or start sign to this enzyme.

2. RNA polymerase breaks the hydrogen bonds of the DNA and adds the complimentary nucleotides to a template strand

3. This is complete when the polymerase reaches the termination sequence (like a stop sign). This results in one of 3 types of RNA: tRNA (for protein synthesis), rRNA (functional part of a ribosome) or a pre-mRNA (which goes through a maturation process in the cytoplasm of a cell and becomes mRNA.

(Here is a great animation!)

The pre-mRNA to mRNA process has two basic steps: exon splicing and adding the 5' cap and poly-A tail. In exon splicing the non coding parts of genes are called introns and are taken out by splicesomes. Exons then connect together. Then the 5'cap and poly-A tail are added to either end to prevent the mRNA from degrading in the cytoplasm.

(Here is a great animation!)

Once you have a mature mRNA, it will go through the steps of Translation:

1. Ribosome binds to the RBS (ribosomal binding site) on the mRNA

2. Ribosome moves to the start codon which is always AUG (adenine-uracil-guanine). The start codon is also sometimes called the initiator codon.

3. (Our prof explained the ribosome is like a couch with 3 cushions named E, P, and A and the tRNA comes to sit on the cushions). tRNA that carries amino acids with the complementary anticodon binds to the P site and then the next tRNA carrying another amino acid with the complementary anticodon to the next 3 binds to the A site.

4. The ribosome then moves along the mRNA and attaches the amino acids with peptide bonds to one another until it reaches the stop codon.

5. Chaperone proteins fold the polypeptide and then it's sent on to the Golgi apparatus for packaging.

(This animation is a great way to clarify what the above steps do. It was hard for me to understand just looking at it, especially when the amino acids start bonding until I watched this animation.)

Hope that helps a bit!

fleur-di-lis-RN2b · Sep 26, 2010

I'm in A&P I and I'm having trouble understanding protein synthesis, basically transcription and translation. Does anyone have a good web-site or explanation in lay-mans terms that might help me out? I will head to the tutor this week at school if I can't get a good grasp on it this weekend. (if I get can an appointment). Thanks to anyone who can help me out!:)

I had trouble with this at first, have you tried you tube for instructional videos? That helped me more than anything.

skybmonkey · Sep 26, 2010

This is an awesome 3rd animation of transcription and translation

http://www.vcbio.science.ru.nl/en/virtuallessons/cellcycle/trans/

http://www.hhmi.org/biointeractive/dna/animations.html

BSNMomOf6 · Sep 27, 2010

Thank you so much everyone! All this has helped me tons! My test is next week, hopefully if I keep reading/watching/reviewing it will all sink in b4 then. Thanks again wonderful people of Allnurses!

acedit · Jun 9, 2013

Hi guys! Does anyone have any other ideas for understanding protein synthesis? I've been going over and over it, but it's jut not clicking for me.

Thanks in advance!

ourgirls · Jun 9, 2013

If u still dont really understand, just study the power point