Can someone describe protein synthesis please?

Question

In detail, but easy to understand:) thank you so much!! Best answer will be chosen quickly if you gave a good answer:)

Answer 1

Starting out with transcription, the RNA produced is used for production of polypeptide chain as shown...



Transcription :

1. INTITIATION : RNA polymerase binds to promoter region of DNA and initiates transcription process. As it moves along DNA unwinds and one of these 2 straands serve as DNA template for RNA synthesis. As a result complementary copy of RNA is constituted on template strand.



2. ELONGATION : Elongation of RNA chains takes place by means of core enzyme which move along with DNA template. After commencement of chain elongation singma factor of RNA polymerase dissociates from core enzyme and can be reused. RNA chain growth takes place in 5' -> 3' direction. It requires bivalent ion Mg2+ or Mn+.



3. TERMINATION : The mRNA thus separates from DNA template chain. It undergoes processing and passes into cytoplasm through pores in nuclear envelope. The spliy area of DNA forms hydrogen bonds and gets spirally coiled to assume the original form. It is accompained with Rho factor for succesful termination of RNA strand.



Synthesis of TRANSCRIPTION.

Sigma factor is weakly attached with other chains. The function of sigma subunit is to confer specify of RNA synthesis at promoter region. Once initiation begins, sigma facto gets dissociated. Rho factor helps in elongation and termination of RNA molecule.

Transcription in eukaryotes has to face exons and introns. Due to spicing, INTRONS are removed. Now exons are joined in a definite pattern. HnRNA shows 2 process :

> Capping : Here an unusual nucleotide [methyl guanosine triphosphate] is added to 5'- end of HnRNA.

> Tailing : Here adenylated residues are added at 3'- end in template independent manner. This type of fully processed HnRNA is called mRNA.



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TRANSLATION refers to process of polymerisation of amino acids from a polypeptide chain. The order and sequence of amino acids are defined by bases in the mRNA. The amino acids are joined by a bond known as peptide bond.

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Mechanism of TRANSLATION :

1. Activation of Amino acids : This reaction is brought about by binding of an amino acid with ATP. The step requires enzyme called amino acyl RNA synthetases.



2. Transfer of amino acid to tRNA : The amino acid is transfered to tRNA. As a result enzyme and ATP are liberated.



3. Initiation of Polypeptide chain :Charged tRNA shifts to ribosome. Ribosome consists of structural RNAs and so different proteins. The information for sequence of amino acid is present in sequence of bases of mRNA. Inititiation of polypeptide chain in prokaryotes is always brought about by amino acid methionine which is regularly coded by codon AUG.



[ NOTE : mRNA has some additional sequences tat are not translated and are referred as untranslated regions ( UTR ). The UTRs are present at both 5' and 3' ends. They are required for efficient translation process. ]



4. Elongation : During this, complexes composed of amino acid, linked to tRNA subsequently bind to appropriate codon in mRNA forming the complementary bases with tRNA anticodon. Ribosomes moves aling mRNA towards it 3'end . This shift of ribosome along mRNA is called translocation. Hydrolysis of GTP provides energy. This shift releases of tRNA which is empty.



5. Termination : The termination of polypeptide is signalled by one of the 3 terminal triplets in mRNA. There are UAG, UAA and UGA. At the time of termination , terminal codon immediately follows in last amino acid codon. After this, polypeptide chain, tRNA and mRNA are released. The subunits of ribosomes get dissociated.

Answer 2

DNA in the nucleus of cells is transcribed into pre-messenger RNA by RNA polymerase III, by creating a strand that is complementary to the template strand of DNA and contains the same message as the coding strand of DNA.

The pre-mRNA then undergoes post-transcriptional modification (although this process actually occurs while the RNA is transcribed). Through this process the mRNA is transformed into a mature mRNA transcript.

A 5'-cap is added to the 5' end of the RNA, which protects the 5' end from degradation by ribonucleases.

Introns (non-coding regions within the transcript) are spliced out, and the remaining exons are reconnected to form a single continuous molecule.

Polyadenylation of the 3' end occurs, in which about 200 Adenine units are added to the 3' end.



After processing has occured, the RNA moves out of the nucleus and attaches itself to a small subunit of a ribosome. (The small subunit recognises a sequence in the upstream region of the mRNA - the Shine-Dalgarno sequence to which it attaches and ensures the molecule is correctly positioned for translation to occur) The large subunit then attaches itself, and translation begins, adding one amino acid per codon. Termination of translation occurs due to a stop codon in the mRNA, for which there is no matching amino acid. The ribosome pauses and a release factor protein attaches itself in the site where amino acids usually attach and force the ribosome to dissociate and release the mRNA transcript and the polypeptide.

This polypeptide then moves through the endoplasmic reticulum and gains its secondary and tertiary structures. Some proteins will also interact with other proteins to form quaternary structures.

Answer 3

DNA transcribes its self as RNA and rna is sent of to the ribosomes. There it attaches its self to the ribosomes and tRNA transports amino acids that will complete RNA and make protein! :))

Answer 4

Refer this link:



http://classof1.com/homework_answers/biology/protein_synthesis/

Answer 5

i know amino acids are in there somewhere...