1. ( T/F ) Peptide bond formation is catalyzed by multicomplex proteins of ribos
ID: 178841 • Letter: 1
Question
1. (T/F) Peptide bond formation is catalyzed by multicomplex proteins of ribosome.
2. (T/F) All the incoming tRNAs enter A site.
3. (T/F) Before ribosome binds to mRNA, the small and large subunits form a complex.
4. (T/F) ATP provides energy for several steps of translation.
TRANSLATION: Initiation A site Initiator tRNA P site Large 50s GTP subunit mRNA E site UGGAUA AUGGAU AM Add large subunit binding site Small 30S small 30s (RBS) subunit subunit Initiation complex TRANSLATION: Elongation Incoming E site tRNA mRNA recognition GTP P site A site A site P site Cycle continues three times P site A site GTP Peptide bond formation Translocation P site P site A site A siteExplanation / Answer
Ques-1. (T/F) Peptide bond formation is catalyzed by multicomplex proteins of ribosome.
Reason: True
Reason:
Protein synthesis: Normally an mRNA transcript is translated by ribosomes (rRNA) in one minute. The efficiency of the protein synthesis increases through “the process of translation” & is higher in both prokaryotes & eukaryotes due to “translation of single mRNA transcript by multiple ribosomes i.e. a string of polyribosomes are going to translate a single mRNA transcript in low time to produce same amount of protein.
Translation: Ribosomes (30S, 50S) considered as molecular machines and they synthesized from nuclear DNA to become smaller subunits and larger subunits in the cytoplasm. These subunits often converge each other to make mRNA translated for amino acid synthesis.
Protein synthesis occurs in three steps namely, initiation, elongation and termination. During initiation, the mRNA, tRNA comes together at the ribosome and the translation initiates at the start codon (AUG, codes for methionine). Initator tRNA is going to enter initially P site to code for methinone followed by entry of all tRNAs to A site.
During elongation, amino acids added to the growing polypeptide chain according to the mRNA sequence. The aminoacyl tRNA molecules are picked up by the elongation factors in the presence of GTP, Which enters the A site. On the ribosome, the mRNA codon bound at the A-site will be matched with appropriate anticodon of aminoacyl tRNA. The translational machinery plays a key role in this selection and proof reading.
After binding of correct codon and anti codon, the new amino acid is linked to the growing polypeptide chain in the P –site (peptidyl site) by a peptide bond. This process is catalyzed by an enzyme peptidyltransferase located at the peptidyl transferase center of the large ribosomal subunit (ribozyme, a multicomplex protein ribosome). A new peptidyl-tRNA now occupies the A site. The empty tRNA now moves to the E site and this process facilitated by another elongation factor (eEF 2) and GTP. The new peptidyl tRNA moves to the P site, and the cycle repeats until it reads a stop codon. The following picture depicts the various stages in elongation.
Translocation: It is the process of movement considerably 3 nucleotides over on the mRNA in order to enable further addition of other amino acids. Elongation factor -G-GTP is going to bind with tRNA in amino acyl site followed by hydrolysis and association with mRNA. Finally, tRNA in the amino acyl site to move to peptidyl site thereby amino acyl site is going to be free for another amino acyl-tRNA synthesis.
Ques-2. (T/F) All the incoming tRNAs enter A site --> false
Ques-3. (T/F) Before ribosome binds to mRNA, the small and large subunits form a complex ---> true
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