27 Questions
Which factor recognizes a termination codon and results in the release of the newly synthesized protein?
RF-3
What is the function of polyribosomes in a cell?
To make many copies of a polypeptide quickly
In prokaryotic translation, what is the function of formylated initiator tRNA?
Recognizes the start codon in mRNA
Which antibiotic blocks elongation by preventing aminoacyl-tRNA access to the A-site?
Tetracycline
What is the role of miRNA in inhibiting translation?
Facilitates mRNA degradation with perfect complementarity
What type of post-translational modification involves the formation of disulphide bridges?
Protein folding
What is the main function of zymogens or proenzymes?
Serve as inactive enzyme precursors activated within an organism
Which amino acid side chain does protein phosphorylation usually occur on?
Tyrosine
What is the main characteristic feature of polyribosomes?
They allow a number of ribosomes to translate a single mRNA simultaneously
What is the function of diphtheria toxin inactivation by ADP-ribosylation?
Catalyzing the transfer of ADP-ribose to host cells EF-2, inhibiting protein synthesis
What is the role of cycloheximide in eukaryotic cells?
Causing premature termination of translation in both prokaryotes and eukaryotes
Which organelle is responsible for the N-linked carbohydrate chains attachment to the amide nitrogen of Asn residue?
Endoplasmic Reticulum (ER)
What is the function of farnesyl group in the cell?
Targeting Ras protein to the cytosolic face of the plasma membrane
What is the clinical value of measuring C-peptide levels?
Indicating insulin production and secretion
Where does the maturation of insulin occur?
Golgi Apparatus
What is the role of signal sequence in protein translation?
Directing the polypeptide into the lumen of the rER
What is the function of the Shine-Dalgarno sequence in prokaryotic translation?
It ensures correct alignment of the start codon with the ribosome in prokaryotes.
What is the role of the elongation factor EF-Tu-GTP in prokaryotic translation?
It brings the appropriately charged tRNA to the codon in the empty A site during translation.
Which of the following statements is true regarding the initiator tRNA in prokaryotic translation?
It carries a formylated methionine for all codons in prokaryotes.
In prokaryotic translation, what is the function of the release factor (RF) during termination?
It allows peptidyl transferase to cleave ester bond between tRNA and the peptide.
What is the role of initiation factors (IFs) in prokaryotic translation?
They aid in the formation of the 30S initiation complex.
What distinguishes the Shine-Dalgarno sequence in prokaryotes from eukaryotic translation initiation in terms of ribosome binding?
Prokaryotes have a purine-rich Shine-Dalgarno sequence that binds to 16S rRNA, while eukaryotes lack this sequence and bind close to the cap at the 5' end.
Which statement accurately describes the role of EF-G-GTP during prokaryotic translation?
It catalyzes translocation of ribosome three nucleotides along the mRNA in the 3’ to 5’ direction.
'Charging' of tRNA involves:
Formation of an aminoacyl-adenylate and subsequent attachment of amino acid to tRNA.
'Formylation' of N-formylmethionine (fMet) carried by initiator tRNA signifies:
'Formylation' is required for recognition by small ribosomal subunit during initiation.
'Elongation factor EF-Tu-GTP' functions primarily to:
--Bring appropriate charged tRNA to codon in empty A site during elongation.
What distinguishes 'Initiator transfer RNAi' from 'Normal Met-tRNA'?
Initiator tRNA carries formylated methionine as first amino acid, whereas Normal Met-tRNA carries non-formylated methionine for all codons.
This quiz covers the termination phase of protein synthesis, where a termination codon is recognized by release factors, leading to the release of the synthesized protein. It also addresses the concept of polyribosomes, which allow for multiple ribosomes to simultaneously translate a single mRNA, leading to rapid polypeptide production.
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