Ribosome Functional Domains and Assembly Quiz

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Questions and Answers

What is the function of the P-site in the ribosome large subunit?

Attachment of mRNA
Exit of empty tRNA
Binding of tRNA with amino acid
Binding of tRNA with peptide (correct)

Where are ribosomes found within a cell?

Golgi apparatus
Mitochondria
Cytosol (correct)
Nucleus

Where are ribosomal proteins synthesized?

Mitochondria
Endoplasmic reticulum
Cytosol (correct)
Nucleus

What is the function of the E site in the ribosome large subunit?

Exit of empty tRNA (A) Signup and view all the answers

Where are ribosome subunits assembled?

Nucleolus (C) Signup and view all the answers

What is the role of the small ribosome subunit during translation?

mRNA binding (C) Signup and view all the answers

Which antibiotic inhibits the transition from initiation complex to chain elongating ribosomes in prokaryotes?

Streptomycin (D) Signup and view all the answers

Which antibiotic blocks the peptidyl transferase activity in eukaryotes?

Cycloheximide (A) Signup and view all the answers

What is the mechanism of action of the antibiotic puromycin?

Causes early termination of translation (D) Signup and view all the answers

Which toxin irreversibly inhibits the peptidyl transferase activity in eukaryotes?

Ricin (C) Signup and view all the answers

What is the function of ubiquitin in the proteasome system?

It marks proteins for degradation by the proteasome (C) Signup and view all the answers

Where are proteasomes located in eukaryotic cells?

In both the cytosol and the nucleus (B) Signup and view all the answers

What is the role of aminoacyl-tRNA synthetases in protein synthesis?

They catalyze the formation of aminoacyl-tRNA molecules by attaching amino acids to their corresponding tRNAs. (B) Signup and view all the answers

Which of the following statements about translation initiation is correct?

Translation initiation occurs in the cytosol for all proteins, regardless of their final destination. (A) Signup and view all the answers

What is the primary function of translation termination factors?

To recognize stop codons and promote the release of the polypeptide chain and the mRNA from ribosomes. (B) Signup and view all the answers

Which of the following statements about translation elongation is correct?

Elongation factors help aminoacyl-tRNAs bind correctly to the ribosome for polypeptide chain elongation. (C) Signup and view all the answers

Which of the following statements about the stages of translation is correct?

The three stages of translation are initiation, elongation, and termination, in that order. (B) Signup and view all the answers

What is the difference between initiation factors and elongation factors in the process of translation?

Initiation factors promote the proper association of ribosomes with mRNA, while elongation factors recognize stop codons and release the polypeptide chain. (C) Signup and view all the answers

What is the primary role of the Kozak consensus sequence in eukaryotic translation initiation?

It facilitates recognition of the start codon (AUG) by the ribosome. (A) Signup and view all the answers

Which of the following statements about eukaryotic translation initiation is correct?

At least one initiation factor aids in recognizing the 5' cap of mRNA. (D) Signup and view all the answers

What is the primary function of the Shine-Dalgarno sequence in prokaryotic translation initiation?

It aids in the binding of the initiator tRNA to the small ribosomal subunit. (C) Signup and view all the answers

Which of the following events occurs after the correct base pairing between the anticodon of the initiator tRNA and the start codon in prokaryotic translation initiation?

The hydrolysis of GTP by the initiation factor IF2. (B) Signup and view all the answers

In eukaryotic translation initiation, what is the primary role of the 5' untranslated region (5' UTR) of mRNA?

It is not translated and serves as a binding site for initiation factors. (B) Signup and view all the answers

Which of the following statements accurately describes the role of initiation factors in prokaryotic translation initiation?

GTP-bound IF2 aids in the recognition of the initiator tRNA by the small ribosomal subunit. (A) Signup and view all the answers

After the completed polypeptide is released from the ribosome, what happens next in the translation process?

The tRNA is discharged, and the mRNA and ribosomal subunits dissociate, allowing for a new translation cycle to begin. (A) Signup and view all the answers

In eukaryotes, what facilitates the reassociation of the ribosome subunits at the 5' end and the initiation of a new translation cycle?

The circular structure formed by the mRNA, allowing the 5' and 3' ends to associate. (C) Signup and view all the answers

What is the significance of polysomes or polyribosomes in the translation process?

They enable the translation of a single mRNA molecule by multiple ribosomes, significantly speeding up the rate of protein synthesis. (D) Signup and view all the answers

In eukaryotes, how does the presence of circular polysomes contribute to the efficiency of translation?

It allows for the rapid recycling of ribosomal subunits, as they can readily find the nearby 5' cap (m7G) and initiate another round of synthesis. (A) Signup and view all the answers

Which statement about the function of ribosomes in polysomes is correct?

Each ribosome in a polysome functions independently and synthesizes a separate polypeptide chain. (C) Signup and view all the answers

What is the primary advantage of having polysomes or polyribosomes in the translation process?

It significantly speeds up the overall rate of protein synthesis, making the process more efficient. (B) Signup and view all the answers

Flashcards

P-site function

Binds tRNA carrying the growing polypeptide chain.

Ribosome location

Cytosol (in both prokaryotes and eukaryotes).