30 Questions
What is the primary function of the A site in the ribosome?
To bind an aminoacyl-tRNA with a codon-anticodon match
During the three-step sequence of protein synthesis, what occurs in the second step?
A peptide bond forms between the amino acid on the A-site tRNA and the polypeptide on the P-site tRNA
What is the direction of amino acid addition during protein synthesis?
Amino acids are always added to the carboxyl end (C-terminus) of the polypeptide
What is the name of the site where tRNAs without amino acids exit the ribosome?
E site
How many phases does translation have?
Three phases
What is the role of the P site in the ribosome?
To hold the growing peptide chain
What occurs when the A site encounters a stop codon?
Termination of translation
What is unique about the initiator tRNA in eukaryotes?
It contains methionine
What is the function of a release factor?
To hydrolyze the bond linking the P-site tRNA to the polypeptide chain
What is a characteristic of ribosomes in both prokaryotes and eukaryotes?
They are ribozymes
What is the result of elongation?
Extension of the polypeptide chain
What is the difference in mRNA translation between prokaryotes and eukaryotes?
Prokaryotes translate polycistronic messages, while eukaryotes translate monocistronic messages
What is the role of aminoacyl-tRNA synthetases?
To catalyze the addition of amino acids to tRNAs
How many different tRNAs are there in most cells?
40
What is the function of the small subunit of the ribosome?
To hold the mRNA in place
What is wobble pairing, as proposed by Francis Crick?
A nonstandard base pairing at the anticodon's third position
What is the site where peptide bonds are formed during translation?
Peptidyltransferase site
How many tRNAs line up within the ribosome during translation?
3
What is the characteristic of translation in bacteria?
Transcription and translation occur simultaneously.
What is the main function of a polyribosome?
To translate mRNA into protein.
What is the role of the 3' end of tRNA?
It is the amino acid binding site.
What is the function of the loop at the opposite end of tRNA?
It contains the anticodon.
What is the purpose of aminoacyl-tRNA?
To transfer amino acids to the ribosome.
What is the difference between prokaryotic and eukaryotic translation?
Prokaryotes have simultaneous transcription and translation, while eukaryotes have separate transcription and translation steps.
What occurs at the start of the elongation phase of protein synthesis?
The initiator tRNA is in the P site and the E and A sites are empty
What is the function of elongation factors during protein synthesis?
To help move the ribosome during translocation
What is the net result of the three steps of translocation?
The ribosome moves forward on the mRNA, and the growing protein is transferred to the P site
What is the composition of the active site of the ribosome?
Entirely ribosomal RNA
What occurs during peptide bond formation?
The amino acid on the P-site tRNA is transferred to the amino acid on the A-site tRNA
What is the classification of the ribosome based on its active site?
Ribozyme
This quiz covers the process of translation elongation and termination, including the role of release factors and stop codons.
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