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Questions and Answers
What is the primary function of the ribosome-binding sequence in bacterial mRNA?
What is the primary function of the ribosome-binding sequence in bacterial mRNA?
- To ensure the correct orientation of the mRNA on the ribosome, placing the start codon in the P site (correct)
- To specify the amino acid sequence of the protein to be translated
- To signal the start of the gene and initiate transcription by RNA polymerase
- To prevent the mRNA from being degraded by cellular enzymes before translation can begin
Antibiotics that specifically target bacterial ribosomes are effective because they:
Antibiotics that specifically target bacterial ribosomes are effective because they:
- Interfere with the binding of the initiator tRNA to the start codon
- Inhibit the formation of peptide bonds between amino acids
- Prevent the proper assembly of the ribosome subunits
- All of the above (correct)
Which of the following is NOT a characteristic of the initiation of protein synthesis in bacteria?
Which of the following is NOT a characteristic of the initiation of protein synthesis in bacteria?
- A single mRNA can be translated by multiple ribosomes simultaneously, resulting in polyribosomes
- Initiation requires a specific mRNA sequence, known as the Shine-Dalgarno sequence, for ribosome binding
- The large ribosomal subunit joins the complex, bringing the catalytic site required for peptide bond formation
- Initiator tRNA binds to the P site of the ribosome, carrying the amino acid fMet (correct)
Why are antibiotics that target bacterial ribosomes generally considered safe for human use?
Why are antibiotics that target bacterial ribosomes generally considered safe for human use?
What is the significance of a polycistronic mRNA in bacteria?
What is the significance of a polycistronic mRNA in bacteria?
Which of the following antibiotics specifically inhibits RNA synthesis in bacteria?
Which of the following antibiotics specifically inhibits RNA synthesis in bacteria?
Which antibiotic works by inhibiting translation in bacterial ribosomes?
Which antibiotic works by inhibiting translation in bacterial ribosomes?
Which of these is a common target for antibiotics that inhibit bacterial protein synthesis?
Which of these is a common target for antibiotics that inhibit bacterial protein synthesis?
How do antibiotics that inhibit bacterial protein synthesis exert their effects?
How do antibiotics that inhibit bacterial protein synthesis exert their effects?
Why can these antibiotics specifically target bacterial protein synthesis without harming the host?
Why can these antibiotics specifically target bacterial protein synthesis without harming the host?
What is the mode of action of streptomycin in inhibiting bacterial protein synthesis?
What is the mode of action of streptomycin in inhibiting bacterial protein synthesis?
Which of the following is NOT an antibiotic that inhibits bacterial protein synthesis?
Which of the following is NOT an antibiotic that inhibits bacterial protein synthesis?
What is a key reason why antibiotics targeting bacterial protein synthesis are often effective?
What is a key reason why antibiotics targeting bacterial protein synthesis are often effective?
What is the primary function of ribosomal proteins in the ribosome?
What is the primary function of ribosomal proteins in the ribosome?
How does the ribosome ensure that protein synthesis begins at the correct start codon?
How does the ribosome ensure that protein synthesis begins at the correct start codon?
Which of the following is a true statement about the speed of protein synthesis in prokaryotes and eukaryotes?
Which of the following is a true statement about the speed of protein synthesis in prokaryotes and eukaryotes?
Which of the following antibiotics would be most effective at inhibiting protein synthesis in bacteria without affecting eukaryotic cells?
Which of the following antibiotics would be most effective at inhibiting protein synthesis in bacteria without affecting eukaryotic cells?
What is the significance of the initiator tRNA in the process of protein synthesis?
What is the significance of the initiator tRNA in the process of protein synthesis?
Which one of the following antibiotics is known to selectively inhibit bacterial protein synthesis by preventing the attachment of tRNA to the ribosome?
Which one of the following antibiotics is known to selectively inhibit bacterial protein synthesis by preventing the attachment of tRNA to the ribosome?
How do antibiotics like streptomycin interfere with bacterial protein synthesis?
How do antibiotics like streptomycin interfere with bacterial protein synthesis?
Which of the following antibiotics inhibits bacterial protein synthesis by blocking the formation of peptide bonds?
Which of the following antibiotics inhibits bacterial protein synthesis by blocking the formation of peptide bonds?
Which antibiotic specifically targets bacterial RNA polymerase, thus preventing the synthesis of bacterial mRNA?
Which antibiotic specifically targets bacterial RNA polymerase, thus preventing the synthesis of bacterial mRNA?
Flashcards
Initiator tRNA
Initiator tRNA
The first tRNA that binds to the start codon AUG during protein synthesis.
P site
P site
The location on the ribosome where the initiator tRNA binds during the start of protein synthesis.
Ribosome-binding sequence
Ribosome-binding sequence
A short sequence in bacterial mRNA that helps ribosomes attach, located before the AUG codon.
Polycistronic mRNA
Polycistronic mRNA
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Start codon
Start codon
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Polyribosomes
Polyribosomes
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Translation Duration
Translation Duration
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Antibiotics
Antibiotics
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Ribosomal Differences
Ribosomal Differences
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Proteases
Proteases
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Protein Lifespan
Protein Lifespan
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Protein Regulation
Protein Regulation
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Misfolded Proteins
Misfolded Proteins
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Ribosome
Ribosome
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rRNA
rRNA
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Peptidyl transferase
Peptidyl transferase
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mRNA
mRNA
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Translation initiation
Translation initiation
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AUG codon
AUG codon
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Eukaryotic ribosome efficiency
Eukaryotic ribosome efficiency
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Study Notes
Introduction to Molecular Biology Lecture 6
- The lecture covers the process of protein synthesis from mRNA.
- Key topics include the genetic code, charged transfer RNAs (tRNAs), ribosomes, translation initiation/termination, and relevant concepts like antibiotics, proteasomes, and post-translational modifications (PTMs).
Genetic Code
- mRNA sequence is decoded in sets of three nucleotides (codons).
- Four different nucleotides code for 20 different amino acids (AAs) in proteins.
- The set of rules for translating a gene's nucleotide sequence into the amino acid sequence of a protein is known as the genetic code.
- Codons consist of three nucleotides, giving 64 possible codons.
- Most amino acids are coded by more than one codon.
- Three codons are stop codons, signifying the termination of protein synthesis.
- One codon, AUG, acts as the initiation codon, specifying methionine (Met).
Transfer RNAs (tRNAs)
- tRNAs are adaptor molecules that match amino acids to codons on mRNA.
- Each tRNA is approximately 80 nucleotides long and has a cloverleaf structure.
- The structure includes an anticodon region that base-pairs with the complementary codon in the mRNA.
- A short, single-stranded region at the 3' end covalently binds the specific amino acid.
Ribosomes
- Ribosomes are large complexes composed of ribosomal proteins and ribosomal RNA (rRNA).
- Bacterial and eukaryotic ribosomes are similar in structure and function.
- Each ribosome is a ribozyme, possessing a catalytic site for peptide bond formation.
- Ribosomes have three binding sites for transfer RNAs: A site (aminoacyl-tRNA), P site (peptidyl-tRNA), and E site (exit).
Translation
- Translation occurs in a four-step cycle.
- The mRNA is translated in a 5' to 3' direction.
- The N-terminus of the protein is made first; subsequent amino acids are added to the C-terminus.
Protein Synthesis in Bacteria
- Bacterial mRNA molecules contain ribosome-binding sequence that is located upstream from the start codon (AUG).
- Bacterial ribosomes can bind directly to the start codon.
Termination of Translation
- Translation ends when a stop codon is reached.
- Stop codons are not recognised by tRNAs and do not code for an amino acid.
- Proteins known as release factors bind to the stop codon in the ribosome's A site to halt translation.
- The polypeptide chain is released.
Protein Breakdown
- Proteases are enzymes that degrade proteins, hydrolysing peptide bonds between amino acids.
- Proteins have varying lifespans, from months to seconds.
- Proteasomes are large protein machines responsible for protein degradation. They are present in both cytosol and nucleus..
- In eukaryotes, proteins destined for degradation are often tagged with ubiquitin, which targets them to proteasomes.
Post-translational Modifications (PTMs)
- Many proteins undergo PTMs after translation to become fully functional.
- PTMs include covalent modifications like phosphorylation and glycosylation.
Additional Notes
- The lecture also touches upon the concept of polyribosomes (polysomes).
- Various antibiotics that target bacterial protein synthesis are also discussed.
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Description
This quiz covers key concepts from Lecture 6 of Introduction to Molecular Biology, focusing on the process of protein synthesis from mRNA. Explore essential topics such as the genetic code, the role of tRNAs, ribosomes, and the mechanisms of translation initiation and termination.
