Week 9 Flashcards
Why is GTP hydrolysis required during translation initiation?
A) To provide energy for ribosomal subunit binding
B) To catalyze peptide bond formation
C) To remove introns from mRNA
D) To recruit aminoacyl-tRNA
To provide energy for the ribosomal subunit to bind
If a bacterial gene acquired a mutation in the ATG start codon,
which of the following processes would be affected?
A. Replication
B. Transcription
C. Translation
D. None of the above
E. All of the above
Translation
Codons only matter in mrna
Replication will not occur if there is a mutation in the pribnow box
What is the sequence of initiating translation
- Mrna binds to the 30s subunit, where the binding site is mediated by the shine dalgarno sequence
- Initiater trna/start trna binds
- Hydrolysis of GTP brings in the 50S subunit
Why does translation terminate at stop codons rather than at a specific protein sequence?
A) Stop codons signal ribosome dissociation via release factors
B) Stop codons have complementary tRNA molecules
C) Stop codons enhance ribosome recycling efficiency
D) Stop codons undergo modification by chaperone proteins
Stop codons signal ribosome dissociation via release factors
How does the role of elongation factors (EFs) in translation compare to initiation factors?
A) Both are required for peptide bond formation
B) Elongation factors aid in tRNA binding, while initiation factors assist ribosomal assembly
C) Initiation factors function after elongation is complete
D) Both types of factors regulate protein degradation
Elongation factors aid in tRNA binding, while initiation factors assist ribosomal assembly with mrna
How does the 23S rRNA of the ribosome contribute to translation during elongation transpeptidation?
A) Acts as a scaffold for ribosome assembly
B) Provides enzymatic peptidyl transferase activity for peptide bond formation
C) Recruits mRNA to the ribosome
D) Catalyzes ATP hydrolysis for translation initiation
It provides enzymatic peptidyl transferase activity for the charged trna and the empty trna to react, creating a pepetide bond in the A site
While energy to from peptide bonds come from ATP which is used to make amino acyl charged trna
*The peptidyl transferase reaction involves two substrate tRNAs, an aminoacyl-tRNA that binds to the ribosomal A site and a peptidyl tRNA that binds to the P site.
Why is the Shine-Dalgarno sequence critical for translation initiation in prokaryotes?
A) It recruits the ribosome to the correct start codon
B) It encodes the first amino acid in the protein
C) It provides energy for translation initiation
D) It signals the termination of translation
*recall the shine dalgarno sequence is only found in rna
It recruits the ribosome to the correct start codon
How do the Sec and Tat protein transport systems differ?
*recall sec and tat are secretion systems in bacteria that allow them to export stuff outside their membranes
Sec uses atp and transports unfolded proteins across the membrane, tec uses pmf and moves FOLDED proteins across the membrane
Describe how a peptide bond is formed suring transpeptidation
Amino acids in the A site performs a nucleophillic attack on the carboxyl group of the C terminal on the amino acid at the p-site
A type of trna that moves trna from the A site to the P site
Peptisyl trna
What is the evolutionary advantage of the Type III secretion system in pathogenic bacteria?
A) It allows direct injection of toxins into host cells
B) It enhances biofilm formation for nutrient absorption
C) It protects bacterial DNA from host immune attacks
D) It facilitates antibiotic resistance
It allows direct injection of toxins into host cells
Why are release factors necessary?
To finsih translation by:
- recognizing stop codons
Why is GTP hydrolysis required for translation termination?
A) It provides energy for the release factors to recognize stop codons and disassemble the ribosome
B) It catalyzes the final peptide bond formation before termination
C) It facilitates the addition of a special termination amino acid to the polypeptide
D) It modifies mRNA to prevent further translation
Provides energy for gtp for release factors to recognize stop codons and disassemble the ribosome into 30S and 50S subunits
How do chaperone proteins assist in protein folding?
`
They hydrolyze atp to stabilize folding
How does protein posttranslational modification influence protein function?
A) It alters protein activity, localization, and stability
B) It removes unnecessary exons from proteins
C) It decreases the protein’s ability to interact with other molecules
D) It prevents proteins from being degraded
Alters orotein fucntion, stability and localization
Proteins that aid the folding of nasent polypeptides and protect the cell form thermal damage
Molecular chaperones
Ptorins that helps transport proteins across the membrane
Molecular chaperones
Why would bacteria need to export proteins using secretion systems?
A) To enhance their ability to obtain nutrients, defend against competitors, or interact with host cells
B) To reduce excess protein accumulation inside the cell
C) To improve the speed of translation
D) To modify mRNA stability
To enhance their ability to obtain nutrients, defend against competitors, or interact with host cells
How does ribosome movement during elongation facilitate translation?
A) It ensures amino acids are correctly positioned for peptide bond formation
B) It prevents translation termination at premature sites
C) It allows the ribosome to skip unnecessary codons
D) It accelerates peptide bond formation
It ensures amino acids are correctly positioned for peptide bond formation
What is the key reason why tRNA must be charged before entering the ribosome?
A) To ensure the correct amino acid is delivered for protein synthesis
B) To prevent premature translation termination
C) To activate ribosome subunit binding
D) To assist in RNA splicing
To provide energy to trna to ensure the correct amino acid is delivered for protein synthesis
How do translation termination factors (release factors) function differently in prokaryotes and eukaryotes?
A) Prokaryotes have multiple release factors, while eukaryotes have only one
B) Prokaryotes do not require release factors for translation termination
C) Eukaryotic release factors catalyze ATP hydrolysis instead of GTP hydrolysis
D) Eukaryotic release factors are encoded by ribosomal RNA
A) Prokaryotes have multiple release factors, while eukaryotes have only one
Why is ATP hydrolysis often required for protein translocation and secretion?
A) To provide energy for movement across membranes
B) To degrade misfolded proteins before secretion
C) To activate ribosomal RNA for improved translation efficiency
D) To prevent proteins from folding too quickly
Provide energy to move proteins across the membrane
If the coding strand is:
5’ –
AGGAGGGTATGCTAATGTC*ACGCGTATGACAT
If the C position 19 (marked with *)were mutated to a G,
what kind of mutation would that be?
A. Missense mutation
B. Nonsense mutation
C. Silent mutation
D. Frameshift mutation
E. All of the above
Before mutation:
Coding strand: TCA
Mrna: UCA
Codes for ser
After mutation:
Coding sstrand: TGA
Mrna: UGA
Codes for stop codon
Therefore, the answer is a nonsense mutation
- a nonsense mutation is a genetic change where a codon that normally codes for an amino acid, suddenly codes for a stop codon
What would be the direct consequence of mutating the
Shine Dalgarno sequence so that it was non-functional?
A. RNA polymerase would not bind to the DNA
B. The mRNA would not be made
C. The mRNA would not bind to the 30S subunit
D. The initiator tRNA would not bind to the 30S subunit
E. The 50S subunit would not bind to the 30S subunit
The mrna would nt bind to the 30s subunit
The shine dalgarno sequence is crucial to help mrna bind to the 30S subunit or rna. It is not linked ti rna polymerase
Without EF-G, the tRNA with the growing polypeptide
would be stuck in the:
A. A site
B. P site
C. E site
D. None of the above because EF-G helps the first
amino acyl-tRNA bind to the ribosome
Solution: stuck in the A site
EF-G causes translocation (moving the trna from the A site to the P-site)
Which of the following post-translational modifications is not
involved in sensing and responding to ammonia concentration?
A. Uridylylation
B. Phosphorylation
C. Methylation
D. None of the above
Methylation
A is important for responding to ammonia limitations
B is important for responsid to amona limitations
D is incorrect
Which of the following processes would need
a type IV secretion system?
A. Conjugation
B. Transformation
C. Transduction
D. All of the above
Conjujation
*conjugation is direct cell to cell transfer of DNA
Transduction is a virus transferring its DNA in a host
Transformation is the reuptake of free dna in the environment
Why is it not possible for a Type IV secretion system to make
the Type IV pili that are involved in twitching motility?
A. Pilin subunits are found in the periplasmic face of the
plasma membrane, not secreted from the cytosol
B. Type IV pili are not secreted into another cell
C. Both A and B
D. Neither A nor B
C
Explanation:
Type IV pilli = secretes pili, DNA , protein
Tyoe IV pilli are only located in the periplasm and only stay in the periplasm
Type IV pili enable bacteria to attach to surfaces, move using “twitching motility,” and facilitate DNA uptake (transformation), playing key roles in adhesion, biofilm formation, and pathogenesis. 🚀
Tsr is a plasma membrane protein that starts an intracellular
signaling cascade when it encounters extracellular nutrients.
The most likely mechanism by which it does this is:
A. Activates chaperone proteins
B. Becomes post-translationally modified
C. Interacts with the Sec system
D. None of the above
Becomes post translationally modified
Reasons why the other choices are incorrect:
A- chaperone proteins help proteins fold under stress
C- sec system only secretes stuff out of the cell, it does not take things inward
For Tsr, a bacterial sensor, PTMs (like methylation) help it adjust how bacteria move toward food. So, PTMs help cells quickly react to changes by modifying proteins after they’re made—kind of like upgrading a phone with new features after buying it! 😊
Why are frameshift mutations often more harmful than point mutations?
A) They introduce stop codons that immediately halt protein synthesis.
B) They shift the reading frame, changing all downstream amino acids.
C) They only affect one amino acid, making them less impactful.
D) They only occur in non-coding regions, making them neutral.
They shift the reading frame, changing all downstream amino acids.
frameshift mutation: insertion of deletion of a nucleotide
point mutation: a mutation that chnages a single nucleotide which can be silent, missense, or nonsense
Biofilms are
A. A heterogeneous mixture of organisms
B. Attached to a solid surface
C. Comprised primarily of extracellular
polysaccharide
D. All of the above
all of the above
Is there extracellular DNA in a biofilm and if so, where does it come
from?
A. No, DNA is found inside of cells
B. No, DNA is released but then immediately degraded by nucleases
C. Yes, DNA is actively secreted from cells via Type IV pili
D. Yes, DNA is released from a small proportion of lysed cells
solution: yes, from small proportions of lysed cells
why are the other choices incorrect?
C: secretion systems are only for secreting DNA into a host cell
Why are drinks like Red Bull bad for your teeth?
A. They cause bacteria like Pseudomonas to undergo explosive death
B. They contain AHL, which stimulates biofilm growth
C. They facilitate the attachment of Streptococcus to tooth enamel
D. They help develop water channels in plaque, allowing for better
nutrient dispersal
They facilitate the attachment of Streptococcus to tooth enamel
redbull provides sugar for stretococcus, which increases lactic acid production, causing cavities.
redbull does not contain AHL
How do AHL and cyclic di-GMP regulate
biofilm formation?
A. They both bind to transcription factors
B. Only AHL binds to transcription factors
C. Only GMP binds to transcription factors
D. Neither binds to transcription factors
both AHL and GMP bind to transcription factors
When is AHL made?
A. When cell density is high
B. When cell density is low
C. All the time
D. When specific inducers are present
all the time. AHL is present when cell density is low or high
What is the benefit to using quorum sensing to regulate
gene expression?
A. The ability to attain a high concentration of AHL
B. Many bacteria can coordinate
C. High concentrations of cyclic-di-GMP contribute to
the production of poly-N-acetylglucosamine
D. All of the above
many bacteria can contribute. Quorum sensing is a cell to cell communication system that decides when a biofilm should be made based on population density
ability to attain high ahl and high concentrations are beneficial to create a biofilm, but it is not beneficial for regulating gene expression
how does quorem sensing regulate gene expression?
an increase of AHL triggers cyclic di GMP, and ci-di gymp binds to transcription factors, activating genes involved in biofilm formation
what is the difference between AHL and CDGMP in the context of biofilm synthesis?
AMP decides when biofilm synthesis should be made, CDGMP is what actually starts biofilm synthesis
