Protein Synthesis Quiz

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Questions and Answers

Which of the following is NOT a component required for protein synthesis?

Amino acids

Ribosomes

tRNA

DNA (correct)

What is the function of aminoacyl-tRNA synthetase?

It helps to elongate the polypeptide chain.

It catalyzes the attachment of an amino acid to its corresponding tRNA. (correct)

It helps to terminate the translation process.

It helps to initiate the translation process.

Which type of ribosome synthesizes proteins that are destined for secretion?

Free ribosomes

Membrane-bound ribosomes (correct)

Polysomes

All of the above

What is the role of tRNA in translation?

It carries amino acids to the ribosome. (D) Signup and view all the answers

What is a polysome?

A group of ribosomes translating a single mRNA molecule. (B) Signup and view all the answers

Which of the following is a characteristic of free ribosomes?

They synthesize proteins that remain in the cytosol. (C) Signup and view all the answers

Which of the following is NOT a post-translational modification of polypeptide chains?

Transcription (C) Signup and view all the answers

What is the role of ribosomes in translation?

They catalyze the formation of peptide bonds between amino acids. (D) Signup and view all the answers

In eukaryotes, what is the specific function of the 5' cap on mRNA during initiation?

The 5' cap interacts with initiation factors and assists in the binding of the 40S ribosomal subunit to the mRNA. (C) Signup and view all the answers

What is the difference in the initiation complex between prokaryotes and eukaryotes?

All of the above (D) Signup and view all the answers

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

It serves as a recognition site for the 30S ribosomal subunit, aligning the ribosome with the start codon. (C) Signup and view all the answers

Which of the following statements accurately describes the relationship between transcription and translation in prokaryotes?

Translation can start before transcription is completed. (C) Signup and view all the answers

Which molecule is directly responsible for carrying the first amino acid to the ribosome in the initiation complex?

tRNA (C) Signup and view all the answers

What is the role of GTP in the initiation process of translation?

Providing energy for the assembly of the initiation complex. (D) Signup and view all the answers

What is the function of initiation factors in translation?

They help assemble the initiation complex and promote the recruitment of the initiator tRNA. (D) Signup and view all the answers

What is the difference between the initiator tRNA in bacteria and in mitochondria?

Bacteria use a formylated methionine, while mitochondria use a regular methionine. (D) Signup and view all the answers

What role do aminoacyl-tRNA synthetases play in protein synthesis?

They covalently attach amino acids to specific tRNA molecules. (A) Signup and view all the answers

What is the function of the proofreading activity of aminoacyl-tRNA synthetases?

To remove incorrectly charged amino acids. (D) Signup and view all the answers

Which of the following components are essential for peptide synthesis?

Peptide elongation factors and energy sources like ATP and GTP. (B) Signup and view all the answers

What is released when ATP is cleaved during the aminoacylation process?

AMP and inorganic pyrophosphate. (C) Signup and view all the answers

Which molecule is recognized by aminoacyl-tRNA synthetases for the attachment of amino acids?

Uncharged tRNA. (B) Signup and view all the answers

How many amino acids require specific enzymes for attachment to tRNA?

<ol start="20"> <li>(C)</li> </ol> Signup and view all the answers

Which of the following correctly identifies the carrier of amino acids in protein synthesis?

tRNA. (C) Signup and view all the answers

What is released during the formation of aminoacyl-tRNA from the adenylated amino acid?

PPi and AMP. (B) Signup and view all the answers

What initiates the translocation process during protein synthesis?

GTP hydrolysis (A) Signup and view all the answers

Which site does the uncharged tRNA move to during translocation?

E site (D) Signup and view all the answers

What is the result of hydrolysis of the bond linking the peptide to tRNA during termination?

The nascent protein is released (C) Signup and view all the answers

When does protein synthesis terminate?

Upon reaching a stop codon (A) Signup and view all the answers

Which codons are recognized by release factors to induce termination?

Termination codons (A) Signup and view all the answers

What is the role of eIF-2 in the regulation of translation in eukaryotes?

Its phosphorylation leads to inactivation (A) Signup and view all the answers

Which site on the ribosome is exposed for the next amino acyl tRNA after translocation?

A site (B) Signup and view all the answers

What happens to mRNA and ribosomal subunits during the termination step?

They are released from the ribosome (B) Signup and view all the answers

What is the role of the initiator tRNA during the initiation of protein synthesis?

It carries a non-formylated methionine. (A) Signup and view all the answers

During elongation, what is the main role of elongation factors?

To assist in the binding of the correct aminoacyl-tRNA. (A) Signup and view all the answers

Which of the following statements accurately describes the three steps of elongation?

Translocation involves moving the ribosome from the 5′-end to the 3′-end. (D) Signup and view all the answers

How does the ribosome ensure that the correct amino acid is added during protein synthesis?

Using codon recognition by aminoacyl-tRNA. (A) Signup and view all the answers

Which component of the ribosome transfers the amino acid from the P site to the A site?

Peptidyl transferase. (A) Signup and view all the answers

What is the purpose of GTP hydrolysis during the elongation phase?

To facilitate the translocation of the ribosome. (A) Signup and view all the answers

What does each amino acid in a protein correspond to?

A codon. (B) Signup and view all the answers

Which of the following processes is NOT involved in the initiation of protein synthesis?

Elongation of the peptide chain. (C) Signup and view all the answers

Which of the following is an example of a protein modification that involves the addition of a carbohydrate chain?

Glycosylation (A) Signup and view all the answers

What is the primary function of a signal sequence in a newly synthesized polypeptide?

To direct the protein to its final destination within the cell (C) Signup and view all the answers

Which of the following is a key enzyme involved in the removal of signal sequences from proteins?

Peptidase (B) Signup and view all the answers

Which type of post-translational modification is often used to target proteins to lysosomes?

Glycosylation (A) Signup and view all the answers

What is the role of ubiquitin in protein degradation?

Ubiquitin attaches to proteins that are destined for rapid turnover, marking them for destruction by the proteasome. (D) Signup and view all the answers

Which of the following post-translational modifications primarily affects the activity of enzymes?

Phosphorylation (D) Signup and view all the answers

Which of the following post-translational modifications is most likely to occur in the endoplasmic reticulum?

Glycosylation (C), Hydroxylation (D) Signup and view all the answers

Which of the following is NOT involved in protein degradation?

Ribosome (B) Signup and view all the answers

Study Notes

Course Information

Course: BMS 141
Lecture Number: 10 & 11
Title: Translation
Instructor: Dr. Lamees Dawood
Program: Medicine and Surgery
Semester: Fall 2024
University: Galala University

Intended Learning Outcomes

List components required for translation
Outline the mechanism of translation
Explain initiation steps of prokaryotic protein synthesis
Explain elongation steps of prokaryotic protein synthesis
Explain termination steps of prokaryotic protein synthesis
Identify post-translational modifications of polypeptide chains

Translation Components

Amino acids: All 20 amino acids needed.
Ribosomes: Large complexes of protein and rRNA.
tRNA: At least one per amino acid, some have more.
- Prokaryotes typically use 70S ribosomes with subunits 30S and 50S, Eukaryotes use 80S ribosomes with subunits 40S and 60S
aminoacyl-tRNA synthetase: Enzymes to attach amino acids to tRNA.
Protein factors: Essential for initiation, elongation, and termination of protein synthesis
ATP & GTP: Energy sources for the process.
mRNA: Carries the genetic code.

Translation Process (Outline)

Initiation: mRNA binds to ribosome, initiation starts by binding to smaller subunit (30S in prokaryotes/40S in eukaryotes), followed by association of larger subunit (50S/60S) to form initiation complex.
- The initiation complex consists of two ribosomal subunits, mRNA, initiator tRNA (methionine in eukaryotes, formyl-methionine in prokaryotes), GTP, and initiation factors.
- Prokaryotes use IF-1, IF-2, and IF-3 as initiation factors; eukaryotes use over ten factors (eIFs). The 16S rRNA in Prokaryotic ribosomes recognizes the Shine-Dalgarno sequence in the mRNA. The 5' cap in eukaryotic mRNA is recognized by the ribosome and a complex of proteins, allowing translation to initiate.
Elongation: Adding amino acids to polypeptide chain
- Three steps:
  - Binding of an incoming aminoacyl-tRNA
  - Peptide bond formation (Peptidyl transferase)
  - Translocation
Termination: Stop codon enters A site. Release factors recognize the stop codon. The peptide is released from the ribosome. The ribosomal subunits and mRNA are separated.

Overview of Protein Synthesis

mRNA carries the code, ribosome is the site of protein synthesis, tRNA brings amino acids to the ribosome, according to mRNA codons.

Post-Translational Modifications

Protein targeting (localization signals/sequences)
Protein folding
Trimming (removal of portions of a protein)
Covalent modification (e.g., phosphorylation, glycosylation, hydroxylation)
Protein degradation, using ubiquitination and proteasome.

Additional Information

Multiple ribosomes can translate the same mRNA simultaneously (polysomes).
Translation in prokaryotes and eukaryotes has differences (e.g., initiation factors).

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Test your knowledge on the intricate processes of protein synthesis in this comprehensive quiz. Explore concepts from transcription to translation, the roles of ribosomes, tRNA, and more. Perfect for students in Biology 101!

Protein Synthesis Quiz - Biology 101

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