Question 1

Which of the following statements best describes the role of aminoacyl-tRNA synthetases in protein synthesis?

Accepted Answer

They specifically attach amino acids to their corresponding tRNAs, ensuring the correct amino acid is added to the growing polypeptide chain.

Question 2

Which of the following is a unique feature of eukaryotic translation initiation compared to prokaryotic translation initiation?

Accepted Answer

Circularization of mRNA via interactions between the 5’ cap and the 3’ poly(A) tail.

Question 3

Which of the following antibiotics inhibits bacterial protein synthesis by binding to the A site and terminating translation?

Accepted Answer

Puromycin

Question 4

A mutation changes the third base of a codon from C to U. Which property of the genetic code allows the correct amino acid to still be incorporated?

Accepted Answer

The code is degenerate, allowing multiple codons to specify the same amino acid.

Question 5

Which of the following best explains why only a minimum of 32 tRNAs are required to translate all 61 sense codons?

Accepted Answer

The wobble hypothesis allows some tRNAs to pair with multiple codons due to flexible base pairing at the third codon position.

Question 6

Which of the following is true regarding the directionality of protein synthesis?

Accepted Answer

Proteins are synthesized from the amino terminus to the carboxyl terminus, and codons are read 5’ to 3’.

Question 7

Which of the following events occurs during the elongation phase of translation?

Accepted Answer

The ribosome moves one codon toward the 3’ end of mRNA, and the growing peptide is transferred to the amino acid on the tRNA in the A site.

Question 8

Which of the following statements about the Shine-Dalgarno sequence is correct?

Accepted Answer

It is a conserved sequence in prokaryotic mRNAs that aligns the ribosome with the start codon via base pairing with 16S rRNA.

Question 9

A patient is exposed to diphtheria toxin. Which step of protein synthesis is directly inhibited?

Accepted Answer

Elongation in eukaryotes due to inactivation of an elongation factor

Question 10

Which of the following best describes the chemical reaction that forms a peptide bond during translation?

Accepted Answer

A condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing water

Question 11

Which of the following is a consequence of the ribosome’s proofreading function during elongation?

Accepted Answer

Incorrectly bound tRNAs are rapidly dissociated, reducing errors in protein synthesis.

Question 12

Which of the following statements about the genetic code is FALSE?

Accepted Answer

The genetic code is ambiguous, so one codon can code for multiple amino acids.

Question 13

Which of the following best explains why aromatic amino acids are important in protein quantitation by spectroscopy?

Accepted Answer

They absorb light in the UV region, allowing detection and quantitation of proteins.

Question 14

Which of the following is a correct sequence of events during bacterial translation initiation?

Accepted Answer

Small subunit binds to Shine-Dalgarno sequence, initiator tRNA binds to P site, then large subunit associates.

Question 15

Which of the following best describes the function of release factors during translation?

Accepted Answer

They bind to stop codons in the A site, triggering hydrolysis of the polypeptide from the tRNA.

Question 16

A scientist is studying a new antibiotic that blocks the peptidyl transferase activity of the ribosome. Which step of translation will be directly affected?

Accepted Answer

Peptide bond formation during elongation

Question 17

Which of the following is a key difference between free and ER-bound ribosomes in eukaryotic cells?

Accepted Answer

ER-bound ribosomes synthesize proteins for the endomembrane system and secretion, while free ribosomes synthesize cytosolic proteins.

Question 18

Which of the following best describes the role of GTP hydrolysis during translation elongation?

Accepted Answer

It provides energy for the ribosome to move one codon along the mRNA during translocation.

Question 19

Which of the following statements about tRNA structure and function is correct?

Accepted Answer

The anticodon loop pairs with the codon on mRNA in an anti-parallel fashion.

Protein Translation and the Genetic Code: Biochemistry Study Notes

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