This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Protein Synthesis”.
1. Bacteria have ____________
a) 70S ribosomes
b) 60S ribosomes
c) 50S ribosomes
d) 80S ribosomes
View Answer
Explanation: Bacteria have 70S ribosomes, with a large (50S) and a small (30S) subunit.
2. Which of the following inactivates the 60S subunit of eukaryotic ribosomes?
a) Chloramphenicol
b) Cycloheximide
c) Diphtheria toxin
d) Ricin
View Answer
Explanation: Ricin inactivates the 60S subunit of eukaryotic ribosomes by depurinating a specific adenosine in 23S r-RNA.
3. Which is the third elongation step in bacteria?
a) Peptide bond formation
b) Binding of an incoming aminoacyl t-RNA
c) Translocation
d) None of the mentioned
View Answer
Explanation: Binding of an incoming aminoacyl t-RNA is the first step, peptide bond formation
is the second step and translocation is the final elongation step in bacteria.
4. In how many steps protein biosynthesis takes place?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: Activation of amino acids, initiation, elongation, termination and release and folding and posttranslational processing are the five steps.
5. What is the role of mRNA in protein synthesis?
a) It translates genetic code to a specific amino acid
b) It modifies mRNA molecules prior to protein synthesis
c) It provides a genetic blueprint for the protein
d) It catalyzes the process
View Answer
Explanation: t-RNA translates genetic code to a specific amino acid.
sn-RNA modifies mRNA molecules prior to protein synthesis.
r-RNA catalyzes the process.
6. What is the role of small nuclear RNAs in protein synthesis?
a) It translates genetic code to a specific amino acid
b) It modifies mRNA molecules prior to protein synthesis
c) It provides a genetic blueprint for the protein
d) It catalyzes the process
View Answer
Explanation: t-RNA translates genetic code to a specific amino acid.
r-RNA catalyzes the process.
mRNA provides a genetic blueprint for the protein.
7. The eukaryotic mRNA binding to the ribosomes is facilitated by ____________
a) T-RNA
b) Poly-A tail
c) Shine Dalgarno sequence
d) 7-methyl guanosine cap
View Answer
Explanation: The initiating (5’) AUG is guided to its correct position by the Shine Dalgarno sequence in the mRNA.
8. Which of the following blocks the peptidyl transferase of 80S eukaryotic ribosomes?
a) Chloramphenicol
b) Cycloheximide
c) Diphtheria toxin
d) Ricin
View Answer
Explanation: Chloramphenicol does not affect cytosolic protein synthesis in eukaryotes.
9. Which of the following catalyzes ADP-ribosylation of a diphthamide residue?
a) Chloramphenicol
b) Cycloheximide
c) Diphtheria toxin
d) Ricin
View Answer
Explanation: Diphtheria toxin catalyzes ADP-ribosylation of a diphthamide residue of eukaryotic elongation factor eEF2, thereby inactivating it.
10. Which of the following inhibits initiation at higher concentrations?
a) Chloramphenicol
b) Streptomycin
c) Diphtheria toxin
d) Ricin
View Answer
Explanation: Streptomycin, a basic tri-saccharide causes misreading of the genetic code at relatively low concentrations and inhibits initiation at higher concentrations.
Sanfoundry Global Education & Learning Series – Biochemistry.
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