This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Microbial Metabolism – Process of Protein Synthesis”.
1. The amino acids for protein synthesis is activated by the enzyme ______________
a) rna synthetase
b) aminoacyl-tRNA synthetase
c) tRNA synthetase
d) aminoacyl-mRNA synthetase
Explanation: The first step in protein synthesis is the activation of amino acids. The amino acids are activated by amino-acid activating enzymes called aminoacyl-tRNA synthetase.
2. The activation of amino acids requires energy.
Explanation: The activation of amino acids for protein synthesis requires energy in the form of ATP. There is a specific activating enzyme for each kind of amino acid.
3. tRNA has a _______________ structure.
Explanation: tRNA has a clover-leaf structure.The tRNA functions in protein synthesis to carry amino acids to, and recognize codons in, mRNA.
4. Transfer RNA is a single chain of ___________ nucleotides.
b) about 100
c) about 80
Explanation: Transfer RNA is a single chain of about 80 nucleotides that is folded back upon itself and held in a clover-leaf arrangement by means of hydrogen bonding due to complementary base pairing.
5. The terminal sequence of nucleotides in all tRNA is __________
Explanation: The terminal sequence of nucleotides is adenylic-cytidylic-cytidilic (ACC) and is found in all tRNA. The amino acid to be carried is linked to the terminal nucleotide containing adenine.
6.The tRNA carries amino acids to the ____________
Explanation: The tRNA carries amino acid to the mRNA attached to the surface of the ribosome. Here the amino acid is added to a growing polypeptide chain.
7. The ribosome of E.coli is made up of which two subunits?
a) 60S and 40S
b) 60S and 30S
c) 50S and 40S
d) 50S and 30S
Explanation: The ribosomes of E.coli have been studied extensively and have been found to consist of two subunits. The larger subunit is a 50S particle, while the smaller unit is a 30S particle.
8. S,the Svedberg unit is a measure of ____________________________
a) the size of the ribosome
b) the composition of the ribosome
c) how fast a particle sediments during ultracentrifugation.
d) how the subunits combine in a ribosome
Explanation: S is the Svedberg unit, a measure of how fast particle sediments during ultracentrifugation. The association of a 30S and 50S subunit to form a 70S ribosome shows that the sedimentation behavior of the 70S ribosome is not a simple addition of the units of the smaller particles.
9. Which of the following statement is correct?
a) The ribosome binds to any end of a mRNA
b) CTP is required for activation of amino acids
c) Activated amino acids bind to the 5’ end of a respective tRNA molecule
d) The protein chain dissociates from the last tRNA molecule
Explanation: The amino group of the amino acid on the second tRNA reacts with the active terminal carboxyl group on the amino acid of the first tRNA to form a dipeptide; the first tRNA is then released. The process is continued till the peptide chain is complete. Termination takes place at one of the nonsense codons and the chain dissociates from the last tRNA molecule.
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