Protein Synthesis

Q1: The anticodon of tRNA

A binds to rRNA

B binds to an amino acid

C binds to the Shine Dalgarno sequence

D binds to an mRNA codon

ANS:D - binds to an mRNA codon

No answer description is available.

Q2: On the ribosome, mRNA binds

A between the subunits

B to the large subunit

C to the small subunit

D none of these

ANS:C - to the small subunit

Why mRNA bind with small subunits of ribosomes? why not a larger sub-unit?

Q3: The peptidyl transferase reaction occurs

A on the large subunit

B on the small subunit

C between the subunit

D none of these

ANS:A - on the large subunit

No answer description is available.

Q4: The direction of amino acid transfer to the growing polypeptide chain is

A from the A (aminoacyl tRNA site) site to the P (peptidyl tRNA site) site on the ribosome

B from the P site to the A site on the ribosome

C from the A site to the E (exit tRNA site) site on the ribosome

D from the P site to the E site on the ribosome

ANS:B - from the P site to the A site on the ribosome

As we know, the ribosome has three active sites: the A site, the P site, and the E site.

The A site is the point of entry for the aminoacyl-tRNA (except for the first aminoacyl-tRNA, fMet-tRNAfMet, which enters at the P site).

The P site is where the peptidyl-tRNA is formed in the ribosome.

And the E site which is the exit site of the now uncharged tRNA after it gives its amino acid to the growing peptide chain.

So please explain the answer.

Q5: Type I proteins (plasma membrane) have a

A cleavage N- terminal signal sequence and a hydrophobic stop transfer sequence

B cleavaged N- terminal signal sequence that doubles as the membrane anchoring sequence

C multiple signal sequence and a hydrophobic stop transfer sequence

D multiple signal sequence that doubles as the membrane anchoring sequence

ANS:A - cleavage N- terminal signal sequence and a hydrophobic stop transfer sequence

No answer description is available.

Q6: Protein synthesis rates in prokaryotes are limited by the rate of mRNA synthesis. If RNA synthesis occurs at the rate of 50 nucleotides/sec, then rate of protein synthesis occurs at

A 10 amino acids/sec

B 17 amino acids/sec

C 25 amino acids/sec

D 50 amino acids/sec

ANS:B - 17 amino acids/sec

It has been found that the rate of transcription and translation are nearly similar.

Rate of transcription = 50nt/sec.
As the rate of transcription = rate of translation.

So, 50nt will code for 16.6 amino acids in a sec which is near to 17 amino acids/sec.

Q7: The ribosomes are composed of

A proteins

B RNA

C both (a) and (b)

D lipids

ANS:C - both (a) and (b)

No answer description is available.

Q8: Which site of the tRNA molecule binds to the mRNA molecule?

A Anticodon

B Codon

C Amino acid

D 5 prime end

ANS:A - Anticodon

No answer description is available.

Q9: A polysome could be best described as

A an active site of DNA synthesis.

B an active site of protein synthesis.

C an active site of lipid synthesis.

D all of the above.

ANS:B - an active site of protein synthesis.

The answer is B because in the rough endoplasmic reticulum there are free ribosomes polysomes which act as the most active site of protein synthesis.

Q10: Translation in prokaryotes begins by the formation of a 30S initiation complex between the

A 30S ribosomal subunit, mRNA, initiation factors and N-fMet tRNA

B 30S ribosomal subunit, tRNA and initiation factors

C 30S ribosomal subunit and mRNA only

D 30S ribosomal subunit, mRNA and initiation factors

ANS:A - 30S ribosomal subunit, mRNA, initiation factors and N-fMet tRNA

No answer description is available.

Q11: Signal peptide protein removal that is translocated across a membrane is accomplished by

A fMet aminopeptidase

B trypsin

C signal peptidase

D chymotrypsin

ANS:C - signal peptidase

No answer description is available.

Q12: Degenerated codon differs mostly in

A the identities of their second base

B the identities of their third base

C the wobble position

D both (b) and (c)

ANS:D - both (b) and (c)

No answer description is available.

Q13: The pathway of a tRNA during polypeptide elongation on the ribosome is

A A site → P site → E site

B P site → entry site → exit site

C A site → P site → entry site

D P site → A site → E site

ANS:A - A site → P site → E site

No answer description is available.

Q14: The first step in translation is

A binding of the two ribosomal subunits to each other

B binding of mRNA to the two ribosomal subunits

C binding of tRNA to the small ribosomal subunit

D binding of mRNA to the small ribosomal subunit

ANS:D - binding of mRNA to the small ribosomal subunit

No answer description is available.

Q15: Eukaryotic mRNA binding to the ribosomes is facilitated by __________ .

A the Shine Dalgarno sequence

B the 7-methyl guanosine cap

C tRNA

D poly A tail

ANS:B - the 7-methyl guanosine cap

Because Nawal sequence is not present in eukaryotes instead of that Kozak Sequence is there.

Q16: The structure in a bacterium that indicates an active site for protein synthesis is

A a chromosome.

B a cell membrane,

C a flagellum.

D a polysome.

ANS:D - a polysome.

No answer description is available.

Q17: How many bases of nucleic acid determine a single amino acid?

A Four

B One

C Two

D Three

ANS:D - Three

3 nucleotide encoded for single amino acid.

Q18: Which of the following has unusual bases?

A mRNA

B tRNA

C rRNA

D hnRNA

ANS:B - tRNA

No answer description is available.

Q19: Proteins contain __________ different amino acids, whereas DNA and RNA are composed of __________ different nucleotides

A 20,64

B 3,20

C 4,20

D 20,4

ANS:D - 20,4

Anyone, explain this clearly. Please.

Q20: The site of protein synthesis is

A Ribosome

B Nucleus

C Endoplasmic reticulum

D Chromosome

ANS:A - Ribosome

No answer description is available.

Q21: Which of the following is not a necessary component of translation?

A Anticodon

B mRNA

C Ligase

D Amino acid

ANS:C - Ligase

Ligases play an important role during DNA replication. It joins lagging strand.


Q22: Ribosomes select the correct tRNAs

A then bind to the appropriate mRNA

B solely on the basis of their anticodons

C depending on their abundance in the cytosol

D with the least abundant anticodons

ANS:B - solely on the basis of their anticodons

No answer description is available.

Q23: The lac operon contains the z, y and a structural genes

A encoding p-galactosidase, galactose permeases and thio-galactosidase transacetylase respectively

B encoding p-galactosidase and galactose permeases

C encoding P-galactosidase only

D None of the above

ANS:A - encoding p-galactosidase, galactose permeases and thio-galactosidase transacetylase respectively

No answer description is available.

Q24: Phosphorus is taken up by the cell during the process of

A carbohydrate synthesis.

B protein synthesis,

C lipid synthesis.

D ATP synthesis.

ANS:D - ATP synthesis.

No answer description is available.

Q25: Which of the following is not necessary for protein synthesis to occur, once transcription is completed?

A tRNA

B Ribosomes

C mRNA

D DNA

ANS:D - DNA

No answer description is available.

Q26: Amino acids are joined together into a protein chain by which of the following?

A Transfer RNA

B DNA polymerase

C Hydrogen bonds

D Messenger RNA

ANS:A - Transfer RNA

No answer description is available.

Q27: Which of the following amino acid starts all proteins synthesis?

A Glycine

B Proline

C Thymine

D Methionine

ANS:D - Methionine

Because initiation codon in Prokaryotic DNA is AUG which codes for Methionine.

Q28: Which of the following RNAs bind to an amino acid?

A mRNA

B tRNA

C rRNA

D hnRNA

ANS:B - tRNA

No answer description is available.

Q29: The site on a bacterial chromosome that marks the termination point for chromosome replication is called

A ter

B a stop codon.

C a stem-loop

D pau

ANS:A - ter

No answer description is available.

Q30: Which is required for protein synthesis?

A tRNA

B mRNA

C rRNA

D All of these

ANS:D - All of these

No answer description is available.

Q31: Processive synthesis is a characteristic feature of

A all DNA polymerases.

B DNA Pol III at a replication fork.

C removal of RNA primers on Okasaki fragments.

D DNA mismatch repair

ANS:B - DNA Pol III at a replication fork.

No answer description is available.

Q32: The growing polypeptide chain is released from the ribosomes when

A a chain terminating codon is reached

B a chain terminating tRNA binds to the ribosome

C the 7-methyl guanosine cap is reached

D the poly A tail is reached

ANS:A - a chain terminating codon is reached

No answer description is available.



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