GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Ribosome and tRNA Structure

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Ribosome And T Rna Structure

To which of the following structures in a typical molecule of tRNA is an amino acid attached?

Possible Answers:

Variable loop

CCA tail

Anticodon loop

D loop

Correct answer:

CCA tail

Explanation:

Amino acids are attached to the CCA tail of a tRNA. These are found at the 3' end of tRNA molecules and are important for recognition by aminoacyl tRNA synthetases (enzymes that actually attach the amino acids to the tRNA). The anticodon loop, as the name suggests, contains the anticodon, which will be important during translation for recognizing mRNA sequences. The D-loop and the variable loop are other portions of the tRNA that are important for maintaining structure and recognition.

Example Question #2 : Help With Ribosome And T Rna Structure

Chloramphenicol prevents protein translation by which of the following mechanisms?

Possible Answers:

It blocks the translocation reaction on ribosomes

It blocks the binding of aminoacyl tRNA to the A site of the ribosome

It blocks the peptidyl transferase reaction on ribosomes

It blocks initiation of RNA chains by binding to RNA polymerase

Correct answer:

It blocks the peptidyl transferase reaction on ribosomes

Explanation:

Tetracycline blocks the binding of aminoacyl tRNA to the A site of the ribosome.

Cyclohexamide blocks the translocation reaction on ribosomes.

Rifamycin blocks the initiation of RNA chains by binding to RNA polymerase.

Chloramphenicol blocks the pepidyl transferase reaction on the ribosome.

Example Question #3 : Help With Ribosome And T Rna Structure

During translation, which site in the ribosome allows for tRNA moelcules to enter the complex? 

Possible Answers:

E site

R site

A site

P site

Correct answer:

A site

Explanation:

The ribosomal complex has three sites where tRNA moelcules can be oriented during the process of translation: the A site, the P site, and the E site. During polypeptide elongation, a tRNA with an attached amino acid will enter at the A site. It will then move to the P site, now holding the growing polypeptide chain. All tRNAs no longer holding an amino acid will exit the ribosome at the E site.

Example Question #4 : Help With Ribosome And T Rna Structure

On which of the following molecules could you find an anticodon?

Possible Answers:

rRNA

miRNA

mRNA

tRNA

Correct answer:

tRNA

Explanation:

In order to make sure that the proper amino acid is added to the growing polypeptide chain, an anticodon found on the tRNA carrying the amino acid must be a match for the codon found on the mRNA.

Example Question #5 : Help With Ribosome And T Rna Structure

Which of the following most accurately describes the chronological order of ribosome biogenesis in eukaryotes?

Possible Answers:

Ribosomal proteins are translated in the nucleous and transported to the cytoplasm. At the same time, rRNA genes are being rapidly transcribed in the nucleolus. rRNA and ribosomal proteins form the 60S and 40S subunits in the cytoplasm, where they join to form a functional ribosome. 

Ribosomal proteins are translated in the cytoplasm and transported to the nucleolus. At the same time, rRNA genes are being rapidly transcribed in the cytoplasm. rRNA and ribosomal proteins form the 60S and 40S subunits in the cytoplasm. 

Ribosomal proteins are translated in the cytoplasm and transported to the nucleolus. At the same time, rRNA genes are being rapidly transcribed in the nucleolus. rRNA and ribosomal proteins form the 60S and 40S subunits in the nucleolus and are then transported to the cytoplasm for functional ribosome assembly. 

Ribosomal proteins are translated in the cytoplasm. At the same time, rRNA genes are being rapidly transcribed in the nucleolus. rRNA is transported to the cytoplasm where the rRNA and ribosomal proteins form the 60S and 40S ribosomal subunits. 

Ribosomal proteins are translated in the cytoplasm and transported to the nucleolus. At the same time, rRNA genes are being rapidly transcribed in the nucleolus. rRNA and ribosomal proteins form the 50S and 30S subunits in the nucleolus and are then transported to the cytoplasm for functional ribosome assembly. 

Correct answer:

Ribosomal proteins are translated in the cytoplasm and transported to the nucleolus. At the same time, rRNA genes are being rapidly transcribed in the nucleolus. rRNA and ribosomal proteins form the 60S and 40S subunits in the nucleolus and are then transported to the cytoplasm for functional ribosome assembly. 

Explanation:

Ribosomal proteins are translated in the cytoplasm and rRNA genes are transcribed in the nucleolus. Following protein translation, these proteins enter the nucleus through nuclear pores and localize to the nucleolus. Here, transcribed rRNA associates with the ribosomal proteins to form the 60S and 40S eukaryotic ribosomal subunits. Prokaryotes have 50S and 30S subunits. The ribosomal subunits then translocate to the cytoplasm where they join together to form fully functional ribosomes. 

Example Question #6 : Help With Ribosome And T Rna Structure

How many ribosomal binding sites are there and what are their functions? 

Possible Answers:

There are three sites. A site binds peptidyl-tRNA, P site binds aminoacyl-tRNA, E site binds free tRNA before ribosomal exit

There are three sites. A site binds free tRNA before ribosomal exit, P site binds aminoacyl-tRNA, E site binds peptidyl-tRNA 

There are two sites. A site binds free tRNA before ribosomal exit, P site binds peptidyl-tRNA 

There are three sites. A site binds aminoacyl-tRNA, P site binds peptidyl-tRNA, E site binds free tRNA before ribosomal exit

There are two sites. A site binds free tRNA before ribosomal exit, P site binds aminoacyl-tRNA

Correct answer:

There are three sites. A site binds aminoacyl-tRNA, P site binds peptidyl-tRNA, E site binds free tRNA before ribosomal exit

Explanation:

The correct answer is there are three sites. A site binds aminoacyl-tRNA, P site binds peptidyl-tRNA, E site binds free tRNA before ribosomal exit. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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