GRE Subject Test: Biology : Understanding Ribosomes

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #8 : Other Organelles

Which of the following is true about eukaryote ribosomes?

Possible Answers:

Eukaryote ribosomes are 80S, with one large 60S subunit and one small 40S subunit

Eukaryote ribosomes are 80S, with one large 50S subunit and one small 30S subunit

Eukaryote ribosomes are 80S, with two large 60S subunits and one small 40S subunit

Eukaryote ribosomes are 80S, with one large 50S subunit and one small 40S subunit

Eukaryote ribosomes are 70S, with one large 60S subunit and one small 40S subunit

Correct answer:

Eukaryote ribosomes are 80S, with one large 60S subunit and one small 40S subunit

Explanation:

Eukaryotic ribosomes are 80S with one large 60S subunit and one small 40S subunit. Prokaryotic ribosomes are 70S, with one large 50S subunit and one small 30S subunit. "S" refers to the sedimentation coefficient (Svedberg), which is a particles sedimentation velocity for a given applied acceleration.

Example Question #9 : Other Organelles

Which of the following best describes the ribosome in terms of its structural components?

Possible Answers:

RNA-protein complex

Multimeric protein complex

RNA monomer

DNA-protein complex

Protein subunit

Correct answer:

RNA-protein complex

Explanation:

Ribosomes can be classified as ribonucleoproteins because the proteins are associated with ribonucleic acids (RNA). Thus, RNA-protein complex is the best descriptor. 

Example Question #10 : Other Organelles

Ribosomes are the organelle responsible for the translation of mRNAs into proteins. To do this, ribosomes translate the mRNA codons into amino acids which are joined to form a long polypeptide. The ribosome has a catalytic domain that is responsible for the formation of the peptide bonds between these amino acids. What is the name, i.e. the enzymatic classification, of this domain in the ribosome?

Possible Answers:

Peptidyl transferase 

Ester transferase

Peptidyl acylase

AminoATPase

Polymerase

Correct answer:

Peptidyl transferase 

Explanation:

Interestingly, ribosomes are one of the only examples of an RNA structure that has enzymatic activity. The primary enzymatic function of the ribosome is one of a peptidyl transferase; that is, the catalysis of peptide bond formation between amino acids as those acids are brought to the nascent strand. 

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