High School Biology : Understanding Ribosome and tRNA structure

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Ribosome And T Rna Structure

What is the purpose of tRNA in translation?

Possible Answers:

It transfers the mRNA to the ribosome for translation

It carries the newly formed protein to the Golgi apparatus in order to be modified

It carries an amino acid to the ribosome in order to be added to the growing polypeptide

It adds to proteins in order to form the ribosomes

Correct answer:

It carries an amino acid to the ribosome in order to be added to the growing polypeptide

Explanation:

tRNA is responsible for bringing individual amino acids to the ribosome in order to be incorporated into the protein. It has an anticodon that attaches to a specific codon found on the mRNA. Once the tRNA and mRNA are bound, a peptide bond if formed between the amino acid residue from the tRNA and the amino acid chain on the ribosome. This is how amino acids are added to the growing protein.

Example Question #2 : Understanding Ribosome And T Rna Structure

In eukaryotes, what are the sizes of the ribosomal subunits?

Possible Answers:

30S and 50S

30S and 60S

40S and 60S

40S and 50S

30S and 70S

Correct answer:

40S and 60S

Explanation:

The small subunit of eukaryotic ribosomes is 40S and the large subunit is 60S. These combine to form the ribosome, which is 80S in sedimentary size.

For prokaryotes, the ribosome subunits are 30S and 50S to form a total of 70S total unit.

Example Question #3 : Understanding Ribosome And T Rna Structure

What portion of the ribosome does mRNA attach to during the beginning of translation?

Possible Answers:

The large subunit

The small subunit

The tRNA chain

The active site

Correct answer:

The small subunit

Explanation:

At the beginning of translation, mature mRNA will travel into the cytosol and attach to the small ribosomal subunit first. This signals the larger subunit to come and attach in order to begin elongation of the polypeptide.

Note that ribosomes do not have an "active site." Active sites are the region of a protein that will bind a substrate and initiate a catalytic change. Ribosomes are not proteins; they are composed of ribosomal RNA (rRNA), and thus do not have active sites.

Example Question #4 : Understanding Ribosome And T Rna Structure

Anticodons pair with mRNA codons during which stage of protein synthesis?

Possible Answers:

Translation

Transfection

Transformation

Transcription

Transfusion

Correct answer:

Translation

Explanation:

During translation, the ribosome binds to mRNA and to the appropriate tRNAs. On the ribosome, the mRNA condons are translated into the amino acid sequence of a protein with the help of the tRNA anticodons.

Transcription refers to the synthesis of an RNA molecule from a DNA template. Transformation occurs when a bacterium is able to absorb and incorporate genetic material from the extracellular environment. Transfusion is the transfer of blood from a donor to a recipient. Transfection is the infection of bacteria by phage DNA.

Example Question #15 : Proteins

Where is the anticodon located?

Possible Answers:

On the tRNA

On the DNA

On the mRNA

On the ribosome

On the new protein being made

Correct answer:

On the tRNA

Explanation:

The tRNA carries the amino acid specified by its anticodon. The anticodon base pairs with the codon on the mRNA to ensure the correct amino acid is added to the new protein that is being made. Thus there is a specific tRNA for each codon.

Example Question #5 : Understanding Ribosome And T Rna Structure

What is the composition of ribosomes?

Possible Answers:

rRNA only

rRNA and protein

mRNA only

protein only

DNA only

Correct answer:

rRNA and protein

Explanation:

Ribosomes are made up of rRNA and proteins. rRNA synthesis, and ribosome assembly takes place in the nucleolus. 

Example Question #17 : Proteins

Which of the following best represents where the triplet anticodon is most commonly found?

Possible Answers:

tRNA

rRNA

mRNA

DNA

Correct answer:

tRNA

Explanation:

Transfer RNA—tRNA—is a small folded RNA molecule (i.e. 80-90 nucleotides in length) utilized during translation. On the other hand, tRNA serves as a link between the messenger RNA—mRNA—and the growing protein’s amino acid sequence. The tRNA carries an amino acid to the ribosome directed by the mRNA’s codon—a three-nucleotide sequence. The tRNA carries an anticodon, which is also a three-nucleotide sequence that matches the genetic code, which complements the mRNA. Last, rRNA is associated with the ribosome. 

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