IMAT 2013 Q34 [Ribosomes]

Which statement about ribosomes is NOT correct?

A. Ribosomes are involved in protein synthesis.
B. Ribosomes can be found in the cytoplasm.
C. Ribosomes can be found on rough endoplasmic reticulum (RER).
D. Ribosomes can have RNA associated with them.
E. Ribsosomes can carry out transcription.

The answer to this question is choice E.

Let’s dissect each of the choices and analyze whether or not they are correct associations with ribosomes:

  • Ribosomes are involved in protein synthesis. This is a correct statement, since ribosomes along with its 2 subunits (large and small subunits) make up the molecular machinery that is involved in translating mRNA into peptide chains.

  • Ribosomes can be found in the cytoplasm. This is another correct statement, since ribosomes can be seen in different areas within the cell. It can be free, floating in the cytoplasm or it can also be found outside of the nuclear envelope. Ribosomes are also commonly found in the endoplasmic reticulum, which gives rise to the rough endoplasmic reticulum.

  • Ribosomes can be found on rough endoplasmic reticulum (RER). This is another true statement, as mentioned earlier. The reason it is called “rough” endoplasmic reticulum is secondary to the presence of ribosomes bound to the organelle.

  • Ribosomes can have RNA associated with them. This is a correct statement. A ribosome is basically made up of RNA and proteins. Specifically, ribosomes contain 2 subunits called the large and small subunits, which are 2 separate RNA-complexes. The mRNA can be found in between these 2 subunits.

  • Ribosomes can carry out transcription. This is a FALSE statement. The ribosomes are involved in the process of translation, but NOT in the process of transcription. Transcription is the process of copying a certain DNA sequence in to an RNA copy. The process of transcription is mediated by RNA polymerases and not ribosomes.

Thus, the only correct answer is choice E, since it is not a correct association with ribosomes.