November 17, 2010

Q&A: RNA and Their Different Roles in Protein Synthesis

Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and DNA are nucleic acids. Along with lipids, proteins, and carbohydrates, nucleic acids constitute one of the four major macromolecules essential for all known forms of life.

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find more useful one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
RNA roles in nature
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

RNA roles in nature

Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA, RNA is found in nature as a single strand folded onto itself, rather than a paired double strand. Cellular organisms use messenger RNA (mRNA) to convey genetic information (using the nitrogenous bases of guanine, uracil, adenine, and cytosine, denoted by the letters G, U, A, and C) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome.

Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function in which RNA molecules direct the synthesis of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) then links amino acids together to form coded proteins.

MCQ: clinical scenario

Three types of RNA involved in comprising the structural and functional core for protein synthesis, serving as a template for translation, and transporting amino acid, in that order respectively, are:

a) mRNA, tRNA, rRNA
b) rRNA, tRNA, mRNA
c) tRNA, mRNA, rRNA
d) tRNA, rRNA, mRNA
e) rRNA, mRNA ,tRNA

MCQ questions & answers on medicalnotes.info

MCQ: answer

The correct answer is E.

MCQ: explanation

rRNA's serve a structural and functional role in protein synthesis as a component of the ribosome. The transpeptidization reaction has been shown to be caused by rRNA. mRNA is transcribed from DNA to be used as a template for protein synthesis. The tRNA's bring the correct amino acid into the protein synthesis process.

Also see this separate Q&A article, Components of Protein Biosynthesis.

Reference(s)
1). University of Utah. 2015. RNA: The Versatile Molecule. Available online: https://learn.genetics.utah.edu/content/basics/rna/
2). Cooper GC, Hausman RE (2004). The Cell: A Molecular Approach (3rd ed.). Sinauer. pp. 261–76, 297, 339–44. ISBN 978-0-87893-214-6. OCLC 174924833.
3). Shukla RN (2014). Analysis of Chromosomes. ISBN 978-93-84568-17-7.

No comments:

Post a comment

Got something to say? We appreciate your comments: