Question

What is true about ribosomes?
A. These are found only in eukaryotic cells.
B. These are self-splicing introns of some RNAs.
C. The prokaryotic ribosomes are 80S, where ‘S’ stands for sedimentation coefficient.
D. These are composed of ribonucleic acid and proteins.

Answer 1

Hint: Ribosomes are macromolecular machines, found within all living cells that perform biological protein synthesis. Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains.

Complete Answer:
Let us find the correct answer from the following,
Option A: ribosomes are found in both prokaryotic and eukaryotic cells. In prokaryotic cells 70S ribosomes are found and in the eukaryotic cell have 80s ribosomes. Therefore, this statement is false.

Option B: Self-splicing occurs for rare introns that form a ribozyme, performing the functions of the spliceosome by RNA alone. There are three kinds of self-splicing introns, Group I, Group II and Group III. Therefore, this statement is false.

Option C: In prokaryotes, 70S ribosomes are found and not 80S and S stands for sedimentation coefficient. Therefore, this statement is false.

Option D: A ribosome is a complex of RNA and protein and is, therefore, known as a ribonucleoprotein. It is composed of two subunits – smaller and larger. The smaller subunit, where the mRNA binds and is decoded and in the larger subunit, the amino acids get added. Ribosomes are specialized cell organelles and found in both prokaryotic and eukaryotic cells. Every living cell requires ribosomes for the production of proteins. The ribosome is composed of ribosomal RNAs and ribosomal protein. Therefore, this statement is true.

Thus, the correct option is D) These are composed of ribonucleic acid and proteins.

Note: The translation is a process of synthesizing proteins in a chain of amino acids known as polypeptides. It is the second part of the central dogma in genetics. It takes place in the ribosomes found in the cytosol or those attached to the rough endoplasmic reticulum.