Question

Ribosomes are granules made of
A. rRNA and tRNA
B. mRNA and tRNA
C. rRNA and proteins
D. mRNA and proteins

Answer 1

Hint: Ribosome, a molecule which is found in high numbers overall living cells and functions as a protein synthesis center. Ribosomes exist as both free particles in prokaryotes and eukaryotes and as particles clinging to the endoplasmic reticulum membranes in eukaryotes.

Complete answer:
Ribosomes are composed of ribosomal proteins and ribosomal RNA (rRNA). In prokaryotic cells, ribosomes are nearly 40% protein and 60% rRNA. In eukaryotes, ribosomes were about half of the protein and half of the rRNA. Ribosomes are normally composed of three or four rRNA molecules and up to 40 to 80 distinct ribosomal proteins. Each ribosome is composed of two subunits, a larger one and a smaller one, each of which has a characteristic shape.

The subunits typically are referred to in terms of their sedimentation rate, which is measured in Svedberg units (S), in a centrifugal field. The small and large subunits of eukaryotes are designated the 40S and 60S, respectively, while prokaryotes contain a small 30S subunit and a large 50S subunit. Ribosomes connect amino acids with each other in the order defined by the messenger RNA codons to create polypeptides. The ribosome is a very complex cellular unit. It is composed primarily of specialized RNA known as ribosomal RNA as well as hundreds of distinct proteins (the actual figure varies marginally among life forms).

So, the correct answer is option (C).

Additional information:
Ribosomes are the locations where data encoded in the genetic code is processed into protein molecules. Ribosomal molecules of RNA messenger decide the sequence of transfer of RNA molecules attached to nucleotide triplets (codons). The sequence of the tRNA molecules eventually determines the sequence data of the amino acids. The newly designed proteins separate themselves from the site of the ribosome and relocate to many other areas of the cell to be used.

Note: The tiny particles that later became known as ribosomes were first established in 1955 by George E. Palade, a Romanian-born American cell biologist. The ribosomes throughout the cells are surprisingly abundant. The size of the ribosomes inside the cells varies according to the type of cells and on conditions such as whether cells rest or multiply.