Question

The ribosomes of bacteria, mitochondria, prokaryotes, and chloroplast are of
A) 50S type
B) 80S type
C) 70S type
D) 30S type

Answer 1

Hint: Ribosomes are of two types, 70S and 80S ribosomes. 70S ribosomes are present in prokaryotic cells and 80S ribosomes are present in eukaryotic cells. Ribosomes are made up of two subunits. 70S ribosomes are made up of 50S and 30S subunits while 80S ribosomes are made up of 60S and 40S subunits.80S ribosomes are present in the cytoplasm of eukaryotic cells and are absent in bacteria.

Complete answer:
Membrane bound cell organelles are absent in prokaryotic cells, however it has ribosomes which participate in protein synthesis. The prokaryotic ribosomes are of 70S type, different from eukaryotic ribosomes which are of 80S type. Eukaryotic cells organelles (mitochondria, chloroplast) have their own machinery for protein synthesis and also their own ribosomes which are similar to the prokaryotic ribosome.

Hence, the correct answer is option (C), 70S type.

Additional Information: The ribosome is a cytoplasmic nucleoprotein particle and its major function is to serve as the site of mRNA translation and protein synthesis. The ribosome has a mass of about 2.5MDa.Ribosomal proteins enter in nucleolus and combine with the four rRNA strands to make subunits which make complete ribosomes.
Ribosomes are synthesized in cytoplasm through a process which is called transcription of several ribosomal gene operons. In eukaryotic cells, the process takes place in cytoplasm as well as in nucleolus. The process involves function of over 200 proteins in the synthesis and processing of four rRNA, as well as assembly of rRNA with ribosomal protein.

Note: Ribosomes were discovered by cell biologist George Emil Palade, in the year 1950, by using an electron microscope "ribosome" was coined by the scientist Richard B. Robert in the year 1950. They won the Nobel Prize for their discovery. In the name ribosome, “rib” comes from ribonucleic acid which provides instructions for protein synthesis.