Question

Where are ribosomes synthesized?

Answer 1

Hint: Ribosome is the organelle, where the proteins are synthesized. Ribosomes are found freely in the cytoplasm in the prokaryotic cell. In the eukaryotes, ribosomes remain attached to the rough endoplasmic reticulum. Nucleolus is the special dense region in the typical eukaryotic cell. Nucleolus is responsible for the packaging and assembly of the proteins.

Complete answer:
Nucleolus is the special dense region in the typical eukaryotic cell. Nucleolus is composed of RNA and protein. Nucleolus itself is the site of ribosome synthesis in a eukaryotic cell. Ribosomes are synthesized in the cytoplasm through the transcription of multiple ribosome gene operons in a prokaryotic cell. The process of ribosome synthesis occurs inside the nucleolus which plays a vital role in sensing cellular stress and assembling ribosomes. Ribosome biogenesis is known as the process of making ribosomes. This process involves the coordinated function of over $200$ proteins in the synthesis and processing of the three prokaryotic or four eukaryotic rRNAs and the assembly of these rRNAs with the ribosomal proteins as well. Mostly, the ribosomal proteins fall into various energy consuming enzyme families. The enzymes include RNA helicases, AAA-ATPases, GTPases and kinases. In the process of ribosome production and maintenance, about $60\%$ of the cell’s energy is spent. This process is very tightly regulated and it is closely linked to other cellular activities like growth and division. After the assembly of proteins and formation of ribosomes, it is exported out to the cytoplasm.

Note:
In eukaryotes, $5S$ rRNA is synthesized by RNA polymerase $III$ whereas other eukaryotic rRNA molecules are transcribed by RNA polymerase $I$. It is speculated that ribosome biogenesis predates cells. Also genes and cells evolved to enhance the reproductive capacity of ribosomes. In the cell mitochondria is the organelle responsible for ATP synthesis. Smooth endoplasmic reticulum plays a role for the synthesis of hormones and lipids in the cell. Chloroplast is the site for photosynthesis (present only in plant cells). Golgi apparatus is responsible for the transport of proteins and sorting assembly.