Question

Which of the following pairs lacks the unit membrane?

• A. Nucleus and ER
• B. Mitochondria and chloroplast
• C. Ribosome and nucleolus
• D. Golgi body and lysosome

Answer 1

Answer: (C)

Ribosome and nucleolus

Ribosomes are the site of protein synthesis of the cell. It is composed of two subunits, a small subunit and a large subunit. The subunits act as an assembly line where the RNA from the nucleus is used to synthesize proteins from amino acids. Ribosomes are found freely floating or bound to a membrane or attached to mRNA molecules in a polysome. Unit membrane or cell membrane is absent in ribosomes. The nucleolus is the largest structure in the nucleus of eukaryotic cells where it primarily serves as the site of ribosome synthesis and assembly. Nucleoli also have other important functions like an assembly of signal recognition particles and playing a role in the cell's response to stress. Nucleoli are made of proteins and RNA and form around specific chromosomal regions. There is no unit membrane surrounding nucleolus.
So, the correct answer is option C.