What is the primary function of the nucleolus in eukaryotic cells?

• A. It regulates the transport of molecules between the nucleus and cytoplasm.
• B. It is responsible for the production of ATP through cellular respiration.
• C. It is involved in the synthesis of lipids and detoxification processes.
• D. It is the site of ribosomal RNA synthesis and ribosome assembly.

Answer: (D)

Verified step by step guidance

1. Understand the role of the nucleolus within the eukaryotic cell. The nucleolus is a distinct structure found within the nucleus.
2. Recognize that the nucleolus is primarily involved in the synthesis of ribosomal RNA (rRNA). This is a crucial step in the formation of ribosomes, which are essential for protein synthesis.
3. Learn that ribosomes are composed of rRNA and proteins. The nucleolus assembles these components to form the ribosomal subunits.
4. Note that the nucleolus does not regulate transport between the nucleus and cytoplasm, produce ATP, or synthesize lipids. These functions are carried out by other organelles such as the nuclear envelope, mitochondria, and endoplasmic reticulum, respectively.
5. Conclude that the primary function of the nucleolus is the synthesis of rRNA and the assembly of ribosomal subunits, which are then transported to the cytoplasm for protein synthesis.