Question

Which organelle contains ribosomal RNA and is involved in the production of ribosomes?

• A. Endoplasmic reticulum
• B. Nucleus
• C. Nucleolus
• D. Golgi apparatus

Answer 1

Answer:

C. Nucleolus

The Nucleolus: A Key Player in Ribosome Synthesis

Location and Structure:

• The nucleolus is a dense structure found inside the nucleus of eukaryotic cells.

• It lacks a membrane-bound organelle, meaning it is not enclosed by its own membrane.

• It is the largest structure within the nucleus.

Primary Function: Ribosome Biogenesis

• The nucleolus is primarily responsible for the synthesis of ribosomal RNA (rRNA).

• It also plays a crucial role in the assembly of ribosomes. This process involves combining rRNA with ribosomal proteins to form the large and small ribosomal subunits.

• These subunits are then exported from the nucleus to the cytoplasm, where they combine to form functional ribosomes during protein synthesis.

Composition:

• The nucleolus is composed of RNA and protein.

• The main components are:

  • Ribosomal RNA (rRNA): This is the RNA molecule that forms the structural and catalytic core of the ribosome.

  • Proteins: Including enzymes involved in rRNA synthesis and processing, as well as proteins that will form the ribosomal subunits.

Significance in Cell Biology:

• Ribosomes are essential for protein synthesis, making the nucleolus vital for cell function and survival.

• The size and activity of the nucleolus can vary depending on the cell's metabolic state and its need for protein synthesis. Cells with high rates of protein synthesis (e.g., rapidly growing cells) typically have larger and more active nucleoli.

• The nucleolus is also implicated in other cellular processes, including cell cycle regulation and response to stress.