Nucleolus

Definition

The nucleolus is a dense, spherical structure found within the nucleus of eukaryotic cells. It is primarily involved in the synthesis and assembly of ribosomes.

5 Must Know Facts For Your Next Test

1. The nucleolus is not membrane-bound and resides within the nucleus.
2. It is responsible for producing and assembling ribosomal RNA (rRNA) and ribosome subunits.
3. The size of the nucleolus can vary depending on the cell's activity, especially during periods of active protein synthesis.
4. It contains three distinct regions: the fibrillar center, dense fibrillar component, and granular component.
5. The nucleolus plays a role in cellular stress responses by regulating processes like cell cycle control and apoptosis.

Review Questions

• What is the primary function of the nucleolus?
• How does the size of the nucleolus change with cellular activity?
• Name the three distinct regions found within the nucleolus.

Related terms

Nucleus:

A membrane-bound organelle that contains genetic material (DNA) organized into chromosomes.

Ribosome:

A molecular machine that synthesizes proteins by translating messenger RNA (mRNA).

rRNA (ribosomal RNA): A type of RNA that combines with proteins to form ribosomes, essential for protein synthesis.