Eukaryotic cells contain membrane-bound nuclei that house the cell’s DNA. The nucleus is the control center of the cell. The nucleus of living cells contains the genetic material that determines the entire structure and function of that cell.

The boundary of the nucleus is called the nuclear envelope. It consists of two phospholipid bilayers: an outer membrane and an inner membrane. The nucleus is also where we find the nucleolus. The nucleolus is a condensed region of chromatin where ribosome synthesis occurs. Nuclear pores allow substances to enter and exit the nucleus. For example, proteins with a nuclear localization signal are recognized by nuclear pores for entry into the nucleus.

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Key Points

• Eukaryotic cells contain membrane-bound nuclei that house the cell’s DNA.

• The nucleus is the control center of the cell, containing the genetic material that determines the entire structure and function of that cell.

Key Terms

nucleus: membrane-bound control center of the eukaryotic cell, contains genetic material

nuclear envelope: a boundary of the nucleus, made of a phospholipid bilayer

nuclear pores: pores in nuclear envelope that allows substances to go in and out

nucleolus: a condensed region of chromatin where ribosome synthesis occurs

eukaryotic: are organisms whose cells have a nucleus enclosed within membranes

phospholipid bilayer: consists of two layers of phospholipids, with a hydrophobic, or water-hating, interior and a hydrophilic, or water-loving, exterior

chromatin: DNA and proteins that condense to form chromosomes

ribosomes: made of RNA and produce proteins