NUCLEUSS

• What is usually the largest cellular structure?

  Nucleus
• What is the primary function of the nucleus?

  Control center for cellular operations
• How many different proteins can the nucleus direct the synthesis of?

  More than 100,000 different proteins
• What determines the structure and function of a cell?

  Sequence of nucleotides
• How many nuclei are usually present in a cell?

  Usually one per cell
• What is an exception to the rule of having one nucleus per cell?

  Skeletal muscle cell
• Which type of cell has no nucleus?

  Mature red blood cells
• How does the nucleus respond to environmental changes?

  Directs cellular responses to ECF changes
• What type of adjustments does the nucleus make for short-term responses?

  Changes in enzyme activity
• What type of adjustments does the nucleus make for long-term responses?

  Changes in enzymes produced
• What can result from long-term adjustments in the nucleus?

  Changes in cell structure from structural proteins
• When do long-term adjustments often occur?

  During growth, development, and aging
• What surrounds the nucleus and separates it from the cytoplasm?

  The nuclear envelope
• What is the function of the perinuclear space?

  It separates the two layers of the nuclear envelope
• What percentage of the nuclear surface do nuclear pores account for?

  About 10 percent
• What do nuclear pores permit?

  Chemical communication between the nucleus and cytosol
• What regulates the movement of ions and small molecules through nuclear pores?

  Proteins at the pores
• Can proteins or DNA freely cross the nuclear envelope?

  No, they cannot freely cross
• What is nucleoplasm?

  The fluid, gel-like substance of the nucleus
• What does nucleoplasm contain?

  It contains ions, enzymes, RNA, and DNA nucleotides
• What is the nuclear matrix?

  A network of fine filaments in nucleoplasm
• What role does the nuclear matrix play?

  It provides structural support and regulates genetic activity
• What are nucleoli?

  Transient nuclear organelles that synthesize ribosomal RNA
• What do nucleoli assemble?

  Ribosomal subunits
• How do ribosomal subunits enter the cytoplasm?

  By carrier-mediated transport at nuclear pores
• What are nucleoli composed of?

  RNA, enzymes, and histones
• When do nucleoli form around DNA?

  When producing ribosomal proteins and RNA
• In which types of cells are nucleoli most prominent?

  In cells that manufacture large amounts of proteins
• Which types of cells typically have prominent nucleoli?

  Liver, nerve, and muscle cells