Chapter 7. The Cell: Nucleus, Ribosomes

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Chapter 7.The Cell Nucleus, Ribosomes
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Nucleus

• Function
• contains eukaryotic cells genetic library
• most genes in nucleus
• some genes located in mitochondria
  chloroplasts
• Size
• 5 microns (µm) in diameter

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Nucleus structure

• Structure
• separated from cytoplasm by a double membrane,
  nuclear envelope
• double membrane is fused in spots forming pores
• allows large macromolecules particles to pass
  through

What kind of moleculesneed to pass through?
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Nucleus structure

• Within nucleus, DNA organized into fibrous
  material, chromatin
• in normal cell appears as diffuse mass
• When cell prepares to divide, chromatin fibers
  coil up as separate structures, chromosomes

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Nucleus structure

• Densely stained region nucleolus
• Function
• production of ribosomal subunits from rRNA
  proteins
• pass through nuclear pores to cytoplasm
  combine to form ribosomes

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Ribosomes

• Function
• protein production
• Structure
• ribosomes contain rRNA protein
• composed of 2 subunits that combine to carry out
  protein synthesis

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Types of Ribosomes

• Free ribosomes
• suspended in cytosol
• synthesize proteins that function within cytosol
• Bound ribosomes
• attached to outside of endoplasmic reticulum
• synthesize proteins for export or for membranes

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Ribosomes

• Prokaryotes eukaryotes have different ribosomes
• different size subunits
• different proteins
• can this difference be useful?

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Prokaryote vs. eukaryote ribosomes
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Any Questions??