1. Chapter 6 The Cell: Nucleus, Ribosomes

2. Nucleus Function contains eukaryotic cell’s genetic library Size
most genes in nucleus
some genes located in mitochondria & chloroplasts
Size
~ 5 microns (µm) in diameter

3. 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 molecules need to pass through?

6. 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

7. Nucleus structure Densely stained region = nucleolus Function
production of ribosomal subunits from rRNA & proteins
pass through nuclear pores to cytoplasm & combine to form ribosomes

10. Ribosomes Function Structure protein production
ribosomes contain rRNA & protein
composed of 2 subunits that combine to carry out protein synthesis
The genes for rRNA have the greatest commonality among all living things. There is very little difference in the DNA sequence of the rRNA genes in a humans vs. a bacteria.
Means that this function (building of a ribosome) is so integral to life that every cell does it almost exactly the same way.
Change a base and this changes the structure of the RNA which causes it to not function.

11. Types of Ribosomes Free ribosomes Bound 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

12. Ribosomes Prokaryotes & eukaryotes have different ribosomes
different size subunits
different proteins
can this difference be useful?

13. Prokaryote vs. eukaryote ribosomes
selective poisons can target the proteins of prokaryotic (bacterial) ribosomes = antibiotics

14. Any Questions??