Chapter 5.3 The Cell: Nucleus, Ribosomes AP Link—Ch04: John Kyrk Organelle Review AP Link—Ch04: Genetic Science Learning Center (organelle review)

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 AP Movie—Ch 04: 100 Greatest Discoveries—Cell Nucleus

What kind of molecules need to pass through? 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 AP Movie—Ch 04: Ameoba Nucleus What kind of molecules need to pass through?

If you think this looks complicated, this is how proteins are made…wait until Chapter 12!

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

Nucleus structure Densely stained region in nucleus is nucleolus Function production of ribosomal subunits from rRNA & proteins pass through nuclear pores to cytoplasm & combine to form ribosomes AP Movie—Ch 04: Nucleus Structure

AP Link—Ch 04: Cytoplasmic Streaming

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.

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

Ribosomes Prokaryotes & eukaryotes have different ribosomes different size subunits different proteins

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

Structure of Ribosomes 2000 | 2009 Structure of Ribosomes Ramakrishnan, Steiz, and Yonath determined the structure of the 30S ribosome Venkatraman Ramakrishnan Thomas Steitz Ada Yonath

Start asking… I know you have some! Any Questions?? Start asking… I know you have some!