BIOL 341 Chapter Notes - Chapter 15: Differential Centrifugation, Nuclear Pore, Protein Targeting
Document Summary
Eukaryotic cells are highly compartmentalized: techniques that helped scientists identify and understand material compartments: tem and differential centrifugation and genetic modification. Differential centrifugation: repeated centrifugation at progressively higher speeds will fractionate cell homogenates into their components. Separates cell components on the basis of size and density. Low speed: whole cells, nuclei, cytoskeletons: medium speed: mitochondria, lysosomes, peroxisomes, high speed: closed fragments of er, other small vesicles, very high speed: ribosomes, viruses, large macromolecules. Know table 15-1: main functions of membrane-enclosed compartments of a eukaryotic cell. Small molecules diffuse; large molecules (protein and rna) actively transported: proteins: imported using nuclear import receptor proteins in cytosol; rnas are exported. In cytosol: nuclear import protein recognizes nuclear signal sequence (zip code) and binds protein; complex is pulled through pore. Imported protein keeps its conformation: complex binds ran-gtp, import protein releases contents and exits, ran hydrolyzes gtp to gdp, active transport, nuclear localization depends on amino acid sequence of protein.
