* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 17. Cytoskeleton Chapter 17. Cytoskeleton Chapter 17
Survey
Document related concepts
Cell culture wikipedia , lookup
Signal transduction wikipedia , lookup
Cellular differentiation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Microtubule wikipedia , lookup
Cell encapsulation wikipedia , lookup
Endomembrane system wikipedia , lookup
Extracellular matrix wikipedia , lookup
List of types of proteins wikipedia , lookup
Transcript
Chapter 17. Cytoskeleton • Cells are not “bags of enzymes”, but rather organized in three dimensions. • This organization is carried out by the cytoskeleton, the “bones and muscles” (and more) of cells. • Cells are thousands of times larger than a typical molecule. Therefore the cytoskeleton must logically be made by stringing together multiple smaller subunits. 1 Chapter 17. Cytoskeleton • Two things to keep an eye on: – The role of polymerization (and in some cases depolymerization) – The manner in which the cytoskeletal molecules interact with the rest of the cell. Often this is due to accessory proteins. 2 Chapter 17. Cytoskeleton • An overview of the three major components of the cytoskeleton. Intermediate filaments 3 Fig. 17.2 1 Chapter 17. Cytoskeleton • An overview of the three major components of the cytoskeleton. – Microtubules 4 Fig. 17.2 Chapter 17. Cytoskeleton • An overview of the three major components of the cytoskeleton. (Fig 17-2) – Actin Filaments 5 Fig. 17.2 Chapt 17. Intermediate Filaments • Intermediate filaments are mostly involved with strengthening organelles and cells. • Intermediate filaments are stable. 6 2 Chapt 17. Intermediate Filaments • The construction of intermediate filaments. (Fig 17-4) – The monomer consists of conserved and variable regions. – There are multiple kinds of monomers. – Different kinds of monomers differ primarily in the NH2 and COOH ends 7 Fig. 17.4 Chapt 17. Intermediate Filaments • The construction of intermediate filaments. (Fig 17-4) – Dimerization retains polarity, but the tetramer is antiparallel (and thus both ends are equivalent). 8 Fig. 17.4 Chapt 17. Intermediate Filaments • The construction of intermediate filaments. (Fig 17-4) – Packing into a filament. – The overlap between subunits contributes to the strength of the filament. 9 Fig. 17.4 3 Chapt 17. Intermediate Filaments • There are multiple kinds of chemically distinct intermediate filaments. 10 Fig. 17.6 Chapt 17. Intermediate Filaments • There are multiple kinds of chemically distinct intermediate filaments. – The keratins. Desmosomes Intermediate Filaments Hemidesmosomes 11 Fig. 17.5 Basement membrane Chapt 17. Intermediate Filaments • Evidence that the keratins really function as structural supports for epithelial cells: Epidermolysis bullosa simplex. Fig. 17.5 12 4 The cytoskeleton rearranges depending on the cell-cell junctions that are present in the cell. 13 Chapt 17. Intermediate Filaments • There are multiple kinds of chemically distinct intermediate filaments. (Fig 17-6) – Vimentin and related IF’s. • An example: certain Ifs hold muscle sarcomeres in place. 14 Chapt 17. Intermediate Filaments • There are multiple kinds of chemically distinct intermediate filaments. – Neurofilaments. Cell Body Axon AxonTerminus Dendrite 15 5 Chapt 17. Intermediate Filaments – The IF typically make much less use of accessory proteins than do the other 2 classes (MT and actin). – However, the accessory protein plectin cross links many IF to other cytoskeletal polymers and organelles. • Abnormal plectin results in symptoms of – Epidermolysis bullosa simplex – Muscular dystrophy – Neurodegeneration. 16 Chapt 17. Intermediate Filaments • There are multiple kinds of chemically distinct intermediate filaments. – Lamins. 17 Fig. 17.8 Chapt 17. Intermediate Filaments • Lamins: – Responsible for the integrity of the nuclear envelope. – Differ from most intermediate filaments in that they form a meshwork rather than a simple linear filament. – Also differ from other IFs because they can disassemble and reassemble. 18 6 Chapt 17. Intermediate Filaments • Summary: IFs …….. – Are primarily structural. – Have long lifetimes -- in most cases an IF is an IF forever. – Carry out different functions in different cells by being chemically distinct. 19 7